[opus] High noise after encoding/decoding procedure

Aleksandr Mikoff sir.enmity at gmail.com
Thu Jul 14 12:00:39 UTC 2016

Thanks a lot for your tips.
What I have to done to debug: got the raw wav-file, compressed/decompressed
it on my PC and saved OPUS packets as an array. Moved this array to the
embedded platform and made sure that the frames decoded from the OPUS
packets are the same. However, the high noise level was the same, but it
wasn`t caused by OPUS.
The problem was with my sound bus between an embedded device and the
speaker - there was an one bit offset between FS signal and sound slots,
which I didn't take into account. Now I have the clear enough sound with
30% MCU load for full duplex sound.

2016-07-12 20:46 GMT+03:00 Ralph Giles <giles at thaumas.net>:

> On 2016-07-12 9:34 AM, Aleksandr Mikoff wrote:
> > If I encode each frame, decode it and send it back to the speakers I
> > hear a very noisy signal - it is so large, so it is almost impossible to
> > distinguish words in my speech...
> This effect can be caused by some data type issues:
>  - If you are using opus_encode() and opus_decode(), make sure to use
> 16-bit signed integer samples in the pcm buffer. If you have 8-bit
> samples you'll have to convert them.
>  - Make sure you're passing the length of the pcm buffer in _samples_
> not _bytes_.
>  - Make sure you're passing the size of the compressed opus data in
> _bytes_.
> > Is it ok, that I changed few parameters in "defines.h" file (to
> > suppress the RAM requirements - I have only 60 KB RAM free on my STM32
> > board)? I changed the ENCODER_NUM_CHANNELS 1 and DECODER_NUM_CHANNELS to
> > one, and MAX_FS_KHZ to 8.
> That's not a tested configuration, so it's possible this broke
> something. If you make the same changes and build for a desktop target,
> does audio round-trip through opus_demo correctly?
>  -r
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С уважением,
Миков Александр

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