Question

I have a problem when try to achieve smooth audio playback using waveOutWrite(). My data includes many adpcmdata bocks which gotten from camera, after decoded each adpcm block I play it by using waveOutWrite(). The first block is played succesfully (atleast i can heard) but i have problem when I play for next block that exist a gap between these blocks. I tried to call sleep() after using waveOutWrite() but it’s not ok. Anybody can tell me how i get smooth in this case? Any problem in the way that i playback the audio?

for (i = 0, i < MaxBlockData, i++)  


        BYTE * pcmBuff = new BYTE[length*8];
        memset(pcmBuff, 0, length*8);
        G726 g726;

        int pcmDataSize = 0;
        g726.SetRate(g726.Rate32kBits);
        g726.SetLaw(g726.PCM16);
        pcmDataSize = g726.Decode(pcmBuff, adpcmData[i], 0, length*8); /decode adcmData PCM 16

        if(pcmDataSize > 0)
        {
            int sampleRate = 8000;
            CHAR* waveIn = new CHAR[pcmDataSize];

            HWAVEIN hWaveIn;
            WAVEHDR WaveInHdr;
            MMRESULT result;
            HWAVEOUT hWaveOut;

            WAVEFORMATEX pFormat;
            pFormat.wFormatTag = WAVE_FORMAT_PCM;
            pFormat.nChannels = 1;
            pFormat.nSamplesPerSec = sampleRate;
            pFormat.nAvgBytesPerSec = 2 * sampleRate;
            pFormat.nBlockAlign = 2;
            pFormat.wBitsPerSample = 16;
            pFormat.cbSize = 0;

            result = waveInOpen(&hWaveIn, WAVE_MAPPER, &pFormat, 0, 0, WAVE_FORMAT_DIRECT);

            if(result != MMSYSERR_NOERROR)
            {
                char fault[256];
                waveInGetErrorTextA(result, fault, 256);
                MessageBoxA(NULL, fault, "Failed to open waveform input device.", MB_OK | MB_ICONEXCLAMATION);
                return;
            }

            WaveInHdr.lpData = (LPSTR)waveIn;
            WaveInHdr.dwBufferLength = pcmDataSize;
            WaveInHdr.dwBytesRecorded = 0;
            WaveInHdr.dwUser = 0;
            WaveInHdr.dwFlags = 0;
            WaveInHdr.dwLoops = 0;

            waveInPrepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));
            memcpy(WaveInHdr.lpData, pcmBuff, pcmDataSize);

            if(waveOutOpen(&hWaveOut, WAVE_MAPPER, &pFormat, 0, 0, WAVE_FORMAT_DIRECT))
            {
                MessageBoxA(NULL, "Failed to replay", NULL, MB_OK | MB_ICONEXCLAMATION );
            }

            waveOutWrite(hWaveOut, &WaveInHdr, sizeof(WaveInHdr)); 
            Sleep((pcmDataSize/sampleRate ) * 1000); //Sleep for as long as there was recorded

            waveOutUnprepareHeader(hWaveOut, &WaveInHdr, sizeof(WAVEHDR));
            waveInUnprepareHeader(hWaveIn, &WaveInHdr, sizeof(WAVEHDR));
            waveInClose(hWaveIn);
            waveOutClose(hWaveOut);


            WaveInHdr.lpData = NULL;
            delete []waveIn;
        }
    }

Thanks for reading my question.

Answer 1

I won’t work like this.
when you play first sample you can’t sleep for the time of your next samples, instead you should use double or multi buffering and a callback mechanism.
the overall protocol is as follow:
1) get first block from camera or whatever
2) get second block from camera or whatever
3) write first block and then second block without any wait.
then create a loop that wait for signals from callbackand upon receiving signals write next captured block.