将 pcm 转换为 mp3(使用 LAME)会导致 mp3 文件中"clicks"

Converting pcm to mp3 (using LAME) causes "clicks" in mp3 file

本文关键字：mp3 文件 clicks LAME 转换 pcm 使用      更新时间：2023-10-16

我的应用程序使用LAME将原始PCM数据编码为mp3。但是我有一个问题 - 输出 mp3 包含持续一段时间内的"点击"。像这样：

声音。。。"咔嚓"声.."咔嚓"声.."咔嚓"等...

我尝试了不同版本的LAME，并尝试更改了许多LAME设置，但没有成功。我的应用程序还可以将 pcm 转换为 wav 和 ogg，但此转换器不会导致"点击"。

有一个编码代码（pcm输入包含一个通道数据，pcm已经重采样到44100频率）：

初始化：

lame = lame_init();
lame_set_in_samplerate(lame, 44100);
lame_set_VBR(lame, vbr_abr);//vbr_default
lame_init_params(lame);
//Samples count (do not have any effect on output)
dwSamples=1024;
//mp3 buffer size, if it do not equals dwSamples*2 than output sound getting scaled
dwMP3Buffer=dwSamples*2;
pMP3Buffer = new BYTE[dwMP3Buffer];

写入 pcm 数据

int Mp3Stream :: Write(short * _data, int _size)
{
    if (_size > 0)
    {
        for(int curPos = 0; curPos < _size; curPos += dwMP3Buffer)
        {
            //int size = dwMP3Buffer;
            //if (_size - curPos < dwMP3Buffer)
            //  size = _size - curPos;
            int bytes = lame_encode_buffer(lame, (short *)((char *)_data + curPos), (short *)((char *)_data + curPos), dwSamples, pMP3Buffer, 0);
            IPF_TRACE(1, "MP3 encoder wrote "<<bytes<<" bytes");
            if (bytes<0)
            {
                IPF_TRACE(1, "MP3 encoding failed with code "<<bytes);
                return bytes;
            }
            BOOL bResult = WriteFile(hFile, pMP3Buffer, bytes, &bw, NULL);
            if (!bResult || bytes != bw)
            {
                IPF_TRACE(1, "MP3 write to file failed with code "<<bytes);
            }
        };
    }
}

敲定

int bytes = lame_encode_flush(lame, pMP3Buffer, 0);
    if (bytes<0)
{
    IPF_TRACE(1, "MP3 flush failed with code "<<bytes);
}
BOOL bResult = WriteFile(hFile, pMP3Buffer, bytes, &bw, NULL);
if (!bResult || bytes != bw)
{
    IPF_TRACE(1, "MP3 write to file failed with code "<<bytes);
}
int ret = lame_close(lame);
if (ret < 0) 
{
    IPF_TRACE(1, "MP3 lame close failed with code "<<ret);
}
delete []pMP3Buffer;

声音 -> 单击 -> 声音 -> 单击模式很可能意味着您一次只写入缓冲区的一半，另一半在写入调用中的每个循环中保持零。

原因是您的循环增量器基于 dwSamples*2 的 dwMP3Buffer 值。

 for(int curPos = 0; curPos < _size; curPos += dwMP3Buffer){

这意味着您实际上并没有对所有输入值进行编码，因为 dwMP3Buffer 是您实际传递给lame_encode_buffer调用 （dwSamples） 的样本数的两倍。

lame_encode_buffer(lame, (short *)((char *)_data + curPos), 
                   (short *)((char *)_data + curPos), dwSamples, pMP3Buffer, 0);

尝试将循环增量器更改为以下内容：

 for(int curPos = 0; curPos < _size; curPos += dwSamples){

试试这个，

void AQRecorder::MyInputBufferHandler(  void *                              inUserData,
                                AudioQueueRef                       inAQ,
                                AudioQueueBufferRef                 inBuffer,
                                const AudioTimeStamp *              inStartTime,
                                UInt32                              inNumPackets,
                                const AudioStreamPacketDescription* inPacketDesc)
{
AQRecorder *aqr = (AQRecorder *)inUserData;
//    NSLog(@"%f",inStartTime->mSampleTime);
try
{
    if (inNumPackets > 0)
    {
        AudioFileWritePackets(aqr->mRecordFile, FALSE, inBuffer->mAudioDataByteSize, inPacketDesc, aqr->mRecordPacket, &inNumPackets, inBuffer->mAudioData);
        aqr->mRecordPacket += inNumPackets;
        int MP3_SIZE =inBuffer->mAudioDataByteSize * 4;
        unsigned char mp3_buffer[MP3_SIZE];
        AppDelegate *delegate =[[UIApplication sharedApplication]delegate];
        lame_t lame = lame_init();
        lame_set_in_samplerate(lame, 44100);
        lame_set_VBR(lame, vbr_default);
        lame_init_params(lame);
  //                int encodedBytes=lame_encode_buffer_interleaved(lame, (short int *)inBuffer->mAudioData , inNumPackets, mp3_buffer, MP3_SIZE);

        int encodedBytes = lame_encode_buffer(lame, (short*)inBuffer->mAudioData,  (short*)inBuffer->mAudioData, inNumPackets, mp3_buffer, MP3_SIZE);
        [delegate.mp3AudioData appendBytes:mp3_buffer length:encodedBytes];
        if (inBuffer->mAudioDataByteSize != 0) {
        }
        else
        {
            int encode=lame_encode_flush(lame, mp3_buffer, MP3_SIZE);
            [delegate.mp3AudioData appendBytes:mp3_buffer length:encode];
        }
        lame_close(lame);
    }
    if (aqr->IsRunning())
    {
        AudioQueueEnqueueBuffer(inAQ, inBuffer, 0, NULL);
    }
 } catch (CAXException e)
 {
 char buf[256];
 fprintf(stderr, "Error: %s (%s)n", e.mOperation, e.FormatError(buf));
}
}

我会尝试设置

dwSamples = 1152

1152 - 是 MPEG1Audio 编码器的音频帧大小（以样本为单位）。看起来LAME通过帧多个块处理数据

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