麦克风PCM数据实时编码MP3数据的方法

来源：互联网发布：企业级选课系统源码编辑：程序博客网时间：2024/05/22 05:11

最后还是再StackOverFlow上找到的解决办法，StackOverFlow，大赞！！

从麦克风获取PCM数据的方法，参看Apple的官方例子：SpeakHere

注意，以下方法实现的前提是：
录音格式为kAudioFormatLinearPCM；
录音格式的mBitsPerChannel要设置为16

SpeakHere的InputBufferHandler回调方法中，可以获取到PCM数据：

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// AudioQueue callback function, called when an input buffers has been filled.
voidAudioInputBufferHandler( void*                               inUserData,
                              AudioQueueRef                        inAQ,
                              AudioQueueBufferRef                  inBuffer,
                              constAudioTimeStamp *               inStartTime,
                              UInt32                               inNumPackets,
                              constAudioStreamPacketDescription * inPacketDesc ) {
     
    AudioRecorder *recorder = (AudioRecorder *)inUserData;
    try{
         
        if( recorder.isRunning && inNumPackets > 0 ) {
 
            [recorder.mp3Encoder encodePcmData:inBuffer->mAudioData withDataSize:inNumPackets];
            // write packets to file
            /*
            XThrowIfError( AudioFileWritePackets( aqr->mRecordFile,
                                                  FALSE,
                                                  inBuffer->mAudioDataByteSize,
                                                  inPacketDesc,
                                                  aqr->mRecordPacket,
                                                  &inNumPackets,
                                                  inBuffer->mAudioData ),
                           "AudioFileWritePackets failed!");
            aqr->mRecordPacket += inNumPackets;
            */
        }
         
        // if we're not stopping, re-enqueue the buffe so that it gets filled again
        if( recorder.isRunning ) {
             
            XThrowIfError( AudioQueueEnqueueBuffer( inAQ, inBuffer, 0, NULL), @"AudioQueueEnqueueBuffer failed!" );
        }
    }
    catch( NSException*e ) {
 
        [Dialog simpleToast:[NSStringstringWithFormat:@"Error: %@ (%@)\n", [e name], [e reason]]];
        // DLog(@"Error: %@ (%@)\n", [e name], [e reason]);
    }
}

通过[recorder.mp3Encoder encodePcmData:inBuffer->mAudioData withDataSize:inNumPackets];
把PCM数据扔给MP3编码器

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- (void)encodePcmData:(void*)pcmBuffer withDataSize:(UInt32)pcmDataSize {
 
        intmp3DataSize = pcmDataSize * 4;
         
        unsignedcharmp3Buffer[mp3DataSize];
         
        intencodedBytes = lame_encode_buffer( lame, pcmBuffer, pcmBuffer, pcmDataSize, mp3Buffer, mp3DataSize );
        //lame_encode_buffer_interleaved( lame, pcmBuffer, PCM_DATA_SIZE, mp3Buffer, MP3_DATA_SIZE );
         
        NSData*mp3Data = [NSDatadataWithBytes:&mp3Buffer length:encodedBytes];
}

之前在BaiDu上搜了一些文章，都是把PCM文件转成MP3文件的，所用的方法是lame_encode_buffer_interleaved
而且传递数据长度的参数，用的是inBuffer->mAudioDataByteSize
也许转换文件用这个方法可以，也有可能是PCM的格式问题，用这个方法编码出来的数据，有问题，爆音，而且，声音断断续续

在StackOverFlow上找到的方法，用的数据长度参数是inNumPackets，编码方法是lame_encode_buffer
结果大不相同！

我为人人，人人为我！

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