[opus] inbandfec is adding samples

[Jean-Marc Valin]

Hi,

This issue should be fixed in git master and in 1.1-beta, which will
hopefully be released very soon.

Cheers,

	Jean-Marc

On 11/07/13 04:57 PM, Marc Lindahl wrote:
> I didn't expect this, is it normal?  When you use inbandfec, and have packet losses, you end up with more audio samples than you started with.
> 
> With short frame (2.5), the FEC isn't supposed to do anything but it shouldn't do that should it?  and 20mS frame, should do 'something' but… add audio?
> 
> I'm using opus_demo for this.
> 
> Here's the steps (I have my test audio in it's own folder, parallel with opus and sox):
> 
> make raw audio:
> 
> ../sox-14.4.1/sox music_orig.wav -t raw music_orig.raw
> 
> try a few different encodings:
> 
> ../opus-1.1-alpha/opus_demo audio 48000 2 128000 -framesize 2.5 -loss 10 -inbandfec music_orig.raw music_orig_f2.5_b128000_lr10_fec.raw 
> ../opus-1.1-alpha/opus_demo audio 48000 2 128000 -framesize 2.5 -loss 10  music_orig.raw music_orig_f2.5_b128000_lr10.raw
> ../opus-1.1-alpha/opus_demo audio 48000 2 128000 -framesize 20 -loss 10 -inbandfec music_orig.raw music_orig_f20_b128000_lr10_fec.raw 
> ../opus-1.1-alpha/opus_demo audio 48000 2 128000 -framesize 20 -loss 10  music_orig.raw music_orig_f20_b128000_lr10.raw
> 
> (note - sometimes you get 'error decoding frame: buffer too small' message…)
> 
> check file sizes:
> 
> ls -lsh music_orig* 
>   34056 -rw-r--r--  1 mlindahl  staff    17M Jul 11 15:53 music_orig.raw
>   34056 -rw-r--r--  1 mlindahl  staff    17M Sep  4  2012 music_orig.wav
>   34048 -rw-r--r--  1 mlindahl  staff    17M Jul 11 15:59 music_orig_f2.5_b128000_lr10.raw
> 179408 -rw-r--r--  1 mlindahl  staff    88M Jul 11 15:57 music_orig_f2.5_b128000_lr10_fec.raw
>   34048 -rw-r--r--  1 mlindahl  staff    17M Jul 11 16:49 music_orig_f20_b128000_lr10.raw
>   49192 -rw-r--r--  1 mlindahl  staff    24M Jul 11 16:01 music_orig_f20_b128000_lr10_fec.raw
> 
> 
> Notice the FEC files are significantly longer.  They also sound very odd, like frames are being repeated…
> 
> Im I doing something wrong or….?
> 
> Regards,
> Marc
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