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];
CFRelease(sampleBuffer);
complete=!result;
}else{
[writerInput markAsFinished];
complete=YES;
}
}
if(complete){
[assetWriter finishWritingWithCompletionHandler:^{
AVAssetWriterStatus status=assetWriter.status;
NSLog(@"%@",assetWriter.error);
if(status==AVAssetWriterStatusCompleted){
NSLog(@"AVAssetWriterStatusCompleted");
}else{
NSLog(@"AVAssetWriterStatusFailed");
}
}];
}
}];
AVAssetExportSession你可以取消这个生成操作，通过给session发送 cancelExport 消息。
失败原因：
· 如果导出的文件存在，或者导出的url在沙盒之外，这个导出操作会失败。
· 来了一个电话
· 你的程序在后台运行并且其他的应用开始播放。
这种情况下，你应该通知用户export失败，并且重新export。