[gst-devel] playing live mpegts stream over udp

[Edward Hervey]

On Fri, 2011-01-14 at 20:08 +0100, Julien Isorce wrote:
> Hi,
> 
> I am trying to play nicely a usual mpegts stream from network.  (720p
> h264/ac3 mpegts over udp multicast)
> The pipeline is: 
> gst-launch uridecodebin uri=239.102.101.3:1013 ! then audio and video
> renderers.
> My network interface is connected in 1GO.
> 
> With default properties, the video has a lot of macro block. If I
> record the network packets in a pcap file then 
> I can perfeclty play the stream using pcapparse.
> So I think the problem comes from some buffering pbs.
> 
> When configuring with some heuristics use-buffering=1, buffer-duration
> and buffer-size properties of uridecodebin,
> the video contains less macro blocks but it still contains enough
> block to make me fill it's not normal.
> 
> With VLC the stream is played almost perfectly.
> 
> Am I doing something wrong ? Should I need a something like a
> jitterbuffer (no rtp here) ?

  I had a look at the problem over the weekend (reproduced it by using
vlc server streaming mpeg-ts over udp) and basically the timing
algorithms in mpegtsdemux are completely bogus (which is something we
knew, but never confirmed). By introducing an evil hack in mpegtsdemux
for that specific setup I could get it to play much more smoothly.

  You also want to set the udpsrc buffer-size property to a much higher
value (500kB should do it) if you're using high-ish bandwith streams.

  The solution ?
  * Stream using proper rtsp (when vlc server is configured that way it
works flawlessly with GStreamer).
  * Fix mpegtsdemux (I'd recommend buying hospital-sized packs of
aspirin if you do that)
  * Help work on the from-scratch tsdemux project (some people looked
into a similar issue some time back)

     Edward

> 
> Any help would be appreciated.
> Sincerely
> Julien Isorce
> 
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