[Speex-dev] Sampling Rate
alainm at pobox.com
Wed Dec 13 15:05:36 PST 2006
What would be speex configuration recomended for Telefone/Voip quality
voice? With a quality just a little better/similar then G.729? or GSM?
is there a comparison chart somewhere, but telephone quality oriented?
Tom Grandgent escreveu:
> Speex was designed for 8kHz, 16kHz, and 32kHz sample rates. If you
> don't use one of these sample rates, you'll be messing up important
> assumptions deep within the codec. Why these sample rates? It's
> telecommunications tradition, rather than PC audio tradition.
> If you want an efficient and high quality format for voice chat, try
> 16kHz with VBR quality 6. You should see around a 10:1 compression
> ratio when someone is talking. That is, around 25kbps would be a
> rough peak using these settings.
> If that's too much bandwidth for you, you can cut it by almost half
> using VBR quality 2. (The loss of quality will be noticible to most
> people using headsets. It is less noticible when using speakers.)
> For further bandwidth savings you could use 8kHz, but it's too much
> of a quality hit to be worth it in my opinion.
> <khaynes at kirkgames.com> wrote:
>> I'm attempting to use speex for voice chat in my game.
>> I'm capturing audio from the mic using OpenAL 1.1 in 16 bit mono. What
>> sample rate is recommended for capturing from the mic? Which would be
>> better: 11025 samples per second, or 22050 samples per second of 16 bit
>> mono audio with respect to then encoding/decoding it with speex? I'm
>> using 11025 to reduce bandwidth at the moment to capture.
>> Given your answer to the above question, what is the most efficient
>> frame size for encoding the samples to speex frames? The sample code
>> uses 160 samples (320 bytes) of 16 bit audio samples, which are then
>> encoded to 200 bytes of encoded data. Is a 30% reduction in data pretty
>> standard? How do I use speex most efficiently?
>> Speex-dev mailing list
>> Speex-dev at xiph.org
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> Speex-dev at xiph.org
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