<FONT size=2> <div>Hi everyone,</div> <div> </div> <div>Our team is working on a realtime voice communication application. We are using openAL 1.1 to capture the samples and then encode them using speex. On the remote machine we decode the samples and play them using openAL again. Capture and play formats for the samples is AL_FORMAT_MONO16 and frequency is 22050. we are using wide band encoding/decoding. </div> <div> </div> <div>The encoding sample frame buffer size is returned by speex as 320, on both ends ( </FONT><FONT face="Courier New" size=2>speex_encoder_ctl(m_poSpeexState, SPEEX_GET_FRAME_SIZE, &nFrameSize) ).</FONT></div> <div><FONT face="Courier New" size=2> </div></FONT><FONT size=2> <div>Coming to the problem, when I play the sound I get a high picthed noise in the background. I do hear my voice with a decreased quality but the noise keeps running in the background whether I talk or not.</div>
<div> </div> <div> </div> <div>Here are the two main encoding/decoding function I am using</div> <div> </div> <div>//------------------------------------------------------------------------------------------</div> <div> </div></FONT><FONT color=#0000ff size=2> <div>void</FONT><FONT size=2> OALCapture::Compress(ALchar* pData, </FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> *iFrameSize, </FONT><FONT color=#0000ff size=2>char</FONT><FONT size=2>* cComFrame)</div> <div>{</div> <div></FONT><FONT color=#008000 size=2>// Reset speex bits before frame encode</div></FONT><FONT size=2> <div>speex_bits_reset(&m_oBits);</div> <div> </div> <div></FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> nFrameSize = 0;</FONT></div> <div><FONT size=2>speex_encoder_ctl(m_poSpeexCompressState, SPEEX_GET_FRAME_SIZE, &nFrameSize);</FONT></div> <div><FONT size=2> </div> <div></FONT><FONT color=#008000 size=2>// Our samples are 2
bytes each so number of samples is actually</div></FONT><FONT size=2> <div></FONT><FONT color=#008000 size=2>// have the buffer size</div></FONT><FONT size=2> <div></FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> nBuffSize = BUFFERSIZE / 2; </FONT></div> <div><FONT size=2> </div> <div></div> <div></FONT><FONT color=#008000 size=2>// Now copy the samples into the float array that we will encode</div></FONT><FONT size=2> <div></FONT><FONT color=#0000ff size=2>for</FONT><FONT size=2>(</FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> i = 0; i < nBuffSize; i++)</div> <div>input[i] = ( (pData[(i*2) + 1] << 8) | (pData[(i*2)] & 0xff) ) / 32768.0f;</div> <div> </div> <div></FONT><FONT color=#008000 size=2>// Provide speex with the float array pointer to compress</div></FONT><FONT size=2> <div>speex_encode(m_poSpeexCompressState, input, &m_oBits);</div> <div> </div> <div></FONT><FONT color=#008000 size=2>// Write the
encoded bytes into our array</div></FONT><FONT size=2> <div>speex_bits_insert_terminator(&m_oBits);</div> <div>nbBytes = speex_bits_write(&m_oBits, cbits, BUFFERSIZE);</div> <div> </div> <div></FONT><FONT color=#008000 size=2>// Set the number of bytes of encoded message</div></FONT><FONT size=2> <div>*iFrameSize = nbBytes;</div> <div> </div> <div></FONT><FONT color=#008000 size=2>// Copy encoded bytes into return array</div></FONT><FONT size=2> <div>memcpy(cComFrame, cbits, nbBytes);</div> <div>}</div> <div> </div> <div>//------------------------------------------------------------------------------------------</div> <div> </div></FONT><FONT color=#0000ff size=2> <div>int</FONT><FONT size=2> OALCapture::Decompress(ALchar* pDecomData, </FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> iFrameSize, </FONT><FONT color=#0000ff size=2>char</FONT><FONT size=2>* cComFrame)</div> <div>{</div> <div></FONT><FONT color=#008000
size=2>// Set the decompress bits</div></FONT><FONT size=2> <div>speex_bits_read_from(&m_oDecompressBits, cComFrame, iFrameSize);</div> <div> </div> <div></div> <div></FONT><FONT color=#008000 size=2>// Decode the bits into an output float array</div></FONT><FONT size=2> <div>speex_decode(m_poSpeexDecompressState, &m_oDecompressBits, output);</div> <div> </div> <div></FONT><FONT color=#008000 size=2>// Get the number of samples returned by the decoder</div></FONT><FONT size=2> <div></FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> nSamplesDecoded = 0;</div> <div>speex_decoder_ctl(m_poSpeexDecompressState, SPEEX_GET_FRAME_SIZE, &nSamplesDecoded);</div> <div> </div> <div></FONT><FONT color=#008000 size=2>//nSamplesDecoded /= 2;</div></FONT><FONT size=2> <div></FONT><FONT color=#008000 size=2>// Now we have to convert the floats back into our AL sample format</div></FONT><FONT size=2> <div></FONT><FONT color=#008000 size=2>//
which takes 2 bytes integer value for each sample</div></FONT><FONT size=2> <div></FONT><FONT color=#0000ff size=2>short</FONT><FONT size=2>* pALBuffer = (</FONT><FONT color=#0000ff size=2>short</FONT><FONT size=2>*) pDecomData;</div> <div></FONT><FONT color=#0000ff size=2>for</FONT><FONT size=2>(</FONT><FONT color=#0000ff size=2>int</FONT><FONT size=2> i = 0; i < nSamplesDecoded; i++)</div> <div>{</div> <div>pALBuffer[i] = output[i] * 32768.0f;</div> <div>}</div> <div> </div> <div>nSamplesDecoded *= 2;</div> <div></FONT><FONT color=#0000ff size=2>return</FONT><FONT size=2> nSamplesDecoded;</div> <div>}</div> <div> </div> <div>//------------------------------------------------------------------------------------------</div> <div>Here are the issues I can think of</div> <div> </div> <div>1.</div> <div>My buffer size is 640 bytes as each sample is of 2 bytes and the frame buffer size if 320 samples as required by speex. I have tried changing
this buffer size and the result is a different type of noise, much worse then what I currently get. </div> <div> </div> <div> </div> <div>Speex returns the same frame size for non-compressed and decompressed data although the quality of decompressed data has reduced.</div> <div> </div> <div>2. </div> <div>Should we get a smaller frame size for low quality decoded data ?</div> <div> </div> <div>3. </div> <div>Is the sound format the same (AL_FORMAT_MONO16, 22050) for both data ?</div> <div> </div> <div>We are in a critical development period, so any quick response will be really helpful to me. </div> <div> </div> <div>Thanks,</div> <div> </div> <div>Ali Khan.</div> <div> </div> <div> </div> <div> </div></FONT><p> 
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