Correct decoding opus - portaudio

Question

I had a need to transmit sound over the network and for this I chose libraries "PortAudio" and "Opus". I am new to working with sound and therefore i don’t know many thing.I am new to working with sound and therefore i don’t know many things, but i read the documentation and looked at some examples, but i still have some problems with encoding/decoding with Opus. I do not understand how to correctly restore the original encoded PСM.I have some sequence of actions:
Some consts
const int FRAMES_PER_BUFFER = 960;
const int SAMPLE_RATE = 48000;
int NUM_CHANNELS = 2;
int totalFrames = 2 * SAMPLE_RATE; /* Record for a few seconds. */
int numSamples = totalFrames * 2;
int numBytes = numSamples * sizeof(float);
float *sampleBlock = nullptr;
int bytesOfPacket = 0;
unsigned char *packet = nullptr;
I get PСM to sampleBlock
paError = Pa_ReadStream(**&stream, sampleBlock, totalFrames);
if (paError != paNoError) {
cout << "PortAudio error : " << Pa_GetErrorText(paError) << endl;
std::system("pause");
}
Encoding sampleBlock
OpusEncoder *encoder;
int error;
int size;
encoder = opus_encoder_create(SAMPLE_RATE, NUM_CHANNELS, OPUS_APPLICATION_VOIP, &error);
size = opus_encoder_get_size(NUM_CHANNELS);
encoder = (OpusEncoder *)malloc(size);
packet = new unsigned char[480];
error = opus_encoder_init(encoder, SAMPLE_RATE, NUM_CHANNELS, OPUS_APPLICATION_VOIP);
if (error == -1) {
return -1;
}
bytesOfPacket = opus_encode_float(encoder, sampleBlock, FRAMES_PER_BUFFER, packet, 480);
opus_encoder_destroy(encoder);
Ok, i received a encoded packet to Opus
Decoding
OpusDecoder *decoder;
int error;
int size;
decoder = opus_decoder_create(SAMPLE_RATE, NUM_CHANNELS, &error);
size = opus_decoder_get_size(NUM_CHANNELS);
decoder = (OpusDecoder *)malloc(size);
error = opus_decoder_init(decoder, SAMPLE_RATE, NUM_CHANNELS);
opus_decode_float(decoder, packet, bytesOfPacket, sampleBlock, 480, 0);
opus_decoder_destroy(decoder);
Here i am trying to decode the Opus back to the PCM and save the result to the sampleBlock
Playing the sound
paError = Pa_WriteStream(**&stream, sampleBlock, totalFrames);
if (paError != paNoError) {
cout << "PortAudio error : " << Pa_GetErrorText(paError) << endl;
std::system("pause");
}
I get silence. I don't really understand the subtleties in working with sound since i am new to this business. Help please understand what is wrong.

Answer 1

As for your settings you're encoding 20ms of audio per opus_encode_float call. I don't see any iteration over this call so I suppose you don't hear anything because you encode only 20ms of audio. You should pass to opus_encode_float 20ms worth of samples with your sampleBlock pointer incrementing it through the whole buffer x times.
Try to encode more audio and remember that you have to add some sort of framing to decode it. You cannot just feed the whole buffer to the decoder. You should feed the decoder one time for each encoder call with the same data that each encoder call outputs.
Damiano