[vorbis] Ogg Vorbis and streaming

[gtgbr at gmx.net]

Henri Jylkka wrote:
> Hi. I'd like to ask a little about where Ogg stands today when it comes
> to streaming audio.
> 
> The VBR has been the main argument in the incompatibility for streaming
> but has this changed somehow or will it? Is there something else
> besides quick and large scaled bandwith usage variations and the
> difficulty of buffering, that could cause problems?
> 
> CBR could be used but some people say that it reduces the sound
> quality. When doing some test listnening I couldn't tell much
> differences between VBR and CBR but I might as well be half-deaf.. I'd
> like to get the most out of Ogg potential by using VBR but if it means
> problems with streaming or some listeners not being able to listen at
> all, then I will choose CBR.

My personal experience shows that streaming Vorbis is entirely
trouble-free if your target audience is people with 64-128 kbps
downstream. For example (I have an 128kbps upstream), streaming at -q
1.5 is really nice for 128kbps users. The average of the stream lies
somewhere around 88 kbps at excellent quality and plenty of overhead.
VBR is clearly not an issue there.

Streaming at -q -1 (or a higher q with downsampling) for 64kbps ISDN
users is working very good, too. It gets a little harder for lower
bitrates, as quality degration becomes more noticeable and one really
wants to shove as many bits as possible through the line - however, it's
still possible to get good results with ABR (oggenc parameter: -b
<target_bitrate> --managed --resample <target_sample_rate> [--downmix])
and no further hard bandwidth limits. (oggenc parameter: -M
<max_bitrate>)

It's mostly a matter of experimentation and finding the sweet spot for
your particular needs and audience. I recommend you try this by yourself
by either encoding some music to Vorbis at the bitrates you need, or
combine that with a real streaming experiment (which is most useful, as
you can ask some friends on modems to listen to your stream and report
problems) ... Icecast 2 will allow you to do just that.
(www.icecast.org)

<p>Moritz
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