сценарий использования композиции видео в формате pip с использованием собственного композитора (avfoundation)

Question

Я следую примеру кода на

https://github.com/robovm/apple-ios-samples/tree/master/AVCustomEdit/AVCustomEdit

Сшивание видео и переход отлично работает.

Я хочу обновить код для реализации сценария использования видео в картинке (поддерживая использование дизайна APLCustomVideoCompositionInstruction). Я обновил класс двумя новыми функциями: setPassThroughTrackID () и setTransitionWithSourceTrackIDs ().

        - (void)setPassThroughTrackID:(CMPersistentTrackID)passthroughTrackID forTimeRange:(CMTimeRange)timeRange
        {
            _passthroughTrackID = passthroughTrackID;
            _requiredSourceTrackIDs = nil;
            _timeRange = timeRange;
            _containsTweening = FALSE;
            _enablePostProcessing = FALSE;
            return;
        }

        - (void)setTransitionWithSourceTrackIDs:(NSArray *)sourceTrackIDs forTimeRange:(CMTimeRange)timeRange
        {
            _requiredSourceTrackIDs = sourceTrackIDs;
            _passthroughTrackID = kCMPersistentTrackID_Invalid;
            _timeRange = timeRange;
            _containsTweening = TRUE;
            _enablePostProcessing = FALSE;
            return;
        }

Любые рекомендации по этому вопросу будут высоко оценены.

Вот пример кода для создания Инструкция по компоновке для обычной строчки:

        sourceClips = [[NSMutableArray alloc] initWithCapacity:count];
        // Here creating a list of AVAsset using URL.
        [sourceClips addObject:[AVAsset assetWithURL:pUrlString1]];
        [sourceClips addObject:[AVAsset assetWithURL:pUrlString2]];

        AVMutableComposition *composition = [AVMutableComposition composition];
        NSMutableArray* compositionVideoTracks = [NSMutableArray array];

        CMTimeRange *passThroughTimeRanges = (CMTimeRange*)alloca(sizeof(CMTimeRange) * 2);
        CMTimeRange *srcClipTimeRanges = (CMTimeRange*)alloca(sizeof(CMTimeRange) * 2);
        CMTime *dstClipTimeStamp = (CMTime*)alloca(sizeof(CMTimeRange) * 2);

        int clipID = 0;
        passThroughTimeRanges[clipID] = CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1));
        srcClipTimeRanges[clipID] = CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1));
        dstClipTimeStamp[clipID] = CMTimeMake(0, 1);

        AVMutableCompositionTrack* track = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionVideoTracks addObject:track];

        AVURLAsset *asset = [_clips objectAtIndex:clipID];
        AVAssetTrack *clipVideoTrack = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

        [compositionVideoTracks[clipID] insertTimeRange:srcClipTimeRanges[clipID] ofTrack:clipVideoTrack atTime:dstClipTimeStamp[clipID] error:&error];

        AVMutableCompositionTrack * track0 = compositionVideoTracks[clipID];
        APLCustomVideoCompositionInstruction *videoInstruction = [APLCustomVideoCompositionInstruction alloc];
        [videoInstruction setPassThroughTrackID:track0.trackID forTimeRange:passThroughTimeRanges[clipID]];

Для PIP я попытался дать одинаковый диапазон времени для 2-х видео дорожек, но вывод не был создан.

        sourceClips = [[NSMutableArray alloc] initWithCapacity:size];
        // Here I am adding AVAsset
        [sourceClips addObject:[AVAsset assetWithURL:pUrlString1]];
        [sourceClips addObject:[AVAsset assetWithURL:pUrlString2]];

        AVMutableComposition *composition = [AVMutableComposition composition];
        NSMutableArray* compositionVideoTracks = [NSMutableArray array];

        CMTimeRange *passThroughTimeRanges = (CMTimeRange*)alloca(sizeof(CMTimeRange) * 2);
        CMTimeRange *srcClipTimeRanges = (CMTimeRange*)alloca(sizeof(CMTimeRange) * 2);
        CMTime *dstClipTimeStamp = (CMTime*)alloca(sizeof(CMTimeRange) * 2);

        int clipID = 0;
        passThroughTimeRanges[clipID] = CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1));
        srcClipTimeRanges[clipID] = CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1));
        dstClipTimeStamp[clipID] = CMTimeMake(0, 1);

        AVMutableCompositionTrack* track = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
        [compositionVideoTracks addObject:track];

        AVURLAsset *asset = [sourceClips objectAtIndex:clipID];
        AVAssetTrack *clipVideoTrack1 = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

        [compositionVideoTracks[clipID] insertTimeRange:srcClipTimeRanges[clipID] ofTrack:clipVideoTrack1 atTime:dstClipTimeStamp[clipID] error:&error];

        AVMutableCompositionTrack * track0 = compositionVideoTracks[clipID];
        APLCustomVideoCompositionInstruction *videoInstruction = [APLCustomVideoCompositionInstruction alloc];

        // trying to add pip
        {
            clipID = 1;
            passThroughTimeRanges[clipID] = CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1));
            srcClipTimeRanges[clipID] = CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1));
            dstClipTimeStamp[clipID] = CMTimeMake(0, 1);

            AVMutableCompositionTrack* trackPip = [composition addMutableTrackWithMediaType:AVMediaTypeVideo preferredTrackID:kCMPersistentTrackID_Invalid];
            [compositionVideoTracks addObject:trackPip];
            AVURLAsset *asset = [sourceClips objectAtIndex:clipID];
            AVAssetTrack *clipVideoTrack2 = [[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0];

            [compositionVideoTracks[clipID] insertTimeRange:srcClipTimeRanges[clipID] ofTrack:clipVideoTrack2 atTime:dstClipTimeStamp[clipID] error:&error];

            AVMutableCompositionTrack * track1 = compositionVideoTracks[clipID];
        }
        videoInstruction.foregroundTrackID = track0.trackID;
        videoInstruction.backgroundTrackID = track1.trackID;
        [videoInstruction setTransitionWithSourceTrackIDs:@[[NSNumber numberWithInt:track0.trackID], [NSNumber numberWithInt:track1.trackID]] forTimeRange:CMTimeRangeMake(kCMTimeZero, CMTimeMake(4, 1))];