ios - AVFoundation：从文件中读取视频——处理帧+音频并重新输出

Question

我一直在努力解决这个问题，但无法弄清楚我做错了什么。我想读取一个视频文件——处理帧......然后重新输出它：

我面临的问题是，由于某种原因，对 [self.audioOutput copyNextSampleBuffer]; 的调用会阻塞并且永远不会完成！

-(void) initializeAtPath:(NSURL*) inputPath withOutputPath:(NSURL*) outputPath{    
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               AVVideoCodecH264, AVVideoCodecKey,
                               [NSNumber numberWithInt:352], AVVideoWidthKey,
                               [NSNumber numberWithInt:288], AVVideoHeightKey,
                               nil];

AVAsset * movieAsset = [AVAsset assetWithURL:inputPath];
self.reader = [[AVAssetReader alloc] initWithAsset:movieAsset error:nil]; 

NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], (id)kCVPixelBufferPixelFormatTypeKey,nil];
self.frameOutput= [[AVAssetReaderTrackOutput alloc] initWithTrack:[[movieAsset tracks] objectAtIndex:0] outputSettings:outputSettings];

if([self.reader canAddOutput:self.frameOutput]){
    [self.reader addOutput:self.frameOutput];
}


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

channelLayout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;

NSDictionary *audioSettings =[NSDictionary dictionaryWithObjectsAndKeys:    [NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey,     [NSNumber numberWithFloat:44100.0], 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];

NSArray * audioTracks = [movieAsset tracksWithMediaType:AVMediaTypeAudio];
self.audioOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:[audioTracks lastObject] outputSettings:nil];

if([self.reader canAddOutput:self.audioOutput]){
    NSLog(@"ADDED");
    [self.reader addOutput:self.audioOutput];
}



self.writer = [[AVAssetWriter alloc] initWithURL:outputPath fileType:AVFileTypeQuickTimeMovie error:nil];    
self.writerInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
self.writerInput.expectsMediaDataInRealTime = YES;
[self.writerInput setTransform:CGAffineTransformMakeRotation(M_PI_2)];

self.audioWriterInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeAudio outputSettings:audioSettings];    
self.audioWriterInput.expectsMediaDataInRealTime = YES;   

[self.writer addInput:self.audioWriterInput];
[self.writer addInput:self.writerInput];

self.adaptor = [AVAssetWriterInputPixelBufferAdaptor assetWriterInputPixelBufferAdaptorWithAssetWriterInput:self.writerInput sourcePixelBufferAttributes:nil];

}


-(void) finish:(bool) success{
    [self.writer finishWriting];
    if(success && [self.delegate respondsToSelector:@selector(didFinishWritingMovieAtUrl:sender:)]){
        dispatch_async(dispatch_get_main_queue(),^{
            [self.delegate didFinishWritingMovieAtUrl:self.writer.outputURL sender:self];
        });
    }

    if(!success && [self.delegate respondsToSelector:@selector(didFailToWriteMovieAtUrl:sender:)]){
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.delegate didFailToWriteMovieAtUrl:self.writer.outputURL sender:self];
        });
    }
}

-(void) processAudioUsingQueue{

        while([self.audioWriterInput isReadyForMoreMediaData]){
            CMSampleBufferRef audioBuffer;
            if (self.reader.status == AVAssetReaderStatusReading) {
                NSLog(@"A");
                audioBuffer = [self.audioOutput copyNextSampleBuffer];
                NSLog(@"B");
                bool result = [self.audioWriterInput appendSampleBuffer:audioBuffer];
                if(!result){
                    [self.audioWriterInput markAsFinished];
                    [self.reader cancelReading];
                    break;
                }
            }else{
                [self.audioWriterInput markAsFinished];
                break;
            }
        }
        [self finish:YES];
}


-(void) processFramesUsingQueue:(dispatch_queue_t) queue{
    [self.writerInput requestMediaDataWhenReadyOnQueue:queue usingBlock:^{
        while([self.writerInput isReadyForMoreMediaData]){
            CMSampleBufferRef sampleBuffer;
            if (self.reader.status == AVAssetReaderStatusReading && (sampleBuffer = [self.frameOutput copyNextSampleBuffer])) {
                bool result = [self renderFrame:sampleBuffer];
                if(!result){
                    [self.reader cancelReading];
                    break;
                }
            }else{

                [self.writerInput markAsFinished];
                switch(self.reader.status){
                    case AVAssetReaderStatusReading:
                        [self performSelectorOnMainThread:@selector(processAudioUsingQueue) withObject:nil waitUntilDone:YES];
                        break;
                    case AVAssetReaderStatusCompleted:
                        [self finish:YES];
                        break;
                    case AVAssetReaderStatusCancelled:
                    case AVAssetReaderStatusFailed:                        
                        [self finish:NO];
                        [self.writer cancelWriting];
                        break;
                }
                break;
            }
        }


    }];



}

-(void) beginProcessingMovieAtPath:(NSURL*) inputPath withOutputPath:(NSURL*) outputPath startingTimeStamp:(CMTime) startTime{
    if(!self.costumeViews || !self.costumeFrames) NSLog(@"Warning... missing parameters!");
    [self initializeAtPath:inputPath withOutputPath:outputPath];
    [self.reader startReading];
    [self.writer startWriting];
    self.startFrameTime = startTime;
    [self.writer startSessionAtSourceTime:self.startFrameTime];
    // start thread to pull video data:
    dispatch_queue_t processvideo = dispatch_queue_create("process_queue", NULL);
    [self processFramesUsingQueue:processvideo];
}