[vorbis] Ogg streaming on low bandwidth

[Jonathan]

A very interesting note on this:

Garf, the creator of the Garf Tuned libraries, also did some work on what he
calls "floggy" Vorbis, which has bitrates of around 4kbps (you can check out
some samples at sjeng.org).  If you must push bitrate very low, try using an
encoder compiled with the GT3b1 libraries, as "floggy" mode is included.  He
also mentioned that the quality at such low bitrates could be greatly
improved by applying a 70Hz highpass to the file before encoding.  In fact,
the next version of the GT library will have an automatic highpass at very
low bitrates.  You can also resample down to 6kHz sampling rate in Oggenc,
if you'd like to push bitrate even lower, though I don't know if that would
be too low.

Hope this helps. =)

-Jonathan

Stan Seibert wrote:
> On Thu, 2003-08-14 at 00:50, engdev wrote:
>> Was wondering if any gurus could tell me if it is
>> possible to stream Ogg on very low bandwidth links (for
>> example satellite phone) where
>> the expected bandwidth would almost certainly be less
>> than 19Kbps, and probably more like 10Kbps.
>
> For testing how low Vorbis can go, you don't need a full
> client/server setup at first.  I did some fiddling using
> sox and oggenc (command line tools often found on Linux
> systems, but available for windows as well). You could
> also use an audio editor that lets you resample audio and
> mix down a stereo file to mono along with OggdropXP to do
> the Vorbis encoding.
>
> I took a track I had ripped from CD and used sox to
> resample and mix it down to 8 kHz mono:
>
> sox test.wav -r 8000 -c 1 test8kHz.wav resample
>
>  I then encoded it using quality -1, the lowest VBR
> quality setting the current encoder allows:
>
> oggenc -q -1 test8khz.wav
>
> The resulting file was 10.9 kbps, but without any bitrate
> management, so there were bitrate spikes that might not
> be good for your application. The result was bad but
> livable, though I've never heard MP3 at this low of a
> bitrate, so I have no point of reference.
>
> Harder limits can be achieved with managed bitrates.
> With:
>
> oggenc --managed -M 10 test8khz.wav
>
> I got a file with the bitrate capped at 10 kbps (but no
> explicit minimum or average requested).  Not
> surprisingly, the encoder used every bit possible under
> these constraints, resulting in a file with an average
> bitrate of 10 kbps.  In comparing the VBR with the
> managed bitrate version, you can definitely hear the
> points where the encoder jumped the bitrate up in the
> quality -1 encoding to prevent a particularly bad
> artifact, but the managed bitrate version had to let
> through.
>
> Incidentally, I found that an average bitrate of 8.3 kbps
> was the lowest I was able to push the encoder to:
>
> oggenc --managed -b 8 test8khz.wav
>
> (That sets the average bitrate but not the min or max)
>
> Anything lower and oggenc informed me that the bitrate
> parameters were invalid.
>
> ---
> Stan Seibert
>
>
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