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我编写了一个应用程序，它播放来自硬件的声音（就像一个充满一定频率的正弦波的环形缓冲区）。一切正常，我可以正确播放创建的声音，除了周期性的点击（可能在缓冲区的末尾？）和噪音。

我初始化并运行缓冲区：

void Audiooutput::InitializeAudioParameters()
{
    Audio_DataWritten = 0;
    Audio_fragments = 4;
    Audio_channels = 2;
    Audio_BufferSize = 256;
    Audio_Samplerate = 8000;
    Audio_ResamplingFactor = 1;
    Audio_Framesize = 2;
    // (SND_PCM_FORMAT_S16_LE / 8);
    Audio_frames = Audio_BufferSize / Audio_Framesize * Audio_fragments;

    snd_pcm_uframes_t size;
    err = snd_pcm_hw_params_any(pcmPlaybackHandle, hw_params);
    err = snd_pcm_hw_params_set_rate_resample(pcmPlaybackHandle, hw_params, 1);
    //     qDebug()<<a1.sprintf(" % d \t snd_pcm_hw_params_set_rate: %s",Audio_Samplerate,snd_strerror(err));
    err =
        snd_pcm_hw_params_set_format(pcmPlaybackHandle, hw_params,
                     SND_PCM_FORMAT_S16_LE);
    err =
        snd_pcm_hw_params_set_channels(pcmPlaybackHandle, hw_params,
                       Audio_channels);
    err = snd_pcm_hw_params_set_rate_near(pcmPlaybackHandle, hw_params, &Audio_Samplerate, 0);
    //     qDebug()<<a1.sprintf(" % d \t snd_pcm_hw_params_set_rate: %s",Audio_Samplerate,snd_strerror(err));

    if ((err =
         snd_pcm_hw_params_set_periods_near(pcmPlaybackHandle, hw_params,
                        &Audio_fragments, 0)) < 0) {
        qDebug() << a1.sprintf("Error setting # fragments to %d: %s\n",
                       Audio_fragments, snd_strerror(err));
    } else
        qDebug() << a1.sprintf("setting # fragments to %d: %s\n",
                       Audio_fragments, snd_strerror(err));
    err = snd_pcm_hw_params_get_buffer_size(hw_params, &size);
    if ((err =
         snd_pcm_hw_params_set_buffer_size_near(pcmPlaybackHandle,
                            hw_params,
                            &Audio_frames)) < 0) {
        qDebug() << a1.
            sprintf("Error setting buffer_size %d frames: %s",
                Audio_frames, snd_strerror(err));
    } else
        qDebug() << a1.sprintf("setting Buffersize to %d --> %d: %s\n",
                       Audio_BufferSize, Audio_frames,
                       snd_strerror(err));
    Audio_BufferSize = Audio_frames;
    if ((err = snd_pcm_hw_params(pcmPlaybackHandle, hw_params)) < 0) {
        qDebug() << a1.sprintf("Error setting HW params: %s",
                       snd_strerror(err));
    }
    Q_ASSERT(err >= 0);
}

void Audiooutput::ProduceAudioOutput(int n, int mmodes, int totalMModeGates,
         short *sinusValue, short *cosinusValue)
{
    for (int audioSample = 0; audioSample < n;
         audioSample += Audio_ResamplingFactor) {
        currentposition =
            (int)(m_Audio.generalPos % (Audio_BufferSize / 2));
        if (currentposition == 0) {
            QueueAudioBuffer();
            m_Audio.currentPos = 0;
        }
        m_Audio.generalPos++;
        AudioData[currentposition * 2] =
            (short)(sinusValue[audioSample]);
        AudioData[currentposition * 2 + 1] =
            (short)(cosinusValue[audioSample]);
    }
}

void Audiooutput::QueueAudioBuffer()
{
    snd_pcm_prepare(pcmPlaybackHandle);
    Audio_DataWritten +=
        snd_pcm_writei(pcmPlaybackHandle, AudioData, Audio_BufferSize);
}

更改音频缓冲区大小或片段也会更改单击周期。谁能帮我解决这个问题？我还检查了第一个和最后一个值。你总是与众不同。

操作系统：Ubuntu 11

更多详情。

接收数据的数量是动态的，变化取决于不同的参数。但我总是玩某个部分，例如 128 个值或 256 或 512....

// 我从硬件获取音频数据（在 Timerloop 中）

    audiobuffersize  = 256;
    short *AudioData = new short[256];
    int generalAudioSample = 0;

    void CollectDataFromHw()
{  
...  
        int n = 0;
        n = GetData(buf1,buf2);//buf1 = new short[MAX_SHRT]
        if(n > 0)
           FillAudioBuffer(n,buf1,buf2)
...
}
    -------------------------------------------
    void FillAudioBuffer(int n, short*buf1, short*buf2)
    {
      for(int audioSample = 0;audioSample < n; audioSample++){
         iCurrentAudioSample = (int)(generalAudioSample % (audiobuffersize/2)); 
         if(iCurrentAudioSample == 0)  {
            snd_pcm_writei(pcmPlaybackHandle,AudioData,audiobuffersize );
             memset(AudioData,0x00,audiobuffersize*sizeof(short));

         }
        generalAudioSample++;
        AudioData[iCurrentAudioSample * 2]   = (short)(buf1[audioSample];
        AudioData[iCurrentAudioSample * 2 +1]   = (short)(buf2[audioSample];

     }
    }

I changed the audiobuffersize also. If I set it to a bigger size, I have some Echo additional to clicks.

any Idea ? //----------------------- the Problem is 

snd_pcm_prepare(pcmPlaybackHandle);

every call of this function produce a click in sound !

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2 回答 2

2

Can't test the source code, but I think that the high-frequency clicks you hear are discontinuities in the sound wave. You have to assure that looping period (or, buffer size) is multiple of wave period.

Check if first and last value of buffer are almost the same (+/- 1, for example). Their distance determines the amplitude of the unwanted click.

于 2011-11-15T12:04:35.277 回答
1

solved buffer has been played several times before it was filled with the data.

stupid error in the code.missing a parantez --> audio_buffersize/2 <-- and therefore the result was very often if(iCurrentAudioSample == 0) true !!!!!

iCurrentAudioSample = (int)(generalAudioSample % (audio_buffersize/2));
if(iCurrentAudioSample == 0)
{
 writetoaudioStream(audiobuffer);
}
于 2011-12-01T08:15:37.313 回答