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

sonntex sonntex at gmail.com
Wed Feb 22 19:22:16 EET 2023


Are you sure that vp8 and vp9 can be put to mpeg-ts?

On Wed, Feb 22, 2023 at 3:25 PM Zhao Zhili <quinkblack at foxmail.com> wrote:

> > -----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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