【发布时间】：2013-12-13 02:07:19
【问题描述】：
我不得不将大文件大小的歌曲从 iTunes 库转换为较小的 8K 歌曲文件。
当我进行异步转换时，即使没有完成对 doc 文件夹的写入，布尔值也始终返回 true。目前我在再次调用该函数之前使用了 10 秒的延迟，它在 iPhone 5s 的过渡期间工作正常，但我想迎合速度较慢的设备。
请给我一些关于我的代码的指针/建议。
-(void)startUploadSongAnalysis
{
[self updateProgressYForID3NForUpload:NO];
if ([self.uploadWorkingAray count]>=1)
{
Song *songVar = [self.uploadWorkingAray objectAtIndex:0];//core data var
NSLog(@"songVar %@",songVar.songName);
NSLog(@"songVar %@",songVar.songURL);
NSURL *songU = [NSURL URLWithString:songVar.songURL]; //URL of iTunes Lib
// self.asset = [AVAsset assetWithURL:songU];
// NSLog(@"asset %@",self.asset);
NSError *error;
NSString *subString = [[songVar.songURL componentsSeparatedByString:@"id="] lastObject];
NSString *savedPath = [self.documentsDir stringByAppendingPathComponent:[NSString stringWithFormat:@"audio%@.m4a",subString]];//save file name of converted 8kb song
NSString *subStringPath = [NSString stringWithFormat:@"audio%@.m4a",subString];
if ([self.fileManager fileExistsAtPath:savedPath] == YES)
[self.fileManager removeItemAtPath:savedPath error:&error];
NSLog(@"cacheDir %@",savedPath);
//export low bitrate song to cache
if ([self exportAudio:[AVAsset assetWithURL:songU] toFilePath:savedPath]) // HERE IS THE PROBLEM, this return true even the writing is not completed cos when i upload to my web server, it will say song file corrupted
{
// [self performSelector:@selector(sendSongForUpload:) withObject:subStringPath afterDelay:1];
[self sendRequest:2 andPath:subStringPath andSongDBItem:songVar];
}
else
{
NSLog(@"song too short, skipped");
[self.uploadWorkingAray removeObjectAtIndex:0];
[self.songNotFoundArray addObject:songVar];
[self startUploadSongAnalysis];
}
}
else //uploadWorkingAray empty
{
NSLog(@"save changes");
[[VPPCoreData sharedInstance] saveAllChanges];
}
}
#pragma mark song exporter to doc folder
- (BOOL)exportAudio:(AVAsset *)avAsset toFilePath:(NSString *)filePath
{
CMTime assetTime = [avAsset duration];
Float64 duration = CMTimeGetSeconds(assetTime);
if (duration < 40.0) return NO; // if song too short return no
// get the first audio track
NSArray *tracks = [avAsset tracksWithMediaType:AVMediaTypeAudio];
if ([tracks count] == 0) return NO;
NSError *readerError = nil;
AVAssetReader *reader = [[AVAssetReader alloc] initWithAsset:avAsset error:&readerError];
//AVAssetReader *reader = [AVAssetReader assetReaderWithAsset:avAsset error:&readerError]; // both works the same ?
AVAssetReaderOutput *readerOutput = [AVAssetReaderAudioMixOutput
assetReaderAudioMixOutputWithAudioTracks:avAsset.tracks
audioSettings: nil];
if (! [reader canAddOutput: readerOutput])
{
NSLog (@"can't add reader output...!");
return NO;
}
else
{
[reader addOutput:readerOutput];
}
// writer AVFileTypeCoreAudioFormat AVFileTypeAppleM4A
NSError *writerError = nil;
AVAssetWriter *writer = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:filePath]
fileType:AVFileTypeAppleM4A
error:&writerError];
//NSLog(@"writer %@",writer);
AudioChannelLayout channelLayout;
memset(&channelLayout, 0, sizeof(AudioChannelLayout));
channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
// use different values to affect the downsampling/compression
// NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
// [NSNumber numberWithInt: kAudioFormatMPEG4AAC], AVFormatIDKey,
// [NSNumber numberWithFloat:16000.0], AVSampleRateKey,
// [NSNumber numberWithInt:2], AVNumberOfChannelsKey,
// [NSNumber numberWithInt:128000], AVEncoderBitRateKey,
// [NSData dataWithBytes:&channelLayout length:sizeof(AudioChannelLayout)], AVChannelLayoutKey,
// nil];
NSDictionary *outputSettings = @{AVFormatIDKey: @(kAudioFormatMPEG4AAC),
AVEncoderBitRateKey: @(8000),
AVNumberOfChannelsKey: @(1),
AVSampleRateKey: @(8000)};
AVAssetWriterInput *writerInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeAudio outputSettings:outputSettings];
//\Add inputs to Write
NSParameterAssert(writerInput);
NSAssert([writer canAddInput:writerInput], @"Cannot write to this type of audio input" );
if ([writer canAddInput:writerInput])
{
[writer addInput:writerInput];
}
else
{
NSLog (@"can't add asset writer input... die!");
return NO;
}
[writerInput setExpectsMediaDataInRealTime:NO];
[writer startWriting];
[writer startSessionAtSourceTime:kCMTimeZero];
[reader startReading];
__block UInt64 convertedByteCount = 0;
__block BOOL returnValue;
__block CMSampleBufferRef nextBuffer;
dispatch_queue_t mediaInputQueue = dispatch_queue_create("mediaInputQueue", NULL);
[writerInput requestMediaDataWhenReadyOnQueue:mediaInputQueue usingBlock:^{
// NSLog(@"Asset Writer ready : %d", writerInput.readyForMoreMediaData);
while (writerInput.readyForMoreMediaData)
{
nextBuffer = [readerOutput copyNextSampleBuffer];
if (nextBuffer)
{
[writerInput appendSampleBuffer: nextBuffer];
convertedByteCount += CMSampleBufferGetTotalSampleSize (nextBuffer);
//NSNumber *convertedByteCountNumber = [NSNumber numberWithLong:convertedByteCount];
//NSLog (@"writing");
CFRelease(nextBuffer);
}
else
{
[writerInput markAsFinished];
[writer finishWritingWithCompletionHandler:^{
if (AVAssetWriterStatusCompleted == writer.status)
{
NSLog(@"Writer completed");
returnValue = YES; //I NEED TO RETURN SOMETHING FROM HERE AFTER WRITING COMPLETED
dispatch_async(mediaInputQueue, ^{
dispatch_async(dispatch_get_main_queue(), ^{
// add this to the main queue as the last item in my serial queue
// when I get to this point I know everything in my queue has been run
NSDictionary *outputFileAttributes = [[NSFileManager defaultManager]
attributesOfItemAtPath:filePath
error:nil];
NSLog (@"done. file size is %lld",
[outputFileAttributes fileSize]);
});
});
}
else if (AVAssetWriterStatusFailed == writer.status)
{
[writer cancelWriting];
[reader cancelReading];
NSLog(@"Writer failed");
return;
}
else
{
NSLog(@"Export Session Status: %d", writer.status);
}
}];
break;
}
}
}];
tracks = nil;
writer = nil;
writerInput = nil;
reader = nil;
readerOutput=nil;
mediaInputQueue = nil;
return returnValue;
//return YES;
}
【问题讨论】：
标签： ios objective-c nsdocument avassetwriter avassetexportsession