[Speex-dev] To CELP or not to CELP ... at higher bitrates
Jean-Marc.Valin at USherbrooke.ca
Sat Oct 29 05:55:40 PDT 2005
> My approach, therefore, is to build a Windows "wave" file asynchronously by
> using a streaming retransmission protocol to request the retransmission of
> any lost packets from a short-term history buffer maintained by each
> sender, thus "filling in any gaps" after the fact. In this way we can
> guarantee that a perfect recording will always result.
For *near*-perfect recording, record at 96 kHz/24 bps, 8 channels,
uncompressed. That'll be about 18 Mbps bitrate.
> Since the resulting recorded quality is the ONLY concern, and since we can
> stipulate that all parties will always have access to broadband-scale
> connectivity, does using a CELP-based codec such as Speex make the most
> sense in this application?
You already answered the question, haven't you? ;-)
> I would be running Speex in ultra-wideband with 32 or 48 kHz sampling and
> its bitrate completely open-ended and upwards of 44 kbps ... but higher bit
> rates (of several hundred kbps) would also be readily available to this
I don't recommend ultra-wideband if you require high-quality.
> Given that we really don't need the compression levels offered by advanced
> CELP speech encoding, does it still make the most sense to use Speex, or
> would we be better served to use some other codec -- perhaps such as mp2 or
> mp3 -- at higher bitrates?
> Do you have any guidelines you could share?
Use FLAC or Vorbis.
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