[icecast] streaming silence to Winamp
msmith at xiph.org
Tue Aug 5 01:06:08 UTC 2003
On Tuesday 05 August 2003 05:56, James Ponder wrote:
> I have just integrated libshout2 and libvorbisenc into mserv, my music
> server (www.mserv.org).
> It all works well. Thanks for a great product.
> The problem I have is that when there is a pause between songs of around 10
> seconds, Winamp (2.91) decides (due to the 64kbps dropping to a 2kbps
> stream I guess), that it needs to re-buffer. It fails miserably and
> generally dumps the connection, or at the very least a 10 second pause
> turns in to a 20 second pause (10 seconds re-buffering and then the 10
> second pause I wanted in the first place).
> I'm not sure where the problem lies exactly, but I suspect it's just
> Winamp's poor re-buffer algorithm.
Not really - it's not a winamp-specific problem, most of the audio players do
it the same way, and it's not entirely unreasonable.
> This sounds like a problem that may have been solved before - how do I
> ensure that for long periods (minutes) that both Icecast and Winamp are
> Best wishes, James
The problem is, as you've guessed, that the bitrate drops to something very
low (probably actually less than 2 kbps), but this causes problems given the
way libogg by default frames vorbis encoded data. Ogg pages are generally
generated at about 4 kB in size - at 2 kbps, this is 16 seconds of audio.
This means that _no_ data is sent at all for ~16 seconds. So, the trick is to
flush the ogg stream (forcing a shorter-than-normal page to be created) if
the bitrate has dropped too low. ices2 does this by forcing a new page if the
current page contains more than ~2 seconds of audio (or some number - I think
it's 2 seconds).
To do this, you should (conditionally, based on current page length) call
ogg_stream_flush() instead of ogg_stream_pageout() - see ices/src/encode.c,
around line 220, for an example of doing this (ices2 does not currently
_accurately_ calculate the current page length, it uses an approximation
which could sometimes be a fair way off - I should change this).
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