Ios AVAssetReader/AVAssetWriter以不同分辨率连接mp4文件
我正在编写一个iPad应用程序，其中我需要加入不同分辨率的mp4文件。为此，我使用AVAssetReader读取mp4源文件，AVAssetWriter将这些源文件写入单个mp4输出文件 我曾尝试使用AVAssetExportSession，但我遇到的问题是，不同连接的文件之间存在黑框 我现在面临的问题是，一切似乎都正常，但AVAssetWriter的完成处理程序从未被调用 下面是我的选择器，它以mp4文件URL列表、单个输出文件URL和一个完成处理程序作为输入Ios AVAssetReader/AVAssetWriter以不同分辨率连接mp4文件,ios,objective-c,mp4,avassetwriter,avassetreader,Ios,Objective C,Mp4,Avassetwriter,Avassetreader,我正在编写一个iPad应用程序，其中我需要加入不同分辨率的mp4文件。为此，我使用AVAssetReader读取mp4源文件，AVAssetWriter将这些源文件写入单个mp4输出文件 我曾尝试使用AVAssetExportSession，但我遇到的问题是，不同连接的文件之间存在黑框 我现在面临的问题是，一切似乎都正常，但AVAssetWriter的完成处理程序从未被调用 下面是我的选择器，它以mp4文件URL列表、单个输出文件URL和一个完成处理程序作为输入 - (void)resizeAn
- (void)resizeAndJoinVideosAtURLs:(NSArray *)videoURLs toOutputURL:(NSURL *)outputURL withHandler:(void(^)(NSURL *fileURL))handler
{
/*
First step: create the writer and writer input
*/
NSError *error = nil;
self.videoAssetWriter = [[AVAssetWriter alloc] initWithURL:outputURL fileType:AVFileTypeMPEG4 error:&error];
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:AVVideoCodecH264, AVVideoCodecKey,[NSNumber numberWithInt:640], AVVideoWidthKey,[NSNumber numberWithInt:480], AVVideoHeightKey,nil];
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
videoWriterInput.expectsMediaDataInRealTime = NO;
if([self.videoAssetWriter canAddInput:videoWriterInput])
{
[self.videoAssetWriter addInput:videoWriterInput];
[self.videoAssetWriter startWriting];
[self.videoAssetWriter startSessionAtSourceTime:kCMTimeZero];
/*
Second step: for each video URL given create a reader and an reader input
*/
for(NSURL *videoURL in videoURLs)
{
NSLog(@"Processing file: %@",videoURL);
AVAsset *videoAsset = [[AVURLAsset alloc] initWithURL:videoURL options:nil];
AVAssetReader *videoAssetReader = [[AVAssetReader alloc] initWithAsset:videoAsset error:&error];
AVAssetTrack *videoAssetTrack = [videoAsset tracksWithMediaType:AVMediaTypeVideo].firstObject;
NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput *videoAssetTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoAssetTrack outputSettings:videoOptions];
videoAssetTrackOutput.alwaysCopiesSampleData = NO;
if([videoAssetReader canAddOutput:videoAssetTrackOutput])
{
[videoAssetReader addOutput:videoAssetTrackOutput];
[videoAssetReader startReading];
/*
Step three: copy the buffers from the reader to the writer
*/
while ([videoAssetReader status] == AVAssetReaderStatusReading)
{
if(![videoWriterInput isReadyForMoreMediaData]) continue;
CMSampleBufferRef buffer = [videoAssetTrackOutput copyNextSampleBuffer];
if(buffer)
{
[videoWriterInput appendSampleBuffer:buffer];
CFRelease(buffer);
}
}
} else NSLog(@"ERROR: %@",error);
}
[videoWriterInput markAsFinished];
} else NSLog(@"ERROR: %@",error);
__weak ClipBuilder *weakself = self;
[self.videoAssetWriter finishWritingWithCompletionHandler:^{
handler(outputURL);
weakself.videoAssetWriter = nil;
}];
}
有什么可以解释呢？这是我最终实现的解决方案，通过Avassetrader/AVAssetWriter的组合以不同的分辨率连接mp4文件
- (void)reencodeComposition:(AVComposition *)composition toMP4File:(NSURL *)mp4FileURL withCompletionHandler:(void (^)(void))handler
{
self.status = EncoderStatusEncoding;
/*
Create the asset writer to write the file on disk
*/
NSError *error = nil;
if([[NSFileManager defaultManager] fileExistsAtPath:mp4FileURL.path isDirectory:nil])
{
if(![[NSFileManager defaultManager] removeItemAtPath:mp4FileURL.path error:&error])
{
[self failWithError:error withCompletionHandler:handler];
return;
}
}
self.assetWriter = [[AVAssetWriter alloc] initWithURL:mp4FileURL fileType:AVFileTypeMPEG4 error:&error];
if(self.assetWriter)
{
/*
Get the audio and video track of the composition
*/
AVAssetTrack *videoAssetTrack = [composition tracksWithMediaType:AVMediaTypeVideo].firstObject;
AVAssetTrack *audioAssetTrack = [composition tracksWithMediaType:AVMediaTypeAudio].firstObject;
NSDictionary *videoSettings = @{AVVideoCodecKey:AVVideoCodecH264, AVVideoWidthKey:@(self.imageWidth), AVVideoHeightKey:@(self.imageHeight)};
/*
Add an input to be able to write the video in the file
*/
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
videoWriterInput.expectsMediaDataInRealTime = YES;
if([self.assetWriter canAddInput:videoWriterInput])
{
[self.assetWriter addInput:videoWriterInput];
/*
Add an input to be able to write the audio in the file
*/
// Use this only if you know the format
// CMFormatDescriptionRef audio_fmt_desc_ = nil;
//
// AudioStreamBasicDescription audioFormat;
// bzero(&audioFormat, sizeof(audioFormat));
// audioFormat.mSampleRate = 44100;
// audioFormat.mFormatID = kAudioFormatMPEG4AAC;
// audioFormat.mFramesPerPacket = 1024;
// audioFormat.mChannelsPerFrame = 2;
// int bytes_per_sample = sizeof(float);
// audioFormat.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagIsPacked;
//
// audioFormat.mBitsPerChannel = bytes_per_sample * 8;
// audioFormat.mBytesPerPacket = bytes_per_sample * 2;
// audioFormat.mBytesPerFrame = bytes_per_sample * 2;
//
// CMAudioFormatDescriptionCreate(kCFAllocatorDefault,&audioFormat,0,NULL,0,NULL,NULL,&audio_fmt_desc_);
//
// AVAssetWriterInput* audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:nil sourceFormatHint:audio_fmt_desc_];
//
// AVAssetWriterInput* audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:nil sourceFormatHint:((__bridge CMAudioFormatDescriptionRef)audioAssetTrack.formatDescriptions.firstObject)];
audioWriterInput.expectsMediaDataInRealTime = YES;
if([self.assetWriter canAddInput:audioWriterInput])
{
[self.assetWriter addInput:audioWriterInput];
[self.assetWriter startWriting];
[self.assetWriter startSessionAtSourceTime:kCMTimeZero];
/*
Create the asset reader to read the mp4 files on the disk
*/
AVAssetReader *assetReader = [[AVAssetReader alloc] initWithAsset:composition error:&error];
NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
/*
Add an output to be able to retrieve the video in the files
*/
AVAssetReaderTrackOutput *videoAssetTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoAssetTrack outputSettings:videoOptions];
videoAssetTrackOutput.alwaysCopiesSampleData = NO;
if([assetReader canAddOutput:videoAssetTrackOutput])
{
[assetReader addOutput:videoAssetTrackOutput];
/*
Add an output to be able to retrieve the video in the files
*/
AVAssetReaderTrackOutput *audioAssetTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:audioAssetTrack outputSettings:nil];
videoAssetTrackOutput.alwaysCopiesSampleData = NO;
if([assetReader canAddOutput:audioAssetTrackOutput])
{
[assetReader addOutput:audioAssetTrackOutput];
[assetReader startReading];
/*
Read the mp4 files until the end and copy them in the output file
*/
dispatch_group_t encodingGroup = dispatch_group_create();
dispatch_group_enter(encodingGroup);
[audioWriterInput requestMediaDataWhenReadyOnQueue:self.encodingQueue usingBlock:^{
while ([audioWriterInput isReadyForMoreMediaData])
{
CMSampleBufferRef nextSampleBuffer = [audioAssetTrackOutput copyNextSampleBuffer];
if (nextSampleBuffer)
{
[audioWriterInput appendSampleBuffer:nextSampleBuffer];
CFRelease(nextSampleBuffer);
}
else
{
[audioWriterInput markAsFinished];
dispatch_group_leave(encodingGroup);
break;
}
}
}];
dispatch_group_enter(encodingGroup);
[videoWriterInput requestMediaDataWhenReadyOnQueue:self.encodingQueue usingBlock:^{
while ([videoWriterInput isReadyForMoreMediaData])
{
CMSampleBufferRef nextSampleBuffer = [videoAssetTrackOutput copyNextSampleBuffer];
if (nextSampleBuffer)
{
[videoWriterInput appendSampleBuffer:nextSampleBuffer];
CFRelease(nextSampleBuffer);
}
else
{
[videoWriterInput markAsFinished];
dispatch_group_leave(encodingGroup);
break;
}
}
}];
dispatch_group_wait(encodingGroup, DISPATCH_TIME_FOREVER);
} else [self failWithError:error withCompletionHandler:handler];
} else [self failWithError:error withCompletionHandler:handler];
} else [self failWithError:error withCompletionHandler:handler];
} else [self failWithError:error withCompletionHandler:handler];
__weak Encoder *weakself = self;
[self.assetWriter finishWritingWithCompletionHandler:^{
self.status = EncoderStatusCompleted;
handler();
weakself.assetWriter = nil;
self.encodingQueue = nil;
}];
}
else [self failWithError:error withCompletionHandler:handler];
}
这个实现是针对我的项目的，但我最终不需要它。这里是我最终实现的解决方案，通过Avassetrader/AVAssetWriter的组合以不同的分辨率连接mp4文件
- (void)reencodeComposition:(AVComposition *)composition toMP4File:(NSURL *)mp4FileURL withCompletionHandler:(void (^)(void))handler
{
self.status = EncoderStatusEncoding;
/*
Create the asset writer to write the file on disk
*/
NSError *error = nil;
if([[NSFileManager defaultManager] fileExistsAtPath:mp4FileURL.path isDirectory:nil])
{
if(![[NSFileManager defaultManager] removeItemAtPath:mp4FileURL.path error:&error])
{
[self failWithError:error withCompletionHandler:handler];
return;
}
}
self.assetWriter = [[AVAssetWriter alloc] initWithURL:mp4FileURL fileType:AVFileTypeMPEG4 error:&error];
if(self.assetWriter)
{
/*
Get the audio and video track of the composition
*/
AVAssetTrack *videoAssetTrack = [composition tracksWithMediaType:AVMediaTypeVideo].firstObject;
AVAssetTrack *audioAssetTrack = [composition tracksWithMediaType:AVMediaTypeAudio].firstObject;
NSDictionary *videoSettings = @{AVVideoCodecKey:AVVideoCodecH264, AVVideoWidthKey:@(self.imageWidth), AVVideoHeightKey:@(self.imageHeight)};
/*
Add an input to be able to write the video in the file
*/
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];
videoWriterInput.expectsMediaDataInRealTime = YES;
if([self.assetWriter canAddInput:videoWriterInput])
{
[self.assetWriter addInput:videoWriterInput];
/*
Add an input to be able to write the audio in the file
*/
// Use this only if you know the format
// CMFormatDescriptionRef audio_fmt_desc_ = nil;
//
// AudioStreamBasicDescription audioFormat;
// bzero(&audioFormat, sizeof(audioFormat));
// audioFormat.mSampleRate = 44100;
// audioFormat.mFormatID = kAudioFormatMPEG4AAC;
// audioFormat.mFramesPerPacket = 1024;
// audioFormat.mChannelsPerFrame = 2;
// int bytes_per_sample = sizeof(float);
// audioFormat.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagIsPacked;
//
// audioFormat.mBitsPerChannel = bytes_per_sample * 8;
// audioFormat.mBytesPerPacket = bytes_per_sample * 2;
// audioFormat.mBytesPerFrame = bytes_per_sample * 2;
//
// CMAudioFormatDescriptionCreate(kCFAllocatorDefault,&audioFormat,0,NULL,0,NULL,NULL,&audio_fmt_desc_);
//
// AVAssetWriterInput* audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:nil sourceFormatHint:audio_fmt_desc_];
//
// AVAssetWriterInput* audioWriterInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeAudio outputSettings:nil sourceFormatHint:((__bridge CMAudioFormatDescriptionRef)audioAssetTrack.formatDescriptions.firstObject)];
audioWriterInput.expectsMediaDataInRealTime = YES;
if([self.assetWriter canAddInput:audioWriterInput])
{
[self.assetWriter addInput:audioWriterInput];
[self.assetWriter startWriting];
[self.assetWriter startSessionAtSourceTime:kCMTimeZero];
/*
Create the asset reader to read the mp4 files on the disk
*/
AVAssetReader *assetReader = [[AVAssetReader alloc] initWithAsset:composition error:&error];
NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_32BGRA] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
/*
Add an output to be able to retrieve the video in the files
*/
AVAssetReaderTrackOutput *videoAssetTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoAssetTrack outputSettings:videoOptions];
videoAssetTrackOutput.alwaysCopiesSampleData = NO;
if([assetReader canAddOutput:videoAssetTrackOutput])
{
[assetReader addOutput:videoAssetTrackOutput];
/*
Add an output to be able to retrieve the video in the files
*/
AVAssetReaderTrackOutput *audioAssetTrackOutput = [[AVAssetReaderTrackOutput alloc] initWithTrack:audioAssetTrack outputSettings:nil];
videoAssetTrackOutput.alwaysCopiesSampleData = NO;
if([assetReader canAddOutput:audioAssetTrackOutput])
{
[assetReader addOutput:audioAssetTrackOutput];
[assetReader startReading];
/*
Read the mp4 files until the end and copy them in the output file
*/
dispatch_group_t encodingGroup = dispatch_group_create();
dispatch_group_enter(encodingGroup);
[audioWriterInput requestMediaDataWhenReadyOnQueue:self.encodingQueue usingBlock:^{
while ([audioWriterInput isReadyForMoreMediaData])
{
CMSampleBufferRef nextSampleBuffer = [audioAssetTrackOutput copyNextSampleBuffer];
if (nextSampleBuffer)
{
[audioWriterInput appendSampleBuffer:nextSampleBuffer];
CFRelease(nextSampleBuffer);
}
else
{
[audioWriterInput markAsFinished];
dispatch_group_leave(encodingGroup);
break;
}
}
}];
dispatch_group_enter(encodingGroup);
[videoWriterInput requestMediaDataWhenReadyOnQueue:self.encodingQueue usingBlock:^{
while ([videoWriterInput isReadyForMoreMediaData])
{
CMSampleBufferRef nextSampleBuffer = [videoAssetTrackOutput copyNextSampleBuffer];
if (nextSampleBuffer)
{
[videoWriterInput appendSampleBuffer:nextSampleBuffer];
CFRelease(nextSampleBuffer);
}
else
{
[videoWriterInput markAsFinished];
dispatch_group_leave(encodingGroup);
break;
}
}
}];
dispatch_group_wait(encodingGroup, DISPATCH_TIME_FOREVER);
} else [self failWithError:error withCompletionHandler:handler];
} else [self failWithError:error withCompletionHandler:handler];
} else [self failWithError:error withCompletionHandler:handler];
} else [self failWithError:error withCompletionHandler:handler];
__weak Encoder *weakself = self;
[self.assetWriter finishWritingWithCompletionHandler:^{
self.status = EncoderStatusCompleted;
handler();
weakself.assetWriter = nil;
self.encodingQueue = nil;
}];
}
else [self failWithError:error withCompletionHandler:handler];
}
这个实现是为我的项目设计的，但我最终不需要它。嗨，你用这段代码真的帮我省了不少时间。但我有一个奇怪的问题：音频直到最后才被复制，不是所有的音频样本都被添加到输出视频中。你能猜出原因吗？非常感谢，我很乐意！这里的代码片段就是为了这个原因。不幸的是，这个问题可能由代码或文件的许多问题引起。没有看到他们，真的很难猜测。我建议在创建AVComposition时检查音频格式、时间范围和使用的任何持续时间。谢谢你的回复。我正在使用您的代码，但奇怪的是，
[audioWriterInput isReadyForMoreMediaData]NO[AudioWriterInputRequestMediaDataWhenRepayonQueue:self.encodingQueue usingBlock:^{[audioWriterInput isReadyForMoreMediaData]否[AudioWriterInputRequestMediaDataWhenReadyonQueue:self.encodingQueue usingBlock:^{