[FFmpeg-soc] [PATCH] xiph packetizer

[Martin Storsjö]

On Thu, 29 Jul 2010, Josh Allmann wrote:

> On 29 July 2010 04:54, Martin Storsjö <martin at martin.st> wrote:
> > On Thu, 29 Jul 2010, Josh Allmann wrote:
> >
> >> > Also, there's an issue with vorbis timestamps if you stream copy from an
> >> > ogg file - not all packets have pts/dts set when reading them, and for
> >> > vorbis, you'd need to decode it to figure out the proper length of each
> >> > frame. In ffmpeg.c, lines 1622-1623, the pts is updated using an estimate
> >> > of the frame size, which doesn't turn out to be right (in my case at
> >> > least).
> >> >
> >> > If playing only vorbis over RTSP/RTP, it still worked, but the timestamps
> >> > advanced slowly from 0 to perhaps 1, then jumped to 5-6 seconds, advanced
> >> > slowly there again, and jumped onwards when the ogg demuxer returned a
> >> > packet that actually had a timestamp. Combined with a video stream, it
> >> > doesn't work too well in that setup of course.
> >> >
> >> > If live transcoding into theora/vorbis, and sending it out over RTSP/RTP,
> >> > it seemed to work really well, though!
> >> >
> >>
> >> That's pretty strange, I would like to see your sample. With Big Buck
> >> Bunny, Vorbis standalone timestamps are fairly linear.
> >
> > Can you give an url to this test clip?
> >
> 
> http://mirrorblender.top-ix.org/peach/bigbuckbunny_movies/big_buck_bunny_480p_stereo.ogg

Hmm, ffplay has some weird issues with this file on OS X, but if hacked to 
request slightly larger YUV overlay buffers from SDL (with a width being a 
multiple of 16), it works fine.

> >> Using Theora and Vorbis together with RTSP/RTP, things work well.
> >> Theora standalone is still full of artifacts around motion with TCP,
> >> and UDP is a slideshow because of all the dropped packets. Tomorrow,
> >> I'll copy over the packetization routine from Feng and see if the
> >> results are more sane.
> >
> > Hmm, that sounds really strange. Can you give the command lines that
> > you've used for these test setups?
> >
> 
> ffmpeg -re -i acodec copy -vcodec copy -f rtsp rtsp://localhost/foo.sdp
> 
> also with -an, -vn, and ?tcp variants.
> 
> ffplay rtsp://localhost/foo.sdp

Hmm, that's weird, Theora works just fine over TCP for me. Over UDP, I get 
lots of artefacts due to dropped packets, though, but that's probably to 
be expected. Tested it with the latest patch you sent (and with the 
previous one with my local modifications).

// Martin