AVAssetExportSession 音视频的剪辑,以及格式的装换

//第一种方式

//asset生成必须为文件的url，而且是本地

AVAsset *mediaAsset = _player.currentItem.asset;

//AVMutableComposition 可以进行音视频的组合

AVAssetExportSession *es = [[AVAssetExportSession alloc] initWithAsset:mediaAsset presetName:AVAssetExportPresetPassthrough];

NSString *outPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"out.mov"];

NSFileManager *fileManager = [NSFileManager defaultManager];

[fileManager removeItemAtPath:outPath error:NULL];

//格式的转换

es.outputFileType = AVFileTypeQuickTimeMovie;

es.outputURL = [[NSURL alloc] initFileURLWithPath:outPath];

es.shouldOptimizeForNetworkUse=NO;

CMTime start = CMTimeMakeWithSeconds(1.0, 600);

CMTime duration = CMTimeMakeWithSeconds(3.0, 600);

CMTimeRange range = CMTimeRangeMake(start, duration);

//音频的时间范围

es.timeRange = range;

NSLog(@"exporting to %@",outPath);

//异步输出完成后调用

[es exportAsynchronouslyWithCompletionHandler:^{

NSString *status = @"" ;

if( es.status == AVAssetExportSessionStatusCompleted ) status = @"AVAssetExportSessionStatusCompleted";

else if( es.status == AVAssetExportSessionStatusFailed ) status = @"AVAssetExportSessionStatusFailed";

NSLog(@"done exporting to %@ status %d = %@ (%@)",outPath,es.status, status,[es error]);

}];

//第二种方式读取本地到另外一个地方

NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];

NSString *audioPath = [documentPath stringByAppendingPathComponent:[NSString stringWithFormat:@"audio"]];

NSURL *fileUrl = [NSURL fileURLWithPath:[NSString stringWithFormat:@"%@/1141.mp3",audioPath]];

AVURLAsset *asset = [[AVURLAsset alloc] initWithURL:fileUrl options:nil];

NSError *error = nil;

NSArray *array=[_player.currentItem.asset tracksWithMediaType:AVMediaTypeAudio];

AVAssetTrack *track=[[_player.currentItem.asset tracksWithMediaType:AVMediaTypeAudio]firstObject];

NSLog(@"%@",_player.currentItem.asset);

assetReader=[[AVAssetReader alloc]initWithAsset:_player.currentItem.asset error:&error];

NSDictionary *readerOutputSettings=@{(id)AVFormatIDKey:@(kAudioFormatLinearPCM)};

//如果读取失败接下来的代码不会执行。

AVAssetReaderTrackOutput *trackOutput=[[AVAssetReaderTrackOutput alloc]initWithTrack:track outputSettings:readerOutputSettings];

[assetReader addOutput:trackOutput];

//先判断read为YES

BOOL read= [assetReader startReading];

NSString *userPath = [audioPath stringByAppendingPathComponent:[NSString stringWithFormat:@"/writer1.wav"]];

NSURL *outputURL=[NSURL fileURLWithPath:userPath];

assetWriter=[[AVAssetWriter alloc]initWithURL:outputURL fileType:AVFileTypeWAVE error:nil];

AudioChannelLayout channelLayout;

memset(&channelLayout, 0, sizeof(AudioChannelLayout));

channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;

//lin PCM需要设置PCM一些相关的属性

NSDictionary *writerOutputSetting=@{(id)AVFormatIDKey:@(kAudioFormatLinearPCM),(id)AVSampleRateKey:[NSNumber numberWithFloat:44100.0],AVNumberOfChannelsKey:[NSNumber numberWithInt: 2],AVLinearPCMBitDepthKey:[NSNumber numberWithInt:16],

AVLinearPCMIsNonInterleaved:[NSNumber numberWithBool:NO],

AVLinearPCMIsFloatKey:[NSNumber numberWithBool:NO],

AVLinearPCMIsBigEndianKey:[NSNumber numberWithBool:NO],AVChannelLayoutKey:[ NSData dataWithBytes:&channelLayout length: sizeof( AudioChannelLayout ) ]};

AVAssetWriterInput *writerInput=[[AVAssetWriterInput alloc]initWithMediaType:AVMediaTypeAudio outputSettings:writerOutputSetting];

[assetWriter addInput:writerInput];

BOOL writer=[assetWriter startWriting];

dispatch_queue_t dispatchQueue=dispatch_queue_create("com/tapharmonic.WriterQueue", NULL);

[assetWriter startSessionAtSourceTime:kCMTimeZero];

[writerInput requestMediaDataWhenReadyOnQueue:dispatchQueue usingBlock:^{

bool complete=NO;

while ([writerInput isReadyForMoreMediaData]&& !complete) {

NSLog(@"%@",assetWriter.error);

CMSampleBufferRef sampleBuffer=[trackOutput copyNextSampleBuffer];

if(sampleBuffer){

BOOL result=[writerInput appendSampleBuffer:sampleBuffer];