AVFoundation + AssetWriter：生成带有图像和音频的电影

Question

我必须从我的 iPhone 应用程序中导出一部电影，其中包含来自 NSArray 的 UIImage，并添加一些 .caf 格式的音频文件，这些文件必须在预先指定的时间开始。 现在我已经能够使用 AVAssetWriter（在此站点和其他站点上浏览了许多问题和答案之后）导出包含图像的视频部分，但似乎无法找到添加音频文件以完成电影的方法。

这是我目前得到的结果

-(void) writeImagesToMovieAtPath:(NSString *) path withSize:(CGSize) size
{
    NSLog(@"Write Started");

    NSError *error = nil;

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

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

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


    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;

    for(UIImage * img in imageArray)
    {
            buffer = [self pixelBufferFromCGImage:[img CGImage] andSize:size];

            BOOL append_ok = NO;
            int j = 0;
            while (!append_ok && j < 30) 
            {
                if (adaptor.assetWriterInput.readyForMoreMediaData) 
                {
                    printf("appending %d attemp %d\n", frameCount, j);

                    CMTime frameTime = CMTimeMake(frameCount,(int32_t) kRecordingFPS);
                    append_ok = [adaptor appendPixelBuffer:buffer withPresentationTime:frameTime];

                    if(buffer)
                        CVBufferRelease(buffer);
                    [NSThread sleepForTimeInterval:0.05];
                } 
                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", frameCount, j);
            }
            frameCount++;
        }
    }

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

现在是 pixelBufferFromCGImage 的代码

- (CVPixelBufferRef) pixelBufferFromCGImage: (CGImageRef) image andSize:(CGSize) size
{
    NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:
                         [NSNumber numberWithBool:YES], kCVPixelBufferCGImageCompatibilityKey,
                         [NSNumber numberWithBool:YES], kCVPixelBufferCGBitmapContextCompatibilityKey,
                         nil];
    CVPixelBufferRef pxbuffer = NULL;

    CVReturn status = CVPixelBufferCreate(kCFAllocatorDefault, size.width,
                                      size.height, kCVPixelFormatType_32ARGB, (CFDictionaryRef) options, 
                                      &pxbuffer);
    NSParameterAssert(status == kCVReturnSuccess && pxbuffer != NULL);

    CVPixelBufferLockBaseAddress(pxbuffer, 0);
    void *pxdata = CVPixelBufferGetBaseAddress(pxbuffer);
    NSParameterAssert(pxdata != NULL);

    CGColorSpaceRef rgbColorSpace = CGColorSpaceCreateDeviceRGB();
    CGContextRef context = CGBitmapContextCreate(pxdata, size.width,
                                             size.height, 8, 4*size.width, rgbColorSpace, 
                                             kCGImageAlphaNoneSkipFirst);
    NSParameterAssert(context);
    CGContextConcatCTM(context, CGAffineTransformMakeRotation(0));
    CGContextDrawImage(context, CGRectMake(0, 0, CGImageGetWidth(image), 
                                           CGImageGetHeight(image)), image);
    CGColorSpaceRelease(rgbColorSpace);
    CGContextRelease(context);

    CVPixelBufferUnlockBaseAddress(pxbuffer, 0);

    return pxbuffer;
}

那么你能帮我解决一下如何添加音频文件以及如何为它们制作缓冲区以及适配器和输入设置等

如果这种方法可能会导致问题，请指导我如何使用 AVMutableComposition 将图像数组用于视频导出

Answer 1

我最终使用上述代码单独导出了视频，并使用 AVComposition 和 AVExportSession 分别添加了音频文件。 这是代码

-(void) addAudioToFileAtPath:(NSString *) filePath toPath:(NSString *)outFilePath
{
    NSError * error = nil;

    AVMutableComposition * composition = [AVMutableComposition composition];


    AVURLAsset * videoAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:filePath] options:nil];

    AVAssetTrack * videoAssetTrack = [[videoAsset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

    AVMutableCompositionTrack *compositionVideoTrack = [composition addMutableTrackWithMediaType:AVMediaTypeVideo 
                                                                                preferredTrackID: kCMPersistentTrackID_Invalid];

    [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,videoAsset.duration) ofTrack:videoAssetTrack atTime:kCMTimeZero
                                     error:&error];     

    CMTime audioStartTime = kCMTimeZero;
    for (NSDictionary * audioInfo in audioInfoArray)
    {
        NSString * pathString = [audioInfo objectForKey:audioFilePath];
        AVURLAsset * urlAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:pathString] options:nil];

        AVAssetTrack * audioAssetTrack = [[urlAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
        AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio 
                                                                                    preferredTrackID: kCMPersistentTrackID_Invalid];

        [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,urlAsset.duration) ofTrack:audioAssetTrack atTime:audioStartTime error:&error];      

        audioStartTime = CMTimeAdd(audioStartTime, CMTimeMake((int) (([[audioInfo objectForKey:audioDuration] floatValue] * kRecordingFPS) + 0.5), kRecordingFPS));
    }
    AVAssetExportSession* assetExport = [[AVAssetExportSession alloc] initWithAsset:composition presetName:AVAssetExportPresetMediumQuality];  
    assetExport.videoComposition = mutableVideoComposition;

    assetExport.outputFileType =AVFileTypeQuickTimeMovie;// @"com.apple.quicktime-movie";
    assetExport.outputURL = [NSURL fileURLWithPath:outFilePath];

    [assetExport exportAsynchronouslyWithCompletionHandler:
     ^(void ) {
         switch (assetExport.status) 
         {
             case AVAssetExportSessionStatusCompleted:
//                export complete 
                 NSLog(@"Export Complete");
                 break;
             case AVAssetExportSessionStatusFailed:
                 NSLog(@"Export Failed");
                 NSLog(@"ExportSessionError: %@", [assetExport.error localizedDescription]);
//                export error (see exportSession.error)  
                 break;
             case AVAssetExportSessionStatusCancelled:
                 NSLog(@"Export Failed");
                 NSLog(@"ExportSessionError: %@", [assetExport.error localizedDescription]);
//                export cancelled  
                 break;
         }
     }];    
}

Answer 2

您能否将“for”循环替换为单个“audioInfo”字典，该字典包含所有需要设置的值，以使其对复制粘贴更加友好？ :)

如果你只想添加一个音频文件，下面的代码应该替换 for 循环：

NSString * pathString = [self getAudioFilePath];
AVURLAsset * urlAsset = [AVURLAsset URLAssetWithURL:[NSURL fileURLWithPath:pathString] options:nil];

AVAssetTrack * audioAssetTrack = [[urlAsset tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVMutableCompositionTrack *compositionAudioTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio 
                                                    preferredTrackID: kCMPersistentTrackID_Invalid];

[compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero,urlAsset.duration) ofTrack:audioAssetTrack atTime:kCMTimeZero error:&error];