[Libav-user] Decoding RTP streams with in-band SDP

Eric Reichert ereichert at trafficland.com
Fri Sep 16 03:12:48 EEST 2016

Is there an option that can be passed to avformat_open_input (or another call) that will enable decoding of an RTP stream carrying H.264 video with the SDP in-band without having to pass an out-of-band SDP file?

My software is connecting to multicast streams of the type I’ve described.  Neither the command line version of ffmpeg nor my software will decode the streams when I pass a URI of the format rtp://blah.  They both produce the following error.

[rtp @ 0x7f9d00000b20] Unable to receive RTP payload type 96 without an SDP file describing it

Trying to open the same streams using URI of the format udp://blah fails to detect the video correctly which is somewhat expected.

It seems to me that avformat should be able to auto detect in-band SDP and do the right thing but that doesn’t seem to be the default behavior.

I couldn’t find anything in the docs or the code that indicates there’s such an option so I’m hoping it’s in the code somewhere I’m not looking.

If it’s not possible at this time is there a reason why it shouldn’t be able to detect in band SDP?
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