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I'm trying to decode array of bytes from DSP TrueSpeech to PCM. When we convert this array as part of streaming (divide it to packets) we can hear some strange "Beep" tones after the decoding.

We tried to decode the entire WAV file in one piece and we didn't get those Beeps. Currently we are using Alvas.net for it, but we tried also with NAudio and got the same reaults?

My questions: 1)Is anyone familiar with this kind of behavior? 2)Do you have an idea what can we do?

Thanks Ziv

user3741946
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2 Answers2

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How are you performing the decode? Often codecs maintain internal state, so it's important that you don't keep closing and re-opening the codec for each block of audio that you receive. In NAudio, that means just one AcmStream/WaveFormatConversionStream that everything you receive is passed through.

Also, make sure it is only compressed audio that is being passed into the codec. Sometimes when you receive audio over the network it is contained within some kind of larger packet that contains timing or encoding metadata (e.g. RTP).

Mark Heath
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At the bottom line, we have the packet data(array of bytes) which we are sending to decode (return as PCM) and then we're writing the new decoded array of bytes in to the new WAV file.

We're defiantly going to try your suggestion regarding the stream with NAudio.

Regarding the bytes we're working on, they don't contain any garbage. We've wrote a tester that stream the file directly (without network) and got the same beep results.

Our solution is working so well with many other codecs (GSM and etc..) and only in true speech we're having this problem. Therefore it seems to be like some behavior of True Speech codec, but we didn't find any documentation about it. Thanks Again Ziv

user3741946
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