如何使用NSInputStream和NSOutputStream读取和写入音频文件

Question

I record and save the caf audio file using AVAudioRecorder. When I convert the (300 mb).caf to .wav format the Application crashed with error(Received memory warning. Level=1 and Received memory warning. Level=2). How to use NSInputStream for reading audio file and NSOutputStream for writing audio file.

-(void) convertToWav:(NSNumber *) numIndex
{
// set up an AVAssetReader to read from the iPod Library
int index = [numIndex integerValue];

NSString *strName;
NSString *strFilePath1 =[delegate.strCassettePathSide stringByAppendingPathComponent:@"audio_list.plist"];

bool bTapeInfoFileExists = [[NSFileManager defaultManager] fileExistsAtPath:strFilePath1];

if (bTapeInfoFileExists)
{
    NSMutableDictionary *dictInfo = [[NSMutableDictionary alloc] initWithContentsOfFile:strFilePath1];

    if ([dictInfo valueForKey:@"lastName"])
        strName =[dictInfo valueForKey:@"lastName"];
    else
        strName= [delegate.arrNameList objectAtIndex:0];
}
else
{
    strName = [delegate.arrNameList objectAtIndex:0];
}

NSString *cafFilePath =[[delegate.arrSessionList objectAtIndex:index] valueForKey:@"path"];
NSURL *assetURL = [NSURL fileURLWithPath:cafFilePath];
AVURLAsset *songAsset = [AVURLAsset URLAssetWithURL:assetURL options:nil];

NSError *assetError = nil;
AVAssetReader *assetReader = [AVAssetReader assetReaderWithAsset:songAsset
                                                           error:&assetError]
;
if (assetError) {
    NSLog (@"error: %@", assetError);
    return;
}

AVAssetReaderOutput *assetReaderOutput = [AVAssetReaderAudioMixOutput
                                          assetReaderAudioMixOutputWithAudioTracks:songAsset.tracks
                                          audioSettings: nil];
if (! [assetReader canAddOutput: assetReaderOutput]) {
    NSLog (@"can't add reader output... die!");
    return;
}
[assetReader addOutput: assetReaderOutput];

NSString *strWavFileName = [NSString stringWithFormat:@"%@.wav",[[cafFilePath lastPathComponent] stringByDeletingPathExtension]];
NSString *wavFilePath = [delegate.strCassettePathSide stringByAppendingPathComponent:strWavFileName];

if ([[NSFileManager defaultManager] fileExistsAtPath:wavFilePath])
{
    [[NSFileManager defaultManager] removeItemAtPath:wavFilePath error:nil];
}
NSURL *exportURL = [NSURL fileURLWithPath:wavFilePath];
AVAssetWriter *assetWriter = [AVAssetWriter assetWriterWithURL:exportURL
                                                      fileType:AVFileTypeWAVE
                                                         error:&assetError];
if (assetError)
{
    NSLog (@"error: %@", assetError);
    return;
}

AppDelegate *appDelegate =[[UIApplication sharedApplication]delegate];
int nSampleRate=[[appDelegate.dictWAVQuality valueForKey:@"samplerate"] integerValue];
AudioChannelLayout channelLayout;
memset(&channelLayout, 0, sizeof(AudioChannelLayout));
channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                [NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey,
                                [NSNumber numberWithFloat:nSampleRate], AVSampleRateKey,
                                [NSNumber numberWithInt:2], AVNumberOfChannelsKey,
                                [NSData dataWithBytes:&channelLayout length:sizeof(AudioChannelLayout)], AVChannelLayoutKey,
                                [NSNumber numberWithInt:16], AVLinearPCMBitDepthKey,
                                [NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved,
                                [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,
                                [NSNumber numberWithBool:NO], AVLinearPCMIsBigEndianKey,
                                nil];
AVAssetWriterInput *assetWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio
                                                                          outputSettings:outputSettings];
if ([assetWriter canAddInput:assetWriterInput])
{
    [assetWriter addInput:assetWriterInput];
}
else
{
    NSLog(@"can't add asset writer input... die!");
    return;
}

assetWriterInput.expectsMediaDataInRealTime = NO;

[assetWriter startWriting];
[assetReader startReading];

AVAssetTrack *soundTrack = [songAsset.tracks objectAtIndex:0];
CMTime startTime = CMTimeMake (0, soundTrack.naturalTimeScale);
[assetWriter startSessionAtSourceTime: startTime];

__block UInt64 convertedByteCount = 0;
dispatch_queue_t mediaInputQueue = dispatch_queue_create("mediaInputQueue", NULL);

[assetWriterInput requestMediaDataWhenReadyOnQueue:mediaInputQueue
                                        usingBlock: ^
 {
     while (assetWriterInput.readyForMoreMediaData)
     {
         CMSampleBufferRef nextBuffer = [assetReaderOutput copyNextSampleBuffer];
         if (nextBuffer)
         {
             // append buffer
             [assetWriterInput appendSampleBuffer: nextBuffer];
             convertedByteCount += CMSampleBufferGetTotalSampleSize (nextBuffer);
         }
         else
         {
             [assetWriterInput markAsFinished];
             //              [assetWriter finishWriting];
             [assetReader cancelReading];

             [dictTemp setValue:wavFilePath forKey:@"path"];
             [dictTemp setValue:nil forKey:@"progress"];
             [delegate.arrSessionList replaceObjectAtIndex:index withObject:dictTemp];

             NSString *strListFilePath = [delegate.strCassettePathSide stringByAppendingPathComponent:@"audiolist.plist"];
             [delegate.arrSessionList writeToFile:strListFilePath atomically:YES];
             break;
         }
     }
 }];}

Answer 1

i assumed you are using ARC, you need to release the buffer.

Core Foundation does not release by ARC as per the “The Create Rule” in Memory Management Programming Guide for Core Foundation. You have to release CMSampleBufferRef obtained from -(CMSampleBufferRef)copyNextSampleBuffer or you will get a memory leak.

https://developer.apple.com/library/mac/documentation/CoreFoundation/Conceptual/CFMemoryMgmt/Concepts/Ownership.html#//apple_ref/doc/uid/20001148-103029


if (nextBuffer)
         {
             // append buffer
             [assetWriterInput appendSampleBuffer: nextBuffer];
             convertedByteCount += CMSampleBufferGetTotalSampleSize (nextBuffer);
             CFRelease(nextBuffer);
         }