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IPP G729 silence decoded wrong



I'm using the IPP API to encode and decode G729 audio.

Until now, I used the available documentation and the internet topics in order to make possible the use of the G729 library.

I have an issue regarding the silence periods and I think the problem is on the encoder side, but I can't figure out where.

When I decode the G729 encoded audio, the silence periods are decoded as a combination of stationary signals.

The result presents a major discomfort and is very noisy.

The time series and the spectrum are listed below.

- time series:

- frequency spectrum:

As you can see, the dominant frequency is around 200Hz and has a power level of -39dB.

Moreover, I tried to decode the audio encoded with the IPP library, with other G729 libraries and I remarked that the result is the same.

Notice that the voice is clear and is not affected in any way.

I think the problem is regarding the comfort noise generator (CNG). In my opinion, the silence is encoded in a different way and is decoded in the same way as the voice is decoded.

Any help is appreciated.

Thank you,

Best regards!


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