ReaderAndWriterAsset

AVFoundation AVAssetReader和AVAssetWriter AVAsset *asset = [AVAsset assetWithURL:[NSURL fileURLWithPath:path]]; NSError *error; //创建AVAssetReader对象用来读取asset数据 assetReader = [AVAssetReader assetReaderWithAsset:asset error:&error]; AVAsset *localAsset = assetReader.asset;

AVAssetTrack *videoTrack = [[localAsset tracksWithMediaType:AVMediaTypeVideo] firstObject];
AVAssetTrack *audioTrack = [[localAsset tracksWithMediaType:AVMediaTypeAudio] firstObject];

NSDictionary *videoSetting = @{(id)kCVPixelBufferPixelFormatTypeKey     : [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA],
                               (id)kCVPixelBufferIOSurfacePropertiesKey : [NSDictionary dictionary],
                               };

// AVAssetReaderTrackOutput用来设置怎么读数据 readerVideoTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:videoSetting]; //音频以pcm流的形似读数据 NSDictionary *audioSetting = @{AVFormatIDKey : [NSNumber numberWithUnsignedInt:kAudioFormatLinearPCM]}; readerAudioTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:audioTrack outputSettings:audioSetting];

if ([assetReader canAddOutput:readerVideoTrackOutput]) {
    [assetReader addOutput:readerVideoTrackOutput];
}

if ([assetReader canAddOutput:readerAudioTrackOutput]) {
    [assetReader addOutput:readerAudioTrackOutput];
}
//开始读
[assetReader startReading];

NSURL *writerUrl = [NSURL fileURLWithPath:writerPath];
//创建一个写数据对象
assetWriter = [[AVAssetWriter alloc] initWithURL:writerUrl fileType:AVFileTypeMPEG4 error:nil];
//配置写数据，设置比特率，帧率等
NSDictionary *compressionProperties = @{ AVVideoAverageBitRateKey : @(1.38*1024*1024),
                                         AVVideoExpectedSourceFrameRateKey: @(30),
                                         AVVideoProfileLevelKey : AVVideoProfileLevelH264HighAutoLevel };
//配置编码器宽高等
NSDictionary *compressionVideoSetting = @{
                          AVVideoCodecKey                   : AVVideoCodecTypeH264,
                          AVVideoWidthKey                   : @1080,
                          AVVideoHeightKey                  : @1080,
                          AVVideoCompressionPropertiesKey   : compressionProperties
                          };

AudioChannelLayout stereoChannelLayout = {
    .mChannelLayoutTag = kAudioChannelLayoutTag_Stereo,
    .mChannelBitmap = 0,
    .mNumberChannelDescriptions = 0
};
NSData *channelLayoutAsData = [NSData dataWithBytes:&stereoChannelLayout length:offsetof(AudioChannelLayout, mChannelDescriptions)];
//写入音频配置
NSDictionary *compressionAudioSetting = @{
                                           AVFormatIDKey         : [NSNumber numberWithUnsignedInt:kAudioFormatMPEG4AAC],
                                           AVEncoderBitRateKey   : [NSNumber numberWithInteger:64000],
                                           AVSampleRateKey       : [NSNumber numberWithInteger:44100],
                                           AVChannelLayoutKey    : channelLayoutAsData,
                                           AVNumberOfChannelsKey : [NSNumber numberWithUnsignedInteger:2]
                                           };
//AVAssetWriterInput用来说明怎么写数据
assetVideoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:compressionVideoSetting];
assetAudioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:compressionAudioSetting];

if ([assetWriter canAddInput:assetVideoWriterInput]) {
    [assetWriter addInput:assetVideoWriterInput];
}
if ([assetWriter canAddInput:assetAudioWriterInput]) {
    [assetWriter addInput:assetAudioWriterInput];
}
//开始写
[assetWriter startWriting];
[assetWriter startSessionAtSourceTime:kCMTimeZero];
dispatch_group_t group = dispatch_group_create();
dispatch_queue_t videoWriter = dispatch_queue_create("videoWriter", DISPATCH_QUEUE_CONCURRENT);
dispatch_queue_t audioWriter = dispatch_queue_create("audioWriter", DISPATCH_QUEUE_CONCURRENT);
__block BOOL isVideoComplete = NO;
dispatch_group_enter(group);
//要想写数据，就带有数据源，以下是将readerVideoTrackOutput读出来的数据加入到assetVideoWriterInput中再写入本地，音频和视频读取写入方式一样
[assetVideoWriterInput requestMediaDataWhenReadyOnQueue:videoWriter usingBlock:^{
    while (!isVideoComplete && assetVideoWriterInput.isReadyForMoreMediaData) {
        //样本数据
        @autoreleasepool {
            //每次读取一个buffer
            CMSampleBufferRef buffer = [readerVideoTrackOutput copyNextSampleBuffer];
            if (buffer) {
                //将读来的buffer加入到写对象中开始写
                //此处也可以给assetVideoWriterInput加个适配器对象可以写入CVPixelBuffer
                [assetVideoWriterInput appendSampleBuffer:buffer];
                //将buffer生成图片
                UIImage *image = [self imageFromSampleBuffer:buffer];
                //给图片添加滤镜
                UIImage *img = [self imageAddFilter:image];
                dispatch_async(dispatch_get_main_queue(), ^{
                    self.imageView.image = img;
                });
                CFRelease(buffer);
                buffer = NULL;
            } else {
                isVideoComplete = YES;
            }
        }
        
    }
    if (isVideoComplete) {
        //关闭写入会话
        [assetVideoWriterInput markAsFinished];
        dispatch_group_leave(group);
    }
}];