[Vorbis] Encoding multiple tiny audio files

[andy]

The difference is most likely coming from the psychoacoustic model and
with it not having time to properly adapt to the signal within such
short periods of time.. At the start it's got to assume a fairly worst
case of silence having been playing before the sound, and so the
psychoacoustic model hasn't had time to adapt yet..

I'd be tempted to try a slightly lower quality setting, it's likely
that because the psychoacoustics aren't having time to adapt with such
short files that it's possibly over-encoding the audio files for a
given quality due to their short durations..

Or possibly windowing related due to the shortness of the files ?

On Mon, Mar 30, 2009 at 9:52 AM, Michał Czuczman
<mczuczman at ivosoftware.com> wrote:
> Hi all,
>
> I want to make a static database containing hundreds of thousands of very
> short audio files, each having not more than 100 milliseconds. These are made
> by splitting larger audio files into tiny pieces.
>
> I encode all the little files separately, but do not store 3 vorbis header
> packets, which are the same for all the files. I do not use ogg stream, only
> store plain vorbis packets.
>
> When I encode the longer files, which altogether have the same audio length,
> I get 20% higher compression ratio. However, in order to have fast lookup
> times, I cannot deal with decoding such large files, only to get a little
> chunk in them.
>
> Do you know of a way to compress the little chunks, but achieve compression
> ratio of those primary audio files? Where does the difference in compression
> rate come from?
>
> Is it possible to get even higher compression rates without quality loss,
> by tweaking any parameters or blocksizes hardcoded in libvorbis source?
>
> Thanks,
>
> Michał
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