Ios AVAssetExportSession忽略视频合成旋转&；剥离元数据

我试图在上传到iOS设备之前旋转视频，因为其他平台（如android）无法正确解释iOS录制视频中的旋转信息，因此无法正确旋转播放

我查看了以下堆栈帖子，但没有成功地将它们应用到我的案例中：

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我处理了项目示例，但不幸的是，在创建AVAssetExportSession并调用exportAsynchronouslyWithCompletionHandler时，没有执行旋转，更糟糕的是，旋转元数据从结果文件中剥离

以下是运行导出的代码：

AVAssetExportSession *exportSession = [[AVAssetExportSession alloc] initWithAsset:[_mutableComposition copy] presetName:AVAssetExportPresetPassthrough];
exportSession.outputURL = outputURL;
exportSession.outputFileType = AVFileType3GPP;
exportSession.shouldOptimizeForNetworkUse = YES;
exportSession.videoComposition = _mutableVideoComposition;

[exportSession exportAsynchronouslyWithCompletionHandler:^(void)
 {
     NSLog(@"Status is %d %@", exportSession.status, exportSession.error);

     handler(exportSession);
     [exportSession release];
 }];

值_mutableComposition和_mutableVideoComposition通过以下方法初始化：

- (void) getVideoComposition:(AVAsset*)asset
{

    AVMutableComposition *mutableComposition = nil;
    AVMutableVideoComposition *mutableVideoComposition = nil;

    AVMutableVideoCompositionInstruction *instruction = nil;
    AVMutableVideoCompositionLayerInstruction *layerInstruction = nil;
    CGAffineTransform t1;
    CGAffineTransform t2;

    AVAssetTrack *assetVideoTrack = nil;
    AVAssetTrack *assetAudioTrack = nil;
    // Check if the asset contains video and audio tracks
    if ([[asset tracksWithMediaType:AVMediaTypeVideo] count] != 0) {
        assetVideoTrack = [asset tracksWithMediaType:AVMediaTypeVideo][0];
    }
    if ([[asset tracksWithMediaType:AVMediaTypeAudio] count] != 0) {
        assetAudioTrack = [asset tracksWithMediaType:AVMediaTypeAudio][0];
    }

    CMTime insertionPoint = kCMTimeZero;
    NSError *error = nil;


    // Step 1
    // Create a composition with the given asset and insert audio and video tracks into it from the asset
    // Check whether a composition has already been created, i.e, some other tool has already been applied
    // Create a new composition
    mutableComposition = [AVMutableComposition composition];

    // Insert the video and audio tracks from AVAsset
    if (assetVideoTrack != nil) {
        AVMutableCompositionTrack *compositionVideoTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionVideoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetVideoTrack atTime:insertionPoint error:&error];
    }
    if (assetAudioTrack != nil) {
        AVMutableCompositionTrack *compositionAudioTrack = [mutableComposition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionAudioTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, [asset duration]) ofTrack:assetAudioTrack atTime:insertionPoint error:&error];
    }


    // Step 2
    // Translate the composition to compensate the movement caused by rotation (since rotation would cause it to move out of frame)
    t1 = CGAffineTransformMakeTranslation(assetVideoTrack.naturalSize.height, 0.0);
    // Rotate transformation
    t2 = CGAffineTransformRotate(t1, degreesToRadians(90.0));


    // Step 3
    // Set the appropriate render sizes and rotational transforms
    // Create a new video composition
    mutableVideoComposition = [AVMutableVideoComposition videoComposition];
    mutableVideoComposition.renderSize = CGSizeMake(assetVideoTrack.naturalSize.height,assetVideoTrack.naturalSize.width);
    mutableVideoComposition.frameDuration = CMTimeMake(1, 30);

    // The rotate transform is set on a layer instruction
    instruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
    instruction.timeRange = CMTimeRangeMake(kCMTimeZero, [mutableComposition duration]);
    layerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:(mutableComposition.tracks)[0]];
    [layerInstruction setTransform:t2 atTime:kCMTimeZero];


    // Step 4
    // Add the transform instructions to the video composition
    instruction.layerInstructions = @[layerInstruction];
    mutableVideoComposition.instructions = @[instruction];

    TT_RELEASE_SAFELY(_mutableComposition);
    _mutableComposition = [mutableComposition retain];
    TT_RELEASE_SAFELY(_mutableVideoComposition);
    _mutableVideoComposition = [mutableVideoComposition retain];
}

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我从avserotate命令中提取了此方法。有人能提出为什么这种方法不能成功地将我的视频旋转90度吗

因为您使用的是

AVAssetExportPresetPassthrough

，

AVAssetExportSession

将忽略

视频合成

，所以请使用任何其他预设。

我遇到了与您相同的问题，下面建议的答案（例如更改为AVAssetExportPresetMediumQuality）无法解决问题。我也尝试在layerInstruction上添加setOpacity:0，但导出电影时似乎忽略了这些说明。我也有同样的问题，你有什么解决方案吗？这似乎不再有任何区别。你在模拟器中尝试吗？试用装置