[Icecast] Accumulating latency in nsv stream

msg msgi at cybertheque.org
Mon Sep 26 19:33:53 UTC 2005


We have a problem with accumulating latency in a 1 fps nsv video
stream; the delay is about 5 sec. when the stream is first mounted
but after about 10 hours it is up to 1/2 hour and after 24 hours
it is almost an hour (no frames are dropped, a client viewing the
stream just sees video delayed by those amounts).

I have commented-out the <burst-on-connect> and <burst-size> tags
in icecast.xml without any difference in the symptoms.

The configuration:

icecast 2.2.0 on Linux 2.4.27
nsvcap (nsvenc doesn't support the video driver properly) sourcing
   on Win2kServerSp3/PIII-500/384M/Bt848-btwincap:
      VP3 codec configured for est 15kbps/7kbps key, 1fps output,
      1fps capture, 6 -> 11kbps actual bitrate, no audio;
      nsvcap reports d=107 vinq=0 ainq=0 (0 dropped) after 10 hours.

I've seen mentioned that frame rates should be in multiples of two
with key frame rates evenly divisible, but I am after the lowest
possible rate which seems to be 1 fps even though the input frame
rate can be set to fractions of 1 fps.

All help is much appreciated.

Michael Grigoni
Cybertheque Museum

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