[Speex-dev] Increasing the speed of speex playback

[Bill Cox]

Here's one clue about whatever is causing the low quality speech.
Speech sounds terrible at 1.01X faster, and it sounds excellent at
normal speed (1.0X).  So, the main problem is something that breaks
with any change in frame size in the decoder.  Any idea what that
might be?

Thanks,
Bill

On Tue, Oct 19, 2010 at 5:14 PM, Bill  Cox <waywardgeek at gmail.com> wrote:
> I was able to easily hack in an option to play back at different
> speeds.  For example, using "speexdec --speed 2.0 file.enc file.wav"
> plays back encoded file.enc at 2X speed.  What I did was divide
> st->frameSize and st->subFrameSize by the speedup, and added a
> SPEEX_SET_SPEED decoder control for the nb_celp decoder.  This
> produced speech that was 2X faster than the original.
>
> However, the quality is very poor.  This is where it gets harder for
> me, as the quality is impacted by so many parts of the code.  Can
> anyone guess which part of the decoder is leading to such poor quality
> when I cut the frame size in half?  This hack works very well in
> LPC10, and fairly well in MELPe.
>
> I've attached two outputs from speex: the decoded playback at normal
> speed, and the 2X speed version.
>
> Thanks,
> Bill
>