AVFoundation 教你如何处理混音，拼接，消音，快进倒放等功能！ 如果你对于AVfoundation如何处理视频数据,请先参考这篇文章
==> GitHub直通车(终于抽空把demo整理了一份发到了GitHub.demo如有出错可以联系我!)
通过上篇文章我们得到处理好的音视频轨，我们如何输出，把编辑好的数据写到文件中去呢？那么我们一般使用的是AVassetwriter和AVassetReader结合.我们处理音视轨之后会获得三个实例,分别为 AVMutableComposition AVMutableVideoComposition AVMutableAudioMix 拿到了这三个实例我们就要去创建AVAssetReader实例对象.
- (AVAssetReader*)createAssetReader:(AVComposition *)compositon
videoComposition:(AVVideoComposition *)videoComposition
audioMix:(AVAudioMix *)audioMix{
NSError *error = nil;
AVAssetReader *assetReader = [AVAssetReader assetReaderWithAsset:compositon error:&error];
assetReader.timeRange = CMTimeRangeMake(kCMTimeZero, CMTimeMake(compositon.duration.value, compositon.duration.timescale));
NSDictionary *outputSettings = @{(id)kCVPixelBufferPixelFormatTypeKey: @(kCVPixelFormatType_420YpCbCr8BiPlanarFullRange)};
AVAssetReaderVideoCompositionOutput *readerVideoOutput = [AVAssetReaderVideoCompositionOutput assetReaderVideoCompositionOutputWithVideoTracks:[compositon tracksWithMediaType:AVMediaTypeVideo]
videoSettings:outputSettings];
#if ! TARGET_IPHONE_SIMULATOR
if( [AVVideoComposition isKindOfClass:[AVMutableVideoComposition class]] )
[(AVMutableVideoComposition*)videoComposition setRenderScale:1.0];
#endif
readerVideoOutput.videoComposition = videoComposition;
readerVideoOutput.alwaysCopiesSampleData = NO;
[assetReader addOutput:readerVideoOutput];
NSArray *audioTracks = [compositon tracksWithMediaType:AVMediaTypeAudio];
BOOL shouldRecordAudioTrack = ([audioTracks count] > 0);//modify be Chen siyang 2017-04-08
AVAssetReaderAudioMixOutput *readerAudioOutput = nil;
if (shouldRecordAudioTrack)
{
readerAudioOutput = [AVAssetReaderAudioMixOutput assetReaderAudioMixOutputWithAudioTracks:audioTracks audioSettings:nil];
readerAudioOutput.audioMix = audioMix;
readerAudioOutput.alwaysCopiesSampleData = NO;
[assetReader addOutput:readerAudioOutput];
}
return assetReader;
}
AVAssetReaderTrackOutput
我们创建AVassetReader的方法里创建了两个AVAssetReaderTrackOutput 分别是AVAssetReaderVideoCompositionOutput 和 AVAssetReaderAudioMixOutput 两个实例,都是AVAssetReaderTrackOutput的子类.分别包含了 视频的输出和音频的输出.
我们也可以从 AVassetReader 中获取到这个变量
//获取输出音视频数据
AVAssetReaderTrackOutput *readerVideoTrackOutput = nil;
AVAssetReaderAudioMixOutput *readerAudioOutput = nil;
for( AVAssetReaderTrackOutput *output in assetReader.outputs ) {
if( [output.mediaType isEqualToString:AVMediaTypeVideo] ) {
readerVideoTrackOutput = output;
}
if ([output.mediaType isEqualToString:AVMediaTypeAudio]) {
readerAudioOutput = (AVAssetReaderAudioMixOutput *)output;
}
}
AVassetWriter
AVassetWriter 该类的作用是把 AVassetReader 的输出(AVAssetReaderTrackOutput) 通过回调 写成文件.
创建 AVassetWriter
//初始化avassetWriter
//输出地址
NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager removeItemAtURL:outPutUrl error:nil];
AVAssetWriter *assetWriter = [AVAssetWriter assetWriterWithURL:outPutUrl fileType:AVFileTypeQuickTimeMovie error:nil];
//音频
NSDictionary *audioInputSetting = [self configAudioInput];
//此处配置音频输入设置，audioInputSetting可以为nil，表示不经过处理
AVAssetWriterInput *audioTrackInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:audioInputSetting];
//视频
NSDictionary *videoInputSetting = [self configVideoInput] ;
//此处配置视频频输入设置，videoInputSetting可以为nil，表示不经过处理
AVAssetWriterInput *videoTrackInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoInputSetting];
if ([assetWriter canAddInput:audioTrackInput]) {
[assetWriter addInput:audioTrackInput];
}
if ([assetWriter canAddInput:videoTrackInput]) {
[assetWriter addInput:videoTrackInput];
}
这里对应的音视频InputSetting 是 对你写出的音视频格式的设置.如果你不设置,就会把数据全部写出来.是无损无压缩的,大小大概会比一般的MP3格式 打1000倍.
编码设置
音频编码
/**
编码音频
@return 返回编码字典
*/
- (NSDictionary *)configAudioInput{
AudioChannelLayout channelLayout = {
.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo,
.mChannelBitmap = kAudioChannelBit_Left,
.mNumberChannelDescriptions = 0
};
NSData *channelLayoutData = [NSData dataWithBytes:&channelLayout length:offsetof(AudioChannelLayout, mChannelDescriptions)];
NSDictionary *audioInputSetting = @{
AVFormatIDKey: @(kAudioFormatMPEG4AAC),
AVSampleRateKey: @(44100),
AVNumberOfChannelsKey: @(2),
AVChannelLayoutKey:channelLayoutData
};
return audioInputSetting;
}
视频编码
/**
编码视频
@return 返回编码字典
*/
- (NSDictionary *)configVideoInput{
NSDictionary *videoInputSetting = @{
AVVideoCodecKey:AVVideoCodecH264,
AVVideoWidthKey: @(374),
AVVideoHeightKey: @(666)
};
return videoInputSetting;
}
SampleBufferRef
到这里我们AVassetWriter和AVassetReader的设置都已经设置成功,就开始读和写了.
[assetReader startReading];
[assetWriter startWriting];
然后我们创建两个同步队列,同时解析音频和视频的outPut生成的sampleBufferRef
dispatch_queue_t rwAudioSerializationQueue = dispatch_queue_create("Audio Queue", DISPATCH_QUEUE_SERIAL);
dispatch_queue_t rwVideoSerializationQueue = dispatch_queue_create("Video Queue", DISPATCH_QUEUE_SERIAL);
dispatch_group_t dispatchGroup = dispatch_group_create();
//这里开始时间是可以自己设置的
[assetWriter startSessionAtSourceTime:kCMTimeZero];
dispatch_group_enter(dispatchGroup);
__block BOOL isAudioFirst = YES;
[assetWriterAudioInput requestMediaDataWhenReadyOnQueue:rwAudioSerializationQueue usingBlock:^{
while ([assetWriterAudioInput isReadyForMoreMediaData]&&assetReader.status == AVAssetReaderStatusReading) {
CMSampleBufferRef nextSampleBuffer = [assetReaderAudioOutput copyNextSampleBuffer];
if (isAudioFirst) {
isAudioFirst = !isAudioFirst;
continue;
}
if (nextSampleBuffer) {
[assetWriterAudioInput appendSampleBuffer:nextSampleBuffer];
CFRelease(nextSampleBuffer);
} else {
[assetWriterAudioInput markAsFinished];
dispatch_group_leave(dispatchGroup);
break;
}
}
}];
dispatch_group_enter(dispatchGroup);
__block BOOL isVideoFirst = YES;
[assetWriterVideoInput requestMediaDataWhenReadyOnQueue:rwVideoSerializationQueue usingBlock:^{
while ([assetWriterVideoInput isReadyForMoreMediaData]&&assetReader.status == AVAssetReaderStatusReading) {
CMSampleBufferRef nextSampleBuffer = [assetReaderVideoOutput copyNextSampleBuffer];
if (isVideoFirst) {
isVideoFirst = !isVideoFirst;
continue;
}
if (nextSampleBuffer) {
[assetWriterVideoInput appendSampleBuffer:nextSampleBuffer];
CFRelease(nextSampleBuffer);
NSLog(@"加载");
} else {
[assetWriterVideoInput markAsFinished];
dispatch_group_leave(dispatchGroup);
break;
}
}
}];
dispatch_group_notify(dispatchGroup, dispatch_get_main_queue(), ^{
[assetWriter finishWritingWithCompletionHandler:^{
if (assetWriter.status == AVAssetWriterStatusCompleted) {
NSLog(@"加载完毕");
} else {
NSLog(@"加载失败");
}
if ([self.delegate respondsToSelector:@selector(synthesisResult)]) {
[self.delegate synthesisResult];
}
}];
});
到这里我们的音视频的混音功能和保存就完成了.对于拼接 和 消音,快进和倒放就之后会抽时间也写出来.其实原理都在这了.demo 我后面再补!
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