[Icecast-dev] Speex Support for Ices?

[Geoff Shang]

Hi,

"Burst on connect" isn't going to change the buffering.  It'll just affect 
how quickly the client starts playing.

The main buffer in question here is that on the client.  Sending a burst of 
data when the client connects will simply serve to fill the buffer up more 
quickly, which results in the player beginning to play sooner.  It won't 
reduce any latency, and if the player's buffer is smaller than the burst 
size, it would probably increase it.

In my experience, the main factors in determining latency are the size of 
the client buffer and the bit rate of the audio.  a 64k buffer will contain 
the same amount of data regardless of the bit rate, but that data will 
represent a longer period of time at lower bit rates than at higher ones.

As an example, the Shoutcast server at least used to have a fixed 1 MB 
buffer which couldn't be altered.  At 16 kbps, this buffer represented 
something like 5 minutes of audio.

The other thing to keep in mind, if low latency is important, is that vorbis 
does have some in-built latency if my memory serves me correctly.  I do know 
that speex is a lower latency codec, but I don't know how much latency the 
ogg framework might introduce, nor how much would be introduced by the TCP 
and HTTP overhead that Icecast is currently limited to.

I'm not an expert, but I'dve thought that something that is low latency 
would need to use an UDP implementation such as RTP, such as in use in VOIP 
applications.

Geoff.



----- Original Message ----- 
From: "Thomas B. Ruecker" <dm8tbr at afthd.tu-darmstadt.de>
To: <icecast-dev at xiph.org>
Sent: Tuesday, July 17, 2007 12:12 AM
Subject: Re: [Icecast-dev] Speex Support for Ices?


roger schrieb:
> Using ices w/ icecast, I noticed a 15 second delay between live audio
> and live stream.
which is probably introduced by client side buffering.
If you want to minimize buffers - you should turn of burst-on-connect in
icecast.
> Another item I recently started researching, was using speex (speex.org
> related to ogg/vorbis).   I'm wondering if this might significantly
> reduce delay times.
It might even increase lag - depending on client software
If the client software uses fixed size buffers it will buffer longer
periods.
> One question I ponder is if user's players have the speex codec compared
> to the more popular vorbis/ogg codec.
Certainly fewer players will have support for speex I guess.

If you want to experiment with speex: I think ezstream can handle this.
oggfwd too

Cheers

Thomas

PS: I think this is off-topic here. This is more of an user question
than an question about further development of icecast?

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