[Speex-dev] seeking in time, feedback+question

Jim Crichton jim.crichton at comcast.net
Mon Jun 26 09:47:19 PDT 2006

> I was trying to compress some big files and then to
> access to small portions and decode only those parts.
> I use the streaming mode(the sample codes provided on
> the web-site) without the Ogg packaging which seems
> useful to me for seeking in time.
> When I seek in time by just skipping packages, reset
> by:
> speex_decoder_ctl(state, SPEEX_RESET_STATE, NULL);
> and starting decoding, I see that the quality of
> decoding varies depending on the initial frame
> characteristics. It seems that the signal gets close
> to the original quite fast when the first frames are
> unvoiced. If I start decoding in the middle of a
> voiced chunk then decoding quality is comperatively
> much lower, more frames are needed until the signal
> gets closer to the original.
> This was the feedback part. So the obvious question
> is:
> do you know an easy way to get rid of this problem?

I do not know how you could get rid of the problem, but you could mask it by 
starting the decode a few frames early, and throwing away the audio for 
those early frames.  Then the decode state will have converged when you 
start decoding the audio that you want.


Jim Crichton 

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