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

[Eric Reichert]

On 9/16/16, 4:22 PM, "Libav-user on behalf of Andy Shaules" <libav-user-bounces at ffmpeg.org on behalf of bowljoman at gmail.com> wrote:

    On 9/16/2016 6:06 AM, Eric Reichert wrote:
    > On 9/16/16, 8:30 AM, "Libav-user on behalf of Carl Eugen Hoyos" <libav-user-bounces at ffmpeg.org on behalf of ceffmpeg at gmail.com> wrote:
    >
    >      2016-09-16 14:24 GMT+02:00 Eric Reichert <ereichert at trafficland.com>:
    >      
    >      > The streams I’m working with are of the Annex B variety.
    >      
    >      I would have expected that the rtp specification for H.264
    >      requires the video stream not to be in this format, am I
    >      wrong?
    >      
    >      Can you provide such a stream (or even better a patch
    >      to FFmpeg that allows to create a stream so a possible
    >      fix can be tested)?
    >      
    >      Carl Eugen
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    >
    > RFC 3984/6184 do not prescribe Annex B.  The old version of our software has to convert the 3984/6184 formatted H.264 into the Annex B format in order for (the ancient version of) FFMPEG to decode the video.  That is, the old version of our software parses the RTP, reassembles the NAL Units from the fragmentation units, and adds the start codes before submitting the NAL units to the decoder.
    >
    > Does that answer your question?  It could be that I don’t understand the question or the specs well enough.
    >
    > As far as providing a stream, I can provide tons of network captures carrying streams of that type.  How shall I get them to you?
    >
    > Regarding a patch, it would be months before I could get anything submitted.  My C skills aren’t great and I don’t know the FFMPEG codebase that well.
    >
    > By the way, thanks for the help and your continued work.  You’ve got a tough job answering all the questions.
    >
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    Why dont you just add a packet type 96 to the sdp file? forming the 
    sprop-parameter-sets is not too difficult.
    
    you could also optionally use a third party lib for networking and do 
    the demux yourself and just use av_codec for decoding.
    
    
    Andy
    
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Andy: 

I don’t think you understand the problem.

First, of course we can use SDP files.  I was trying to point out that it may be possible to auto-detect the streams without an SDP file.

Second, one of the main reasons we’re rewriting our application is that we don’t want to do the demuxing ourselves.  We’ve already been down that road.