如何使用 AVAssetWriter 将 h264 strem 写入视频？

Question

我想将 h.264 流从服务器制作成视频文件，但是当我使用 assetwrite.finishwrite 时，XCode 会报告

Video /var/mobile/Applications/DE4196F1-BB77-4B7D-8C20-7A5D6223C64D/Documents/test.mov cannot be saved to the saved photos album: Error Domain=NSOSStatusErrorDomain Code=-12847 "This movie format is not supported." UserInfo=0x5334830 {NSLocalizedDescription=This movie format is not supported.}"

以下是我的代码： data 是 h.264 帧，只有一帧，可能是 i 帧或 p。

(void)_encodeVideoFrame2:(NSData *) data time:(double)tm 
{
  CMBlockBufferRef videoBlockBuffer=NULL;
  CMFormatDescriptionRef videoFormat=NULL;
  CMSampleBufferRef videoSampleBuffer=NULL;
  CMItemCount numberOfSampleTimeEntries=1;
  CMItemCount numberOfSamples=1;
  CMVideoFormatDescriptionCreate(kCFAllocatorDefault, kCMVideoCodecType_H264, 320, 240, NULL, &videoFormat);
  OSStatus result;
  result=CMBlockBufferCreateWithMemoryBlock(kCFAllocatorDefault, NULL, data.length, kCFAllocatorDefault, NULL, 0, data.length, kCMBlockBufferAssureMemoryNowFlag, &videoBlockBuffer);
  result=CMBlockBufferReplaceDataBytes(data.bytes, videoBlockBuffer, 0, data.length);
  CMSampleTimingInfo videoSampleTimingInformation={CMTimeMake(tm*600, 600)};
  size_t sampleSizeArray[1];
  sampleSizeArray[0]=data.length;
  result=CMSampleBufferCreate(kCFAllocatorDefault, videoBlockBuffer, TRUE, NULL, NULL, videoFormat, numberOfSamples, numberOfSampleTimeEntries, &videoSampleTimingInformation, 1, sampleSizeArray, &videoSampleBuffer);
  result = CMSampleBufferMakeDataReady(videoSampleBuffer);
  [assetWriterInput appendSampleBuffer:videoSampleBuffer]; 
}

可能CMSampleBufferCreate 参数有误？谢谢。

Answer 1

试试这个代码

(IBAction)createVideo:(id)sender {

///////////// setup OR function def if we move this to a separate function ////////////
// this should be moved to its own function, that can take an imageArray, videoOutputPath, etc...
//    - (void)exportImages:(NSMutableArray *)imageArray
// asVideoToPath:(NSString *)videoOutputPath
// withFrameSize:(CGSize)imageSize
// framesPerSecond:(NSUInteger)fps {

NSError *error = nil;

// set up file manager, and file videoOutputPath, remove "test_output.mp4" if it exists...
//NSString *videoOutputPath = @"/Users/someuser/Desktop/test_output.mp4";
NSFileManager *fileMgr = [NSFileManager defaultManager];
NSString *documentsDirectory = [NSHomeDirectory()
                                stringByAppendingPathComponent:@"Documents"];
NSString *videoOutputPath = [documentsDirectory stringByAppendingPathComponent:@"test_output.mp4"];
//NSLog(@"-->videoOutputPath= %@", videoOutputPath);
// get rid of existing mp4 if exists...
if ([fileMgr removeItemAtPath:videoOutputPath error:&error] != YES)
    NSLog(@"Unable to delete file: %@", [error localizedDescription]);

CGSize imageSize = CGSizeMake(400, 200);
NSUInteger fps = 30;

//NSMutableArray *imageArray;
//imageArray = [[NSMutableArray alloc] initWithObjects:@"download.jpeg", @"download2.jpeg", nil];
NSMutableArray imageArray;
NSArray imagePaths = [[NSBundle mainBundle] pathsForResourcesOfType:@"jpg" inDirectory:nil];
imageArray = [[NSMutableArray alloc] initWithCapacity:imagePaths.count];
NSLog(@"-->imageArray.count= %i", imageArray.count);
for (NSString* path in imagePaths)
{
    [imageArray addObject:[UIImage imageWithContentsOfFile:path]];
    //NSLog(@"-->image path= %@", path);
}

//////////////     end setup    ///////////////////////////////////

NSLog(@"Start building video from defined frames.");

AVAssetWriter *videoWriter = [[AVAssetWriter alloc] initWithURL:
                              [NSURL fileURLWithPath:videoOutputPath] fileType:AVFileTypeQuickTimeMovie
                                                          error:&error];
NSParameterAssert(videoWriter);

NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               AVVideoCodecH264, AVVideoCodecKey,
                               [NSNumber numberWithInt:imageSize.width], AVVideoWidthKey,
                               [NSNumber numberWithInt:imageSize.height], AVVideoHeightKey,
                               nil];

AVAssetWriterInput* videoWriterInput = [AVAssetWriterInput
                                        assetWriterInputWithMediaType:AVMediaTypeVideo
                                        outputSettings:videoSettings];

AVAssetWriterInputPixelBufferAdaptor *adaptor = [AVAssetWriterInputPixelBufferAdaptor
                                                 assetWriterInputPixelBufferAdaptorWithAssetWriterInput:videoWriterInput
                                                 sourcePixelBufferAttributes:nil];

NSParameterAssert(videoWriterInput);
NSParameterAssert([videoWriter canAddInput:videoWriterInput]);
videoWriterInput.expectsMediaDataInRealTime = YES;
[videoWriter addInput:videoWriterInput];

//Start a session:
[videoWriter startWriting];
[videoWriter startSessionAtSourceTime:kCMTimeZero];

CVPixelBufferRef buffer = NULL;

//convert uiimage to CGImage.
int frameCount = 0;
double numberOfSecondsPerFrame = 6;
double frameDuration = fps * numberOfSecondsPerFrame;

//for(VideoFrame * frm in imageArray)
NSLog(@"****************************");
for(UIImage * img in imageArray)
{
    //UIImage * img = frm._imageFrame;
    buffer = [self pixelBufferFromCGImage:[img CGImage]];

BOOL append_ok = NO;
int j = 0;
while (!append_ok && j < 30) {
    if (adaptor.assetWriterInput.readyForMoreMediaData)  {
        //print out status:
        NSLog(@"Processing video frame (%d,%d)",frameCount,[imageArray count]);

        CMTime frameTime = CMTimeMake(frameCount*frameDuration,(int32_t) fps);
        append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];
        if(!append_ok){
            NSError *error = videoWriter.error;
            if(error!=nil) {
                NSLog(@"Unresolved error %@,%@.", error, [error userInfo]);
            }
        }
    }
    else {
        printf("adaptor not ready %d, %d\n", frameCount, j);
        [NSThread sleepForTimeInterval:0.1];
    }
    j++;
}
if (!append_ok) {
    printf("error appending image %d times %d\n, with error.", frameCount, j);
}
frameCount++;


}
NSLog(@"****************************");

//Finish the session:
[videoWriterInput markAsFinished];
[videoWriter finishWriting];
NSLog(@"Write Ended");

////////////////////////////////////////////////////////////////////////////
//////////////  OK now add an audio file to move file  /////////////////////
AVMutableComposition* mixComposition = [AVMutableComposition composition];

NSString *bundleDirectory = [[NSBundle mainBundle] bundlePath];
// audio input file...
NSString *audio_inputFilePath = [bundleDirectory stringByAppendingPathComponent:@"30secs.mp3"];
NSURL    *audio_inputFileUrl = [NSURL fileURLWithPath:audio_inputFilePath];

// this is the video file that was just written above, full path to file is in --> videoOutputPath
NSURL    *video_inputFileUrl = [NSURL fileURLWithPath:videoOutputPath];

// create the final video output file as MOV file - may need to be MP4, but this works so far...
NSString *outputFilePath = [documentsDirectory stringByAppendingPathComponent:@"final_video.mp4"];
NSURL    *outputFileUrl = [NSURL fileURLWithPath:outputFilePath];

if ([[NSFileManager defaultManager] fileExistsAtPath:outputFilePath])
    [[NSFileManager defaultManager] removeItemAtPath:outputFilePath error:nil];

CMTime nextClipStartTime = kCMTimeZero;

AVURLAsset* videoAsset = [[AVURLAsset alloc]initWithURL:video_inputFileUrl options:nil];
CMTimeRange video_timeRange = CMTimeRangeMake(kCMTimeZero,videoAsset.duration);
AVMutableCompositionTrack *a_compositionVideoTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
[a_compositionVideoTrack insertTimeRange:video_timeRange ofTrack:[[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:nextClipStartTime error:nil];

//nextClipStartTime = CMTimeAdd(nextClipStartTime, a_timeRange.duration);

AVURLAsset* audioAsset = [[AVURLAsset alloc]initWithURL:audio_inputFileUrl options:nil];
CMTimeRange audio_timeRange = CMTimeRangeMake(kCMTimeZero, audioAsset.duration);
AVMutableCompositionTrack *b_compositionAudioTrack = [mixComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
[b_compositionAudioTrack insertTimeRange:audio_timeRange ofTrack:[[audioAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0] atTime:nextClipStartTime error:nil];

//AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetHighestQuality];
__block AVAssetExportSession* _assetExport = [[AVAssetExportSession alloc] initWithAsset:mixComposition presetName:AVAssetExportPresetPassthrough];

NSLog(@"support file types= %@", [_assetExport supportedFileTypes]);
_assetExport.outputFileType = @"com.apple.quicktime-movie";
NSLog(@"support file types= %@", [_assetExport supportedFileTypes]);
_assetExport.outputURL = outputFileUrl;

[_assetExport exportAsynchronouslyWithCompletionHandler:^{
    switch (_assetExport.status) {
        case AVAssetExportSessionStatusCompleted:
            // Custom method to import the Exported Video
            NSLog(@"completed!!!");
            break;
        case AVAssetExportSessionStatusFailed:
            //
            NSLog(@"Failed:%@",_assetExport.error);
            break;
        case AVAssetExportSessionStatusCancelled:
            //
            NSLog(@"Canceled:%@",_assetExport.error);
            break;
        default:
            break;
    }
}];

///// THAT IS IT DONE... the final video file will be written here...
NSLog(@"DONE.....outputFilePath--->%@", outputFilePath);

// the final video file will be located somewhere like here:
// /Users/caferrara/Library/Application Support/iPhone Simulator/6.0/Applications/D4B12FEE-E09C-4B12-B772-7F1BD6011BE1/Documents/outputFile.mov


}

Answer 2

为了将已压缩的 h264 缓冲区与 AVAssetWriter 混合，您必须指定 nil 输出设置，这与文档所述相反。

所以，不要这样做

videoInput = [[AVAssetWriterInput alloc] 
    initWithMediaType:AVMediaTypeVideo outputSettings:@{
        AVVideoCodecKey: AVVideoCodecH264,
    }
    sourceFormatHint:myVideoFormat
];

你应该这样做

videoInput = [[AVAssetWriterInput alloc] 
    initWithMediaType:AVMediaTypeVideo
    outputSettings:nil
    sourceFormatHint:myVideoFormat
];

这将使您能够传递视频或音频数据，而无需 AVAssetWriterInput 尝试为您编码/转码任何内容。