[vlc-devel] Feature request: Support for sending in-band PPS/SPS information when doing RTP streaming of H264 videos in raw mode
romixlev at web.de
Thu Nov 29 09:36:25 CET 2012
I'm using libVLC (latest version) as part of a bigger solution to
stream videos in H264 format over RTP using raw mode, i.e. no mux is
set explicitly. The original video file is not in H264 format,
therefore VLC first does some transcoding into H264 and then the usual
streaming of the transcoding result over RTP.
Since I use libVLC as part of a setup used for a video-conferencing
solution, I have to stream over RTP with SPS/PPS information sent
in-band. I asked my colleagues why there is such a specific
requirement for in-band and I was told that this is according to the
IETF guidelines/recommendations for video-conferencing. And BTW, all
SIP-related handling in our system happens higher in the stack and
libVLC is only supposed to transcode and stream.
But unfortunately VLC seems to support only SPS/PPS settings that are
communicated over SDP descriptions, when it streams H264 over RTP.
Even if the incoming data for the RTP streamer contain this SPS/PPS
information, VLC seems to remove it from the stream and then put it
into a newly created SDP. Afterwards it streams the video without
putting SPS/PPS before each I-frame. (At the same time it is
interesting to observe that VLC when used as a client expects in-band
SPS/PPS in the incoming RTP stream ;-)
I did some research on forums and VLC mailing lists and found out that
VLC used to support sending SPS and PPS in-band before 2010. But later
this support was removed for some reason (why?). More over, it is not
even possible to enable/disable it using a command-line option.
After I realized the current situation with SPS/PPS support in VLC, I
asked about it on the IRC chat. I was lucky enough to meet there one
of the x264 developers (don't remember his name). He told me that it
should be fairly easy to add support for sending SPS/PPS in-band, as
the old code for doing is still around and just needs to be
uncommented or something like this. He mentioned that only a few lines
should be changed in the code. Is it really the case? Can someone fix
I tried to file an issue at the official bug tracker:
https://trac.videolan.org/vlc/newticket But apparently it does not
work. You cannot register any new accounts, because this system always
tells you "Environment not found" :-(
Therefore, I post on this mailing list to make VLC developers aware of
the SPS/PPS problem I have.
I'd like to ask you for two things:
1) It would be useful if this issue could be filed in the issue
tracker by someone who already has an account. May be this issue
tracker will work in this case? Even better would be to fix the issue
2) If this SPS/PPS-related issue is really so easy to fix as mentioned
on the IRC chat, it would be nice if someone could quickly fix it.
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