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[英]Read encoded frames from audio file with ExtAudioFileSeek and ExtAudioFileRead
[英]Playing .caf audio file with ExtAudioFileRead is not sync
我的應用程序對來自麥克風輸入的音頻進行了大量數據處理。 為了獲得“演示模式”,我想基於本地.caf音頻文件執行相同的操作。 我設法得到了音頻文件。 現在,我嘗試使用ExtAudioFileRead讀取.caf文件,然后進行數據處理。
void readFile()
{
OSStatus err = noErr;
// Audio file
NSURL *path = [[NSBundle mainBundle] URLForResource:@"output" withExtension:@"caf"];
ExtAudioFileOpenURL((__bridge CFURLRef)path, &audio->audiofile);
assert(audio->audiofile);
// File's format.
AudioStreamBasicDescription fileFormat;
UInt32 size = sizeof(fileFormat);
err = ExtAudioFileGetProperty(audio->audiofile, kExtAudioFileProperty_FileDataFormat, &size, &fileFormat);
// tell the ExtAudioFile API what format we want samples back in
//bzero(&audio->clientFormat, sizeof(audio->clientFormat));
audio->clientFormat.mSampleRate = SampleRate;
audio->clientFormat.mFormatID = kAudioFormatLinearPCM;
audio->clientFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audio->clientFormat.mFramesPerPacket = 1;
audio->clientFormat.mChannelsPerFrame = 1;
audio->clientFormat.mBitsPerChannel = 16;//sizeof(AudioSampleType) * 8;
audio->clientFormat.mBytesPerPacket = 2 * audio->clientFormat.mChannelsPerFrame;
audio->clientFormat.mBytesPerFrame = 2 * audio->clientFormat.mChannelsPerFrame;
err = ExtAudioFileSetProperty(audio->audiofile, kExtAudioFileProperty_ClientDataFormat, sizeof(audio->clientFormat), &audio->clientFormat);
// find out how many frames we need to read
SInt64 numFrames = 0;
size = sizeof(numFrames);
err = ExtAudioFileGetProperty(audio->audiofile, kExtAudioFileProperty_FileLengthFrames, &size, &numFrames);
// create the buffers for reading in data
AudioBufferList *bufferList = malloc(sizeof(AudioBufferList) + sizeof(AudioBuffer) * (audio->clientFormat.mChannelsPerFrame - 1));
bufferList->mNumberBuffers = audio->clientFormat.mChannelsPerFrame;
for (int ii=0; ii < bufferList->mNumberBuffers; ++ii)
{
bufferList->mBuffers[ii].mDataByteSize = sizeof(float) * (int)numFrames;
bufferList->mBuffers[ii].mNumberChannels = 1;
bufferList->mBuffers[ii].mData = malloc(bufferList->mBuffers[ii].mDataByteSize);
}
UInt32 maxReadFrames = 1024;
UInt32 rFrames = (UInt32)numFrames;
while(rFrames > 0)
{
UInt32 framesToRead = (maxReadFrames > rFrames) ? rFrames : maxReadFrames;
err = ExtAudioFileRead(audio->audiofile, &framesToRead, bufferList);
[audio processAudio:bufferList];
if (rFrames % SampleRate == 0)
[audio realtimeUpdate:nil];
rFrames = rFrames - maxReadFrames;
}
// Close the file
ExtAudioFileDispose(audio->audiofile);
// destroy the buffers
for (int ii=0; ii < bufferList->mNumberBuffers; ++ii)
{
free(bufferList->mBuffers[ii].mData);
}
free(bufferList);
bufferList = NULL;
}
顯然有些事情我不理解,或者ExtAudioFileRead我做錯了,因為該代碼根本無法工作。 我有兩個主要問題:
processaudio
和realtimeUpdate
有一些dispatch_sync。 ExtAudioFileRead似乎並沒有真正意識到這一點,它凍結了。 感謝您的幫助。 您編寫的代碼只是從文件中讀取示例,然后調用processAudio。 這將盡快完成。 一旦processAudio完成,將讀取下一批樣本,並再次調用processAudio。 您不應該假設從音頻文件中進行讀取(這是一個低水平且無阻塞的os調用)需要花費與音頻播放相同的時間。 如果要根據采樣率處理文件中的音頻,則可能應該使用AUFilePlayer音頻單元。 這樣可以以正確的速度播放文件,並且您可以使用回調以實時音頻時間處理樣本,而不是“盡可能快”。
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