[FFmpeg-devel] How to implement pcap ffmpeg format?

[Zhao Zhili]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of sonntex
> Sent: 2023年2月22日 21:59
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Subject: Re: [FFmpeg-devel] How to implement pcap ffmpeg format?
> 
> So, if I have an rtp stream inside my application and want to save it
> somehow to a playable media container, I have to wrap this stream to
> something that could be transferred by pipe to ffmpeg, for instance to ivf
> or to h264 byte stream. The first format requires deep codec parsing to

Why not remux RTP to something like TS at the first replace, instead of deal with pcap?

> extract at least width and height, perhaps other properties. Seems easy but
> non-unified. Another approach is to pass the stream to a local udp socket,
> simultaneously execute and control the ffmpeg process. It could lead to
> data loss and requires socket coding in such a simple application.
> 
> I understand why ffmpeg developers don't want to include pcap support to
> ffmpeg but it could be implemented as an external code by somebody else for
> whom it seems to be useful. I can't really find any blockers to do that
> except that all the code inside rtpdec is encapsulated in its *.c file and
> is not accessible from a hypothetical new pcap format. What I found is that
> udp.c derives url protocol interface and does the same as pcap format
> should do - extract rtp packets from a source and pass it further to
> rtpdec. The problem is that pcap format is a format, not a protocol, which
> reads data from ffmpeg file protocol. And the question was how to build the
> chain of <file protocol> -> <input pcap format> -> <input rtp format>?
> 
> On Wed, Feb 22, 2023 at 12:54 PM Rémi Denis-Courmont <remi at remlab.net>
> wrote:
> 
> > Hi,
> >
> > I agree with Kieran that this doesn't look like it belongs in FFmpeg or in
> > any media framework. In fact, Wireshark has some support for extracting
> > media from RTP, and that seems like the right place for it.
> >
> > With that said, you can't realistically pass RTP packets on the standard
> > input. RTP is datagram-based. Packet boundaries are relevant; it can't go
> > over a pipe. Unless you use a Unix datagram socket as standard input, but
> > that would be very weird.
> >
> > Besides, there may be multiple streams on different ports, with different
> > payload maps, and the receiver needs to know which port which packet came
> > on.
> >
> > Note: Unfortunately, earlier attempts to standardise a container for
> > RTP/RTCP packets have failed.
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