[gstreamer-bugs] [Bug 606662] h264: add stream-format to output caps
bugzilla at gnome.org
Sun Jan 17 16:30:04 PST 2010
GStreamer | gst-plugins-ugly | git
--- Comment #20 from Felipe Contreras <felipe.contreras at gmail.com> 2010-01-18 00:30:02 UTC ---
(In reply to comment #19)
> (In reply to comment #18)
> > That's because ffdec_h264 is wrongly adding a parser (only on byte-stream
> > mode), see gst_ffmpegdec_open().
> "wrongly"? Not in the current way of doing things.
Yes, wrongly, because it should not be needed.
> > It is possible to generate a muxed clip that
> > contains trimmed access-units, it would play fine on totem, but not ffplay
> > (mplayer, vlc, and pretty much everything out there).
> I don't know what this means. If this means "totem plays broken files better
> than ffplay", I'm ok with that.
It means gst-ffmpeg is doing something nobody is doing. Therefore we shouldn't
rely on that behavior.
> > This is precisely the reason why rtph264dec+ffdec_h264 only works on bytestream
> > mode:
> Actually, I think it only works in bytestream mode because H.264 over RTP is
> only specified in bytestream mode. Unless there's an RFC after 3984 that I
> don't know about. It seems unlikely, though, since AVC format is fundamentally
> incapable of resynchronization after dropping packets.
RFC 3984 on section 1.1 clearly states that neither byte-stream nor avc are
Annex B of H.264 defines an encapsulation process to transmit such NAL units
over byte-stream oriented networks. In the scope of this memo, Annex B is not
This means it's up to the decoder/depayloader to agree on an interface: could
be byte-stream, could be avc, could be something custom. It doesn't matter
because the RTP stream is different anyway.
> > /* FIXME, non-bytestream handling is freaking out ffmpeg. Apparently we need to
> > * group all NAL units belonging to one frame together */
> Of course. That is how AVC format is defined.
Right, and the decoders out there assume the same for byte-stream format.
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