[speex-dev] Speex settings and jitter

Conrad Parker conrad at metadecks.org
Wed May 21 21:35:02 PDT 2003

On Tue, May 20, 2003 at 06:04:39PM +0200, Chris Flerackers wrote:
> Hi,
> Is there are document where the interaction between all the configuration
> options of speex is explained?
> Speex seems to have CBR, VBR and ABR. You can also use SPEEX_SET_QUALITY
> (SPEEX_SET_VBR_QUALITY) and SPEEX_SET_BITRATE which I suppose can't be set
> at the same time. Is there a list of possible combinations somewhere?

Hi Chris,

not sure if there's a document describing this, I got the info from
the mail archives and emails with Jean-Marc. This is pretty important
for writing a GUI of course, so here's what I know (as implemented
in Sweep).

nb. this also takes into account DTX, which is basically optional on
top of VAD (setting VBR implies VAD).

As of 1.0, the following option combinations are valid:

        CBR + VAD
        CBR + VAD + DTX
        VBR + VAD (or "VBR without DTX", added in speex-1.0rc3)
        VBR + VAD + DTX (ie. normal VBR)


        for CBR: either SPEEX_SET_QUALITY (int) or SPEEX_SET_BITRATE
        for VBR: either SPEEX_SET_VBR_QUALITY (float) or SPEEX_SET_ABR

AFAIK setting BITRATE or ABR will _override_ QUALITY or VBR_QUALITY

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