我尝试将多个视频文件合并到一个具有特定编解码器设置的文件中。我过去常常使用AVAssetExportSession，但我现在需要比AVAssetExportSession提供更多的编解码器控制权。
下面我发布了处理视频文件组合的createFinalVideo:功能。
我采用的方法是尝试使用AVAssetWriter写入同一文件，同时只需在应添加下一个视频的位置启动会话。我知道这不起作用，因为AVAssetWriter显然不允许这种行为。
以前，我在for循环之外定义了AVAssetWriter，我试图为每个视频文件添加一个新输入（for循环的每次传递）。但是，AVAssetWriter似乎不允许在调用[AVAssetWriter startWriting]后添加新输入。
我的问题是我如何做正确的尝试？
/**
* Final video creation. Merges audio-only and video-only files.
**/
-(void)createFinalVideo:(id)args
{
ENSURE_SINGLE_ARG(args, NSDictionary);
// presentation id
NSString * presID = [args objectForKey:@"presID"];
// array of video paths
NSArray * videoPathsArray = [args objectForKey:@"videoPaths"];
videoSuccessCallback = [args objectForKey:@"videoSuccess"];
videoCancelCallback = [args objectForKey:@"videoCancel"];
videoErrorCallback = [args objectForKey:@"videoError"];
NSError * error = nil;
NSFileManager * fileMgr = [NSFileManager defaultManager];
NSString * bundleDirectory = [[NSBundle mainBundle] bundlePath];
NSString * documentsDirectory = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];
/*********************************************************************/
/* BEGIN: merge all videos into a final MP4 */
/*********************************************************************/
// create the final video output file as MP4 file
NSString * finalOutputFilePath = [NSString stringWithFormat:@"%@/%@/final_video.mp4", documentsDirectory, presID];
NSURL * finalOutputFileUrl = [NSURL fileURLWithPath:finalOutputFilePath];
// delete file if it exists
if ([fileMgr fileExistsAtPath:finalOutputFilePath]) {
[fileMgr removeItemAtPath:finalOutputFilePath error:nil];
}
float renderWidth = 640, renderHeight = 480;
NSDictionary *videoCleanApertureSettings = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:renderWidth], AVVideoCleanApertureWidthKey,
[NSNumber numberWithInt:renderHeight], AVVideoCleanApertureHeightKey,
[NSNumber numberWithInt:10], AVVideoCleanApertureHorizontalOffsetKey,
[NSNumber numberWithInt:10], AVVideoCleanApertureVerticalOffsetKey,
nil];
NSDictionary *codecSettings = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:1960000], AVVideoAverageBitRateKey,
[NSNumber numberWithInt:24],AVVideoMaxKeyFrameIntervalKey,
videoCleanApertureSettings, AVVideoCleanApertureKey,
AVVideoProfileLevelH264Baseline30, AVVideoProfileLevelKey,
nil];
NSDictionary *videoCompressionSettings = [NSDictionary dictionaryWithObjectsAndKeys:
AVVideoCodecH264, AVVideoCodecKey,
codecSettings,AVVideoCompressionPropertiesKey,
[NSNumber numberWithInt:renderWidth], AVVideoWidthKey,
[NSNumber numberWithInt:renderHeight], AVVideoHeightKey,
AVVideoScalingModeResizeAspect, AVVideoScalingModeKey,
nil];
NSError *aerror = nil;
// next start time for adding to the compositions
CMTime nextStartTime = kCMTimeZero;
// loop through the video paths and add videos to the composition
for (NSString * path in videoPathsArray) {
// wait for each video to finish writing before continuing
dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
// create video writer
AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:finalOutputFileUrl fileType:AVFileTypeQuickTimeMovie error:nil];
NSParameterAssert(videoWriter);
NSLog(@"at the top of the for loop");
NSLog(@"%@", path);
AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeVideo
outputSettings:videoCompressionSettings];
NSParameterAssert(videoWriterInput);
NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
videoWriterInput.expectsMediaDataInRealTime = YES;
[videoWriter addInput:videoWriterInput];
AVAssetWriterInput* audioWriterInput = [AVAssetWriterInput
assetWriterInputWithMediaType:AVMediaTypeAudio
outputSettings:nil];
NSParameterAssert(audioWriterInput);
NSParameterAssert([videoWriter canAddInput:audioWriterInput]);
audioWriterInput.expectsMediaDataInRealTime = NO;
[videoWriter addInput:audioWriterInput];
[videoWriter startWriting];
// video setup
AVAsset *avAsset = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:path] options:nil];
AVAssetReader *reader = [[AVAssetReader alloc] initWithAsset:avAsset error:&aerror];
AVAssetTrack *videoTrack = [[avAsset tracksWithMediaType:AVMediaTypeVideo]objectAtIndex:0];
CMTime videoDuration = avAsset.duration;
// Wait until the duration is actually available
int durationAttempts = 5;
while(CMTimeGetSeconds(videoDuration) == 0 && durationAttempts > 0) {
durationAttempts--;
[NSThread sleepForTimeInterval:0.3];
videoDuration = avAsset.duration;
}
NSLog(@"[INFO] MODULE-VIDUTILS video duration in secs: %f", CMTimeGetSeconds(videoDuration));
//videoWriterInput.transform = videoTrack.preferredTransform;
NSDictionary *videoOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithInt:kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange] forKey:(id)kCVPixelBufferPixelFormatTypeKey];
AVAssetReaderTrackOutput *asset_reader_output = [[AVAssetReaderTrackOutput alloc] initWithTrack:videoTrack outputSettings:videoOptions];
[reader addOutput:asset_reader_output];
//audio setup
AVAssetReader *audioReader = [AVAssetReader assetReaderWithAsset:avAsset error:nil];
AVAssetTrack* audioTrack = [[avAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVAssetReaderOutput *readerOutput = [AVAssetReaderTrackOutput assetReaderTrackOutputWithTrack:audioTrack outputSettings:nil];
[audioReader addOutput:readerOutput];
NSLog(@"startSessionAtSourceTime: %f", CMTimeGetSeconds(nextStartTime));
[videoWriter startSessionAtSourceTime:nextStartTime];
// set next start time
nextStartTime = CMTimeAdd(nextStartTime, videoDuration);
[reader startReading];
dispatch_queue_t _processingQueue = dispatch_queue_create("AVAssetWriterQueue", DISPATCH_QUEUE_SERIAL);
[videoWriterInput requestMediaDataWhenReadyOnQueue:_processingQueue usingBlock:^{
while ([videoWriterInput isReadyForMoreMediaData]) {
CMSampleBufferRef sampleBuffer;
if ([reader status] == AVAssetReaderStatusReading &&
(sampleBuffer = [asset_reader_output copyNextSampleBuffer])) {
BOOL result = [videoWriterInput appendSampleBuffer:sampleBuffer];
CFRelease(sampleBuffer);
if (!result) {
[reader cancelReading];
NSLog(@"NO RESULT");
NSLog (@"[INFO] MODULE-VIDUTILS createFinalVideo AVAssetWriterInputStatusFailed: %@", videoWriter.error);
if (videoErrorCallback != nil) {
[self _fireEventToListener:@"videoError" withObject:nil listener:videoErrorCallback thisObject:nil];
}
return;
break;
}
} else {
[videoWriterInput markAsFinished];
switch ([reader status]) {
case AVAssetReaderStatusReading:
// the reader has more for other tracks, even if this one is done
break;
case AVAssetReaderStatusCompleted:
[audioReader startReading];
[videoWriter startSessionAtSourceTime:nextStartTime];
NSLog(@"Request");
NSLog(@"Asset Writer ready :%d", audioWriterInput.readyForMoreMediaData);
while (audioWriterInput.readyForMoreMediaData) {
CMSampleBufferRef nextBuffer;
if ([audioReader status] == AVAssetReaderStatusReading && (nextBuffer = [readerOutput copyNextSampleBuffer])) {
NSLog(@"Ready");
if (nextBuffer) {
NSLog(@"NextBuffer");
[audioWriterInput appendSampleBuffer:nextBuffer];
}
} else {
[audioWriterInput markAsFinished];
//dictionary to hold duration
if ([audioReader status] == AVAssetReaderStatusCompleted) {
NSLog (@"[INFO] MODULE-VIDUTILS createFinalVideo AVAssetReaderStatusCompleted");
[videoWriter finishWritingWithCompletionHandler:^{
switch([videoWriter status]) {
case AVAssetWriterStatusCompleted:
NSLog (@"[INFO] MODULE-VIDUTILS createFinalVideo AVAssetWriterStatusCompleted");
dispatch_semaphore_signal(semaphore);
break;
case AVAssetWriterStatusCancelled:
NSLog (@"[INFO] MODULE-VIDUTILS createFinalVideo AVAssetWriterStatusCancelled");
if (videoSuccessCallback != nil) {
[self _fireEventToListener:@"videoCancel" withObject:nil listener:videoCancelCallback thisObject:nil];
}
return;
break;
case AVAssetWriterStatusFailed:
NSLog (@"[INFO] MODULE-VIDUTILS createFinalVideo AVAssetWriterStatusFailed");
if (videoSuccessCallback != nil) {
[self _fireEventToListener:@"videoError" withObject:nil listener:videoErrorCallback thisObject:nil];
}
return;
break;
}
}];
break;
}
}
}
break;
case AVAssetReaderStatusFailed:
NSLog (@"[INFO] MODULE-VIDUTILS createFinalVideo AVAssetReaderStatusFailed, @%", reader.error);
if (videoSuccessCallback != nil) {
[self _fireEventToListener:@"videoError" withObject:nil listener:videoErrorCallback thisObject:nil];
}
[videoWriter cancelWriting];
return;
break;
}
break;
}
}
}];
// wait for the writing to finish
dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
NSLog(@"Write Ended");
}
NSLog(@"got here -- should have waited for all videos to complete first");
// call success if we got here
if (videoSuccessCallback != nil) {
[self _fireEventToListener:@"videoSuccess" withObject:nil listener:videoSuccessCallback thisObject:nil];
}
}