# 10. - SIP SDP - Session Descripton Protocol

#### SIP SDP

SIP SDP stands for Session Description Protocol and is a protocol used to describe multimedia sessions for the purposes of session initiation, control, and management. In the context of SIP, SDP is typically used in the body of SIP messages to describe the characteristics of media streams being offered or negotiated in a SIP session. This includes information such as the type of media, codec, bandwidth, and IP addresses and ports for the media streams. SDP is an important part of the SIP protocol because it allows endpoints to negotiate and establish media sessions for audio, video, and other types of multimedia content.

There are a lot of fieldes availabble in SDP and some are mandatory (shown here in blue). New fields can be added as needed. if an agent doesn't understand a field it simply ignores it.

![image.png](https://wiki.tinod.net/uploads/images/gallery/2023-05/scaled-1680-/t081mIiEHRqe95rB-image.png)

#### MIME

MIME stands for Multipurpose Internet Mail Extensions, which is a standard that extends the format of email messages to support text in character sets other than ASCII, as well as attachments of audio, video, images, and application programs. In the context of SIP SDP (Session Description Protocol), MIME is used to specify the media type and format of the SDP body in the SIP message. The MIME type for SDP is "application/sdp". The SDP body contains information about the media streams to be used for the session, such as the codecs, transport protocols, and media formats to be used. The MIME type allows the receiving endpoint to determine how to handle the SDP body in the SIP message.

```
INVITE sip:bob@biloxi.com SIP/2.0
Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bK776asdhds
Max-Forwards: 70
To: Bob <sip:bob@biloxi.com>
From: Alice <sip:alice@atlanta.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Contact: <sip:alice@pc33.atlanta.com>
User-Agent: BriaX 3.5.5 build 81887
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, MESSAGE, SUBSCRIBE, INFO
Allow-Events: presence, message-summary, refer, dialog
Session-Expires: 3600;refresher=uas
Content-Type: application/sdp
Content-Length: 283

v=0
o=- 123456 789012 IN IP4 pc33.atlanta.com
s=SIP Call
c=IN IP4 192.0.2.1
t=0 0
m=audio 49170 RTP/AVP 0 8 18 3 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:3 GSM/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
m=video 49172 RTP/AVP 31 34
a=rtpmap:31 H261/90000
a=rtpmap:34 H263/90000

```

In this example, the header includes the following fields:

<details id="bkmrk-expand-to-view-heade"><summary>Expand to view Header description</summary>

- Via: Indicates the transport protocol, IP address, and port number used for the request. In this case, it is a UDP transport protocol and the IP address is pc33.atlanta.com.
- Max-Forwards: Indicates the maximum number of times the request can be forwarded before it is discarded.
- To: Contains the display name and SIP URI of the destination user.
- From: Contains the display name and SIP URI of the source user, along with a unique identifier (tag) for the request.
- Call-ID: Unique identifier for the call.
- CSeq: Sequence number for the request.
- Contact: Indicates the SIP URI that can be used to reach the sender of the request.
- User-Agent: Indicates the user agent that generated the request.
- Allow: Lists the SIP methods that the user agent is able to handle.
- Allow-Events: Lists the types of events that the user agent can generate.
- Session-Expires: Indicates the duration of the session in seconds and the refresher type (in this case, uas).

</details>The SDP message in the body of the request describes the media capabilities of the sender and includes the following information:

- `v` (Protocol version): Indicates the protocol version of the session description. In this case, it is 0.
- `o` (Origin): Specifies the originator of the session and a unique identifier for the session. The fields include username, session identifier, session version number, and network type (IN for Internet) and address type (IP4 for IPv6). O=&lt;username&gt; &lt;sess-id&gt; &lt;sess-version&gt; &lt;nettype&gt; &lt;addrtype&gt; &lt;unicast-address&gt;
    
    The nettype and addrtype fields can take various values depending on the network protocol being used. Some of the options for the nettype field include:
    
    
    - IN: Internet
    - AT: Atmosphere
    - FI: FIP Snooping
    - Token-Ring: IBM Token Ring Network
    
    Some of the options for the addrtype field include:
    
    
    - IP4: IPv4 address
    - IP6: IPv6 address
    - MAC: MAC address
    - NSAP: Network Service Access Point
    - E.164: E.164 telephone number
- `s` (Session name): Specifies a human-readable session name.
- `c` (Connection information): Specifies the connection information for the session. In this case, it is the IP address 192.0.2.1 - This field specifies the network address type IP4 or IP6 and the connection address IP Address or hostname of the media stream RTP, there are different types of connection information fields: 
    - c=IN IP4 192.0.2.1: This specifies that the media stream will use IPv4 and the IP address is 192.0.2.1
    - c=IN IP6 ::1: This specifies that the media stream will use IPv6 and the IP address is ::1 (loopback address).
    - c=IN IP4 192.168.1.100/255: This specifies that the media stream will use IPv4 and the IP address is 192.168.1.100, with a subnet mask of 255.255.255.0.
- `t` (Timing): Specifies the start and stop times of the session. In this case, it is set to 0, which means the session is not limited by time.
- `m` (Media): Specifies the media type (audio), the port number (1234), and the transport protocol (RTP/AVP). There can be multiple media fields in an SDP message. 
    - m=audio 49170 RTP/AVP 0 8: This specifies an audio stream on port 49170 using RTP/AVP protocol, with two codecs: PCMU (payload type 0) and PCMA (payload type 8).
    - m=video 51372 RTP/AVP 31 34: This specifies a video stream on port 51372 using RTP/AVP protocol, with two codecs: H.263 (payload type 31) and H.264 (payload type 34).
- `a` (Attribute): Specifies additional attributes for the session. In this case, it specifies the RTP payload type for each codec (0 for PCMU, 8 for PCMA, and 101 for telephone-event), the codec names (PCMU, PCMA, and telephone-event), and the sampling rate (8000). The last line specifies the allowable range of event codes for the telephone-event codec. there can be multiple attribute fields in an SDP message
- a=rtpmap:0 PCMU/8000: This specifies the codec for payload type 0 as PCMU with a sampling rate of 8000 Hz.
- a=rtpmap:31 H263/90000: This specifies the codec for payload type 31 as H.263 with a clock rate of 90000 Hz.
- a=sendrecv: This specifies that the media stream is bi-directional (send and receive).
- a=rtcp-mux: This specifies that the RTP and RTCP packets are multiplexed on the same port.

##### RTPMAP

In the context of SDP, RTPMAP (RTP Mapping) is an attribute used to map a particular codec to an RTP payload type number. RTP is the Real-time Transport Protocol, which is used to transmit audio and video over IP networks. RTP uses payload types to identify the format of the data being transmitted.

The RTPMAP attribute provides a way for the sender to signal the receiver about the payload type numbers and the corresponding codecs being used. The attribute specifies the encoding name, the clock rate of the codec, and the number of audio channels being transmitted.

The syntax for the RTPMAP attribute is as follows:

<div class="bg-black rounded-md mb-4" id="bkmrk--2"></div>```
a=rtpmap:<payload type> <encoding name>/<clock rate>[/<encoding parameters>]
```

where:

- `<payload type>` is an integer value representing the payload type number.
- `<encoding name>` is a string that identifies the codec being used, such as "PCMU" for G.711 mu-law audio or "H264" for H.264 video.
- `<clock rate>` is an integer value indicating the clock rate of the codec, in Hz.
- `<encoding parameters>` is an optional string that specifies additional parameters for the codec, such as packetization mode or frame size.

Here is an example of an RTPMAP attribute for G.711 mu-law audio:

```
a=rtpmap:0 PCMU/8000
```

This specifies that payload type 0 is used for G.711 mu-law audio, with a clock rate of 8000 Hz.

<div class="bg-black rounded-md mb-4" id="bkmrk--3"></div>Overall, RTPMAP is an important attribute in SDP as it allows the sender and receiver to negotiate and agree upon the codec to be used for transmitting the media.

<details id="bkmrk-all-rtpmap-codecs-pa"><summary>All RTPMAP codecs</summary>

<table class="wikitable sortable jquery-tablesorter" style="height: 6642px; width: 100%;"><thead><tr><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Payload type (PT)</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Name</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Type</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">No. of channels</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Clock rate (Hz)<sup class="reference" id="bkmrk-%5Bnote-1%5D">[\[note 1\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-1)</sup></th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Frame size (byte)</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Default packet interval (ms)</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">Description</th><th class="headerSort" role="columnheader button" style="width: 11.0962%;" tabindex="0" title="Sort ascending">References</th></tr></thead><tbody><tr><td style="width: 11.0962%;">0</td><td style="width: 11.0962%;">PCMU</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.711](https://en.wikipedia.org/wiki/G.711 "G.711") PCM [μ-Law](https://en.wikipedia.org/wiki/%CE%9C-Law "Μ-Law") audio 64 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">reserved (previously [FS-1016](https://en.wikipedia.org/wiki/FS-1016 "FS-1016") [CELP](https://en.wikipedia.org/wiki/CELP "CELP"))</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">reserved, previously [FS-1016](https://en.wikipedia.org/wiki/FS-1016 "FS-1016") [CELP](https://en.wikipedia.org/wiki/CELP "CELP") audio 4.8 kbit/s</td><td style="width: 11.0962%;">RFC 3551, previously RFC 1890</td></tr><tr><td style="width: 11.0962%;">2</td><td style="width: 11.0962%;">reserved (previously G721 or G726-32)</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">reserved, previously ITU-T [G.721](https://en.wikipedia.org/wiki/G.721 "G.721") [ADPCM](https://en.wikipedia.org/wiki/ADPCM "ADPCM") audio 32 kbit/s or ITU-T [G.726](https://en.wikipedia.org/wiki/G.726 "G.726") audio 32 kbit/s</td><td style="width: 11.0962%;">RFC 3551, previously RFC 1890</td></tr><tr><td style="width: 11.0962%;">3</td><td style="width: 11.0962%;">GSM</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">European [GSM Full Rate](https://en.wikipedia.org/wiki/GSM-FR "GSM-FR") audio 13 kbit/s (GSM 06.10)</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">4</td><td style="width: 11.0962%;">G723</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">30</td><td style="width: 11.0962%;">30</td><td style="width: 11.0962%;">ITU-T [G.723.1](https://en.wikipedia.org/wiki/G.723.1 "G.723.1") audio</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">5</td><td style="width: 11.0962%;">DVI4</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[IMA](https://en.wikipedia.org/wiki/Interactive_Multimedia_Association "Interactive Multimedia Association") [ADPCM](https://en.wikipedia.org/wiki/ADPCM "ADPCM") audio 32 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">6</td><td style="width: 11.0962%;">DVI4</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">16000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[IMA](https://en.wikipedia.org/wiki/Interactive_Multimedia_Association "Interactive Multimedia Association") [ADPCM](https://en.wikipedia.org/wiki/ADPCM "ADPCM") audio 64 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">7</td><td style="width: 11.0962%;">LPC</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">Experimental [Linear Predictive Coding](https://en.wikipedia.org/wiki/Linear_predictive_coding "Linear predictive coding") audio 5.6 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">8</td><td style="width: 11.0962%;">PCMA</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T G.711 PCM [A-Law](https://en.wikipedia.org/wiki/A-Law "A-Law") audio 64 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">9</td><td style="width: 11.0962%;">G722</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000<sup class="reference" id="bkmrk-%5Bnote-2%5D">[\[note 2\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-3)</sup></td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.722](https://en.wikipedia.org/wiki/G.722 "G.722") audio 64 kbit/s</td><td style="width: 11.0962%;">[RFC 3551 - Page 14](https://tools.ietf.org/html/rfc3551#page-14)</td></tr><tr><td style="width: 11.0962%;">10</td><td style="width: 11.0962%;">L16</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">2</td><td style="width: 11.0962%;">44100</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[Linear PCM](https://en.wikipedia.org/wiki/Linear_PCM "Linear PCM") 16-bit Stereo audio 1411.2 kbit/s,<sup class="reference" id="bkmrk-%5B2%5D">[\[2\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-4)</sup><sup class="reference" id="bkmrk-%5B3%5D">[\[3\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-5)</sup><sup class="reference" id="bkmrk-%5B4%5D">[\[4\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-6)</sup> uncompressed</td><td style="width: 11.0962%;">[RFC 3551, Page 27](https://tools.ietf.org/html/rfc3551#page-27)</td></tr><tr><td style="width: 11.0962%;">11</td><td style="width: 11.0962%;">L16</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">44100</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[Linear PCM](https://en.wikipedia.org/wiki/Linear_PCM "Linear PCM") 16-bit audio 705.6 kbit/s, uncompressed</td><td style="width: 11.0962%;">[RFC 3551, Page 27](https://tools.ietf.org/html/rfc3551#page-27)</td></tr><tr><td style="width: 11.0962%;">12</td><td style="width: 11.0962%;">QCELP</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[Qualcomm Code Excited Linear Prediction](https://en.wikipedia.org/wiki/QCELP "QCELP")</td><td style="width: 11.0962%;">RFC 2658, [RFC 3551](https://tools.ietf.org/html/rfc3551#page-28)</td></tr><tr><td style="width: 11.0962%;">13</td><td style="width: 11.0962%;">CN</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Comfort noise](https://en.wikipedia.org/wiki/Comfort_noise "Comfort noise"). Payload type used with audio codecs that do not support comfort noise as part of the codec itself such as [G.711](https://en.wikipedia.org/wiki/G.711 "G.711"), [G.722.1](https://en.wikipedia.org/wiki/G.722.1 "G.722.1"), [G.722](https://en.wikipedia.org/wiki/G.722 "G.722"), [G.726](https://en.wikipedia.org/wiki/G.726 "G.726"), [G.727](https://en.wikipedia.org/wiki/G.727 "G.727"), [G.728](https://en.wikipedia.org/wiki/G.728 "G.728"), [GSM 06.10](https://en.wikipedia.org/wiki/GSM_06.10 "GSM 06.10"), [Siren](https://en.wikipedia.org/wiki/Siren_(codec) "Siren (codec)"), and [RTAudio](https://en.wikipedia.org/wiki/RTAudio "RTAudio").</td><td style="width: 11.0962%;">RFC 3389</td></tr><tr><td style="width: 11.0962%;">14</td><td style="width: 11.0962%;">MPA</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1, 2</td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;">8–72</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[MPEG-1](https://en.wikipedia.org/wiki/MPEG-1 "MPEG-1") or [MPEG-2](https://en.wikipedia.org/wiki/MPEG-2 "MPEG-2") audio only</td><td style="width: 11.0962%;">RFC 3551, RFC 2250</td></tr><tr><td style="width: 11.0962%;">15</td><td style="width: 11.0962%;">G728</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">2.5</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.728](https://en.wikipedia.org/wiki/G.728 "G.728") audio 16 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">16</td><td style="width: 11.0962%;">DVI4</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">11025</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[IMA](https://en.wikipedia.org/wiki/Interactive_Multimedia_Association "Interactive Multimedia Association") [ADPCM](https://en.wikipedia.org/wiki/ADPCM "ADPCM") audio 44.1 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">17</td><td style="width: 11.0962%;">DVI4</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">22050</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">IMA ADPCM audio 88.2 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">18</td><td style="width: 11.0962%;">G729</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">10</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.729](https://en.wikipedia.org/wiki/G.729 "G.729") and G.729a audio 8 kbit/s; Annex B is implied unless the `annexb=no` parameter is used</td><td style="width: 11.0962%;">[RFC 3551, Page 20](https://tools.ietf.org/html/rfc3551#page-20), [RFC 3555, Page 15](https://tools.ietf.org/html/rfc3555#page-15)</td></tr><tr><td style="width: 11.0962%;">19</td><td style="width: 11.0962%;">reserved (previously CN)</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">reserved, previously [comfort noise](https://en.wikipedia.org/wiki/Comfort_noise "Comfort noise")</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">25</td><td style="width: 11.0962%;">CELLB</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Sun](https://en.wikipedia.org/wiki/Sun_Microsystems "Sun Microsystems") CellB video<sup class="reference" id="bkmrk-%5B5%5D">[\[5\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-7)</sup></td><td style="width: 11.0962%;">RFC 2029</td></tr><tr><td style="width: 11.0962%;">26</td><td style="width: 11.0962%;">JPEG</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[JPEG](https://en.wikipedia.org/wiki/JPEG "JPEG") video</td><td style="width: 11.0962%;">RFC 2435</td></tr><tr><td style="width: 11.0962%;">28</td><td style="width: 11.0962%;">nv</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Xerox PARC](https://en.wikipedia.org/wiki/Xerox_PARC "Xerox PARC")'s Network Video (nv)<sup class="reference" id="bkmrk-%5B6%5D">[\[6\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-8)</sup><sup class="reference" id="bkmrk-%5B7%5D">[\[7\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-9)</sup></td><td style="width: 11.0962%;">[RFC 3551, Page 32](https://tools.ietf.org/html/rfc3551#page-32)</td></tr><tr><td style="width: 11.0962%;">31</td><td style="width: 11.0962%;">H261</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [H.261](https://en.wikipedia.org/wiki/H.261 "H.261") video</td><td style="width: 11.0962%;">RFC 4587</td></tr><tr><td style="width: 11.0962%;">32</td><td style="width: 11.0962%;">MPV</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">MPEG-1 and MPEG-2 video</td><td style="width: 11.0962%;">RFC 2250</td></tr><tr><td style="width: 11.0962%;">33</td><td style="width: 11.0962%;">MP2T</td><td style="width: 11.0962%;">audio/video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">MPEG-2 [transport stream](https://en.wikipedia.org/wiki/MPEG_transport_stream "MPEG transport stream")</td><td style="width: 11.0962%;">RFC 2250</td></tr><tr><td style="width: 11.0962%;">34</td><td style="width: 11.0962%;">H263</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[H.263](https://en.wikipedia.org/wiki/H.263 "H.263") video, first version (1996)</td><td style="width: 11.0962%;">RFC 3551, RFC 2190</td></tr><tr><td style="width: 11.0962%;">72–76</td><td style="width: 11.0962%;">reserved</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">reserved because RTCP packet types 200–204 would otherwise be indistinguishable from RTP payload types 72–76 with the marker bit set</td><td style="width: 11.0962%;">RFC 3550, RFC 3551</td></tr><tr><td style="width: 11.0962%;">77–95</td><td style="width: 11.0962%;">unassigned</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">note that RTCP packet type 207 (XR, Extended Reports) would be indistinguishable from RTP payload types 79 with the marker bit set</td><td style="width: 11.0962%;">RFC 3551, RFC 3611</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">H263-1998</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[H.263](https://en.wikipedia.org/wiki/H.263 "H.263") video, second version (1998)</td><td style="width: 11.0962%;">RFC 3551, RFC 4629, RFC 2190</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">H263-2000</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[H.263](https://en.wikipedia.org/wiki/H.263 "H.263") video, third version (2000)</td><td style="width: 11.0962%;">RFC 4629</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">H264 AVC</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[H.264](https://en.wikipedia.org/wiki/H.264 "H.264") video (MPEG-4 Part 10)</td><td style="width: 11.0962%;">RFC 6184, previously RFC 3984</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">H264 SVC</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[H.264](https://en.wikipedia.org/wiki/H.264 "H.264") video</td><td style="width: 11.0962%;">RFC 6190</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">H265</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[H.265](https://en.wikipedia.org/wiki/H.265 "H.265") video (HEVC)</td><td style="width: 11.0962%;">RFC 7798</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">theora</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Theora](https://en.wikipedia.org/wiki/Theora "Theora") video</td><td style="width: 11.0962%;">[draft-barbato-avt-rtp-theora](https://tools.ietf.org/html/draft-barbato-avt-rtp-theora)</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">iLBC</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">20, 30</td><td style="width: 11.0962%;">20, 30</td><td style="width: 11.0962%;">[Internet low Bitrate Codec](https://en.wikipedia.org/wiki/ILBC "ILBC") 13.33 or 15.2 kbit/s</td><td style="width: 11.0962%;">RFC 3952</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">PCMA-WB</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">16000</td><td style="width: 11.0962%;">5</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [G.711.1](https://en.wikipedia.org/wiki/G.711 "G.711") A-law</td><td style="width: 11.0962%;">RFC 5391</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">PCMU-WB</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">16000</td><td style="width: 11.0962%;">5</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [G.711.1](https://en.wikipedia.org/wiki/G.711 "G.711") μ-law</td><td style="width: 11.0962%;">RFC 5391</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G718</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">32000 (placeholder)</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [G.718](https://en.wikipedia.org/wiki/G.718 "G.718")</td><td style="width: 11.0962%;">[draft-ietf-payload-rtp-g718](https://tools.ietf.org/html/draft-ietf-payload-rtp-g718)</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G719</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">48000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [G.719](https://en.wikipedia.org/wiki/G.719 "G.719")</td><td style="width: 11.0962%;">RFC 5404</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G7221</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">16000, 32000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [G.722.1](https://en.wikipedia.org/wiki/G.722.1 "G.722.1") and G.722.1 Annex C</td><td style="width: 11.0962%;">RFC 5577</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G726-16</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.726](https://en.wikipedia.org/wiki/G.726 "G.726") audio 16 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G726-24</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T G.726 audio 24 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G726-32</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T G.726 audio 32 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G726-40</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T G.726 audio 40 kbit/s</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G729D</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">10</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.729](https://en.wikipedia.org/wiki/G.729 "G.729") Annex D</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G729E</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">10</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [G.729](https://en.wikipedia.org/wiki/G.729 "G.729") Annex E</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">G7291</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">16000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [G.729.1](https://en.wikipedia.org/wiki/G.729.1 "G.729.1")</td><td style="width: 11.0962%;">RFC 4749</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">GSM-EFR</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">ITU-T [GSM-EFR](https://en.wikipedia.org/wiki/GSM-EFR "GSM-EFR") (GSM 06.60)</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">GSM-HR-08</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">ITU-T [GSM-HR](https://en.wikipedia.org/wiki/Half_Rate "Half Rate") (GSM 06.20)</td><td style="width: 11.0962%;">RFC 5993</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">AMR</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Adaptive Multi-Rate](https://en.wikipedia.org/wiki/Adaptive_Multi-Rate "Adaptive Multi-Rate") audio</td><td style="width: 11.0962%;">RFC 4867</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">AMR-WB</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">16000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Adaptive Multi-Rate Wideband](https://en.wikipedia.org/wiki/AMR-WB "AMR-WB") audio (ITU-T G.722.2)</td><td style="width: 11.0962%;">RFC 4867</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">AMR-WB+</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1, 2 or omit</td><td style="width: 11.0962%;">72000</td><td style="width: 11.0962%;">13.3–40</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Extended Adaptive Multi Rate – WideBand](https://en.wikipedia.org/wiki/AMR-WB%2B "AMR-WB+") audio</td><td style="width: 11.0962%;">RFC 4352</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">vorbis</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Vorbis](https://en.wikipedia.org/wiki/Vorbis "Vorbis") audio</td><td style="width: 11.0962%;">RFC 5215</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">opus</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1, 2</td><td style="width: 11.0962%;">48000<sup class="reference" id="bkmrk-%5Bnote-3%5D">[\[note 3\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-10)</sup></td><td style="width: 11.0962%;">2.5–60</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[Opus](https://en.wikipedia.org/wiki/Opus_(audio_format) "Opus (audio format)") audio</td><td style="width: 11.0962%;">RFC 7587</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">speex</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1</td><td style="width: 11.0962%;">8000, 16000, 32000</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Speex](https://en.wikipedia.org/wiki/Speex "Speex") audio</td><td style="width: 11.0962%;">RFC 5574</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">mpa-robust</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">1, 2</td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;">24–72</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">Loss-Tolerant [MP3](https://en.wikipedia.org/wiki/MP3 "MP3") audio</td><td style="width: 11.0962%;">RFC 5219 (previously RFC 3119)</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">MP4A-LATM</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000 or others</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[MPEG-4 Audio](https://en.wikipedia.org/wiki/MPEG-4_Audio "MPEG-4 Audio") (includes [AAC](https://en.wikipedia.org/wiki/Advanced_Audio_Coding "Advanced Audio Coding"))</td><td style="width: 11.0962%;">RFC 6416 (previously RFC 3016)</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">MP4V-ES</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000 or others</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[MPEG-4 Visual](https://en.wikipedia.org/wiki/MPEG-4_Visual "MPEG-4 Visual")</td><td style="width: 11.0962%;">RFC 6416 (previously RFC 3016)</td></tr><tr><td style="width: 11.0962%;">dynamic (or profile)</td><td style="width: 11.0962%;">mpeg4-generic</td><td style="width: 11.0962%;">audio/video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000 or other</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[MPEG-4](https://en.wikipedia.org/wiki/MPEG-4 "MPEG-4") Elementary Streams</td><td style="width: 11.0962%;">RFC 3640</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">VP8</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[VP8](https://en.wikipedia.org/wiki/VP8 "VP8") video</td><td style="width: 11.0962%;">RFC 7741</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">VP9</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[VP9](https://en.wikipedia.org/wiki/VP9 "VP9") video</td><td style="width: 11.0962%;">[draft-ietf-payload-vp9](https://tools.ietf.org/html/draft-ietf-payload-vp9)</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">L8</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[Linear PCM](https://en.wikipedia.org/wiki/Linear_PCM "Linear PCM") 8-bit audio with 128 offset</td><td style="width: 11.0962%;">RFC 3551 Section 4.5.10 and Table 5</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">DAT12</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20 (by analogy with L16)</td><td style="width: 11.0962%;">IEC 61119 12-bit nonlinear audio</td><td style="width: 11.0962%;">RFC 3190 Section 3</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">L16</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20</td><td style="width: 11.0962%;">[Linear PCM](https://en.wikipedia.org/wiki/Linear_PCM "Linear PCM") 16-bit audio</td><td style="width: 11.0962%;">RFC 3551 Section 4.5.11, RFC 2586</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">L20</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20 (by analogy with L16)</td><td style="width: 11.0962%;">[Linear PCM](https://en.wikipedia.org/wiki/Linear_PCM "Linear PCM") 20-bit audio</td><td style="width: 11.0962%;">RFC 3190 Section 4</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">L24</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">any</td><td style="width: 11.0962%;">20 (by analogy with L16)</td><td style="width: 11.0962%;">[Linear PCM](https://en.wikipedia.org/wiki/Linear_PCM "Linear PCM") 24-bit audio</td><td style="width: 11.0962%;">RFC 3190 Section 4</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">raw</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">Uncompressed Video</td><td style="width: 11.0962%;">RFC 4175</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">ac3</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">32000, 44100, 48000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Dolby AC-3](https://en.wikipedia.org/wiki/Dolby_AC-3 "Dolby AC-3") audio</td><td style="width: 11.0962%;">RFC 4184</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">eac3</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;">32000, 44100, 48000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Enhanced AC-3](https://en.wikipedia.org/wiki/Dolby_Digital_Plus "Dolby Digital Plus") audio</td><td style="width: 11.0962%;">RFC 4598</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">t140</td><td style="width: 11.0962%;">text</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">1000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[Text over IP](https://en.wikipedia.org/wiki/Text_over_IP "Text over IP")</td><td style="width: 11.0962%;">RFC 4103</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">EVRC  
EVRC0  
EVRC1</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[EVRC](https://en.wikipedia.org/wiki/Enhanced_Variable_Rate_Codec "Enhanced Variable Rate Codec") audio</td><td style="width: 11.0962%;">RFC 4788</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">EVRCB  
EVRCB0  
EVRCB1</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">8000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[EVRC-B](https://en.wikipedia.org/wiki/Enhanced_Variable_Rate_Codec_B "Enhanced Variable Rate Codec B") audio</td><td style="width: 11.0962%;">RFC 4788</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">EVRCWB  
EVRCWB0  
EVRCWB1</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">16000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[EVRC-WB](https://en.wikipedia.org/wiki/Enhanced_Variable_Rate_Codec_B "Enhanced Variable Rate Codec B") audio</td><td style="width: 11.0962%;">RFC 5188</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">jpeg2000</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[JPEG 2000](https://en.wikipedia.org/wiki/JPEG_2000 "JPEG 2000") video</td><td style="width: 11.0962%;">RFC 5371</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">UEMCLIP</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">8000, 16000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[UEMCLIP](https://en.wikipedia.org/w/index.php?title=UEMCLIP&action=edit&redlink=1 "UEMCLIP (page does not exist)") audio</td><td style="width: 11.0962%;">RFC 5686</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">ATRAC3</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">44100</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[ATRAC](https://en.wikipedia.org/wiki/Adaptive_Transform_Acoustic_Coding "Adaptive Transform Acoustic Coding")3 audio</td><td style="width: 11.0962%;">RFC 5584</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">ATRAC-X</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">44100, 48000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[ATRAC](https://en.wikipedia.org/wiki/Adaptive_Transform_Acoustic_Coding "Adaptive Transform Acoustic Coding")3+ audio</td><td style="width: 11.0962%;">RFC 5584</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">ATRAC-ADVANCED-LOSSLESS</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">(various)</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[ATRAC](https://en.wikipedia.org/wiki/Adaptive_Transform_Acoustic_Coding "Adaptive Transform Acoustic Coding") Advanced Lossless audio</td><td style="width: 11.0962%;">RFC 5584</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">DV</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[DV](https://en.wikipedia.org/wiki/DV "DV") video</td><td style="width: 11.0962%;">RFC 6469 (previously RFC 3189)</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">BT656</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[ITU-R BT.656](https://en.wikipedia.org/wiki/ITU-R_BT.656 "ITU-R BT.656") video</td><td style="width: 11.0962%;">RFC 3555</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">BMPEG</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">Bundled MPEG-2 video</td><td style="width: 11.0962%;">RFC 2343</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">SMPTE292M</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[SMPTE 292M](https://en.wikipedia.org/wiki/SMPTE_292M "SMPTE 292M") video</td><td style="width: 11.0962%;">RFC 3497</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">RED</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">Redundant Audio Data</td><td style="width: 11.0962%;">RFC 2198</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">VDVI</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">Variable-rate DVI4 audio</td><td style="width: 11.0962%;">RFC 3551</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">MP1S</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">MPEG-1 Systems Streams video</td><td style="width: 11.0962%;">RFC 2250</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">MP2P</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">MPEG-2 Program Streams video</td><td style="width: 11.0962%;">RFC 2250</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">tone</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">8000 (default)</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">tone</td><td style="width: 11.0962%;">RFC 4733</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">telephone-event</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">8000 (default)</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[DTMF](https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling "Dual-tone multi-frequency signaling") tone</td><td style="width: 11.0962%;">RFC 4733</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">aptx</td><td style="width: 11.0962%;">audio</td><td style="width: 11.0962%;">2 – 6</td><td style="width: 11.0962%;">(equal to sampling rate)</td><td style="width: 11.0962%;">4000 ÷ sample rate</td><td style="width: 11.0962%;">4<sup class="reference" id="bkmrk-%5Bnote-4%5D">[\[note 4\]](https://en.wikipedia.org/wiki/RTP_payload_formats#cite_note-11)</sup></td><td style="width: 11.0962%;">[aptX](https://en.wikipedia.org/wiki/AptX "AptX") audio</td><td style="width: 11.0962%;">RFC 7310</td></tr><tr><td style="width: 11.0962%;">dynamic</td><td style="width: 11.0962%;">jxsv</td><td style="width: 11.0962%;">video</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">90000</td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;"> </td><td style="width: 11.0962%;">[JPEG XS](https://en.wikipedia.org/wiki/JPEG_XS "JPEG XS") video</td><td style="width: 11.0962%;">RFC 9134</td></tr></tbody></table>

</details>##### FMTP

The "fmtp" (format parameters) attribute in SDP (Session Description Protocol) is used to describe the format parameters of a media stream, specifically for codecs that support dynamic negotiation of parameters. It specifies the media format parameters as a set of parameter name-value pairs, separated by semicolons.

The format of the "fmtp" attribute is as follows:

```
a=fmtp:<format> <parameter_name>=<value>;<parameter_name>=<value>;...
```

<div class="bg-black rounded-md mb-4" id="bkmrk--4"></div>- `<format>`: specifies the media format to which the parameters apply.
- `<parameter_name>`: specifies the name of the parameter.
- `<value>`: specifies the value of the parameter.

For example, the "fmtp" attribute for the H.264 video codec may look like:

<div class="bg-black rounded-md mb-4" id="bkmrk--5"></div>```
a=fmtp:120 profile-level-id=42801E; packetization-mode=1; sprop-parameter-sets=Z0IACpZTBYmI,aMljiA==
```

In this example, the `<format>` value is 120 (which is the format number for H.264). The `<parameter_name>` values include "profile-level-id", "packetization-mode", and "sprop-parameter-sets", and their corresponding `<value>`s are "42801E", "1", and "Z0IACpZTBYmI,aMljiA==", respectively. These parameters provide information such as the profile and level of the codec, the packetization mode, and the parameter sets required for decoding the video stream.

The "fmtp" attribute is typically used in conjunction with the "rtpmap" attribute to describe media formats that use RTP (Real-time Transport Protocol) for transmission.

This is a SIP response to an INVITE request shown above. It has a status code of 200 OK, indicating that the request was successful. The Via header indicates the path that the request followed. The To header contains the tag that identifies the current dialog. The From header contains the tag that identifies the previous dialog. The Call-ID header is used to identify the call. The CSeq header contains the sequence number and method of the request. The Contact header specifies the address where the response should be sent. The Content-Type header indicates that the body of the message is in SDP format. The SDP message body includes connection information, timing information, and media information for both audio and video. In this response, some codecs have been removed from both audio and video streams.

```
SIP/2.0 200 OK
Via: SIP/2.0/UDP pc33.atlanta.com;branch=z9hG4bK776asdhds
To: Bob <sip:bob@biloxi.com>;tag=2482893830n
From: Alice <sip:alice@atlanta.com>;tag=1928301774
Call-ID: a84b4c76e66710
CSeq: 314159 INVITE
Contact: <sip:bob@192.0.2.4:5060>
Content-Type: application/sdp
Content-Length: 204

v=0
o=- 123456 789012 IN IP4 192.0.2.4
s=SIP Call
c=IN IP4 192.0.2.1
t=0 0
m=audio 49170 RTP/AVP 0 18
a=rtpmap:0 PCMU/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
m=video 49172 RTP/AVP 31
a=rtpmap:31 H261/90000

```

- `v=0`: The protocol version being used is 0.
- `o=- 123456 789012 IN IP4 pc33.atlanta.com`: This is the origin field. The `-` indicates that the session is not valid for further communication. `123456` is the session ID, which is chosen arbitrarily. `789012` is the session version number. `IN` stands for "Internet", and `IP4 pc33.atlanta.com` (192.0.2.4) is the address of the host that originated the session.
- `s=SIP Call`: The session name, which is an optional field. In this case, it is "SIP Call".
- `c=IN IP4 192.0.2.1`: The connection information for the session. This field specifies the network type, address type, and address information. In this case, it indicates that the session is using the Internet network, IPv4 address, and the address is `192.0.2.1`.
- `t=0 0`: The timing information for the session. The first `0` indicates the start time of the session, which is "now". The second `0` indicates the session will not terminate automatically.
- `m=audio 49170 RTP/AVP 0 18`: This is the media description for the audio stream. `audio` indicates that this is an audio stream. `49170` is the port number being used for the RTP stream. `RTP/AVP` specifies the protocol being used (RTP) and the payload format for the audio data (AVP). `0` and `18` are the RTP payload types being used for this stream.
- `a=rtpmap:0 PCMU/8000`: This attribute maps the payload type `0` to the audio codec PCMU and indicates that the audio is sampled at a rate of 8000 Hz.
- `a=rtpmap:18 G729/8000`: This attribute maps the payload type `18` to the audio codec G.729 and indicates that the audio is sampled at a rate of 8000 Hz.
- `a=fmtp:18 annexb=no`: This is an optional attribute that provides additional parameters for the G.729 codec. In this case, it specifies that the codec is not using the Annex B format.
- `m=video 49172 RTP/AVP 31`: This is the media description for the video stream. `video` indicates that this is a video stream. `49172` is the port number being used for the RTP stream. `RTP/AVP` specifies the protocol being used (RTP) and the payload format for the video data (AVP). `31` is the RTP payload type being used for this stream.
- `a=rtpmap:31 H261/90000`: This attribute maps the payload type `31` to the video codec H.261 and indicates that the video is sampled at a rate of 90000 Hz.

#### Multiple M Lines

In SIP SDP, multiple "m=" lines can be included in a single SDP message to provide information about multiple media streams within a session. Each "m=" line corresponds to a different type of media, such as audio, video, or data. The "m=" line specifies the transport protocol and port number to be used for that particular media stream, as well as the format of the media data being transmitted. Each "m=" line can also have its own set of media-level attributes, such as the RTP payload types being used for different codecs, or the clock rate of the media data. By including multiple "m=" lines in a single SDP message, a SIP session can support multiple media streams simultaneously.

![image.png](https://wiki.tinod.net/uploads/images/gallery/2023-05/scaled-1680-/heVX1864a2dDMvTd-image.png)