ios - AVMutableComposition - 连接的视频 Assets 在第一个 Assets 后停止

Question

我正在使用以下代码连接多个 AVURLAssets:

AVMutableComposition * movie = [AVMutableComposition composition];

CMTime offset = kCMTimeZero;

for (AVURLAsset * asset in assets) {
    AVMutableCompositionTrack *compositionVideoTrack = [movie addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
    AVMutableCompositionTrack *compositionAudioTrack = [movie addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];

    AVAssetTrack *assetVideoTrack = [asset tracksWithMediaType:AVMediaTypeVideo].firstObject;
    AVAssetTrack *assetAudioTrack = [asset tracksWithMediaType:AVMediaTypeAudio].firstObject;

    CMTimeRange timeRange = CMTimeRangeMake(kCMTimeZero, asset.duration);
    NSError * error = nil;

    if (![compositionVideoTrack insertTimeRange: timeRange ofTrack: assetVideoTrack atTime: offset error: &error]) {
        NSLog(@"Error adding video track - %@", error);
    }
    if (![compositionAudioTrack insertTimeRange: timeRange ofTrack: assetAudioTrack atTime: offset error: &error]) {
        NSLog(@"Error adding audio track - %@", error);
    }

    offset = CMTimeAdd(offset, asset.duration);
}

生成的合成一直播放到所有原始 Assets 的组合持续时间，音频播放正确，但只有第一个 Assets 的视频播放，然后在其最后一帧暂停。

对我做错了什么有什么想法吗？

原始 Assets 的顺序无关紧要 - 第一个视频和所有音频播放。

Answer 1

您需要使用 AVVideoCompositionInstructions 的实例创建一个 AVVideoComposition。看看这个 sample code .

您感兴趣的代码应该是这种性质的:

AVMutableVideoCompositionLayerInstruction *videoCompositionLayerInstruction = [AVMutableVideoCompositionLayerInstruction videoCompositionLayerInstructionWithAssetTrack:mutableVideoTrack];
[self.layerInstructions addObject:videoCompositionLayerInstruction];
        AVMutableVideoCompositionInstruction *passThroughInstruction = [AVMutableVideoCompositionInstruction videoCompositionInstruction];
        passThroughInstruction.timeRange = trackTimeRange;
        passThroughInstruction.layerInstructions = @[videoCompositionLayerInstruction];
[self.compositionInstructions addObject:passThroughInstruction];