AVMutableComposition - Blank/Black frame between videos assets

Question

I'm currently trying to put 5 videos back to back using AVMutableComposition like so:

[mixComposition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset1.duration) ofAsset:asset1 atTime:[mixComposition duration] error:nil];
[mixComposition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset2.duration) ofAsset:asset2 atTime:[mixComposition duration] error:nil];
[mixComposition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset3.duration) ofAsset:asset3 atTime:[mixComposition duration] error:nil];
[mixComposition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset4.duration) ofAsset:asset4 atTime:[mixComposition duration] error:nil];
[mixComposition insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset5.duration) ofAsset:asset5 atTime:[mixComposition duration] error:nil];

I then use an AVAssetExportSession to export the video, which works however between each video I'm getting a blank/black frame which I need to remove. Has anyone had this problem before and if so did you manage to fix it?

Also, the blank frames aren't in the source video files.

Thanks in advance.

Answer 1

I had the same problem the other day.

If you got your assets(asset1, asset2, etc.) by exporting them from other asset which was created using again insertTimeRange, then it's the same case.

The problem is that when you export assets created using insertTimeRange, the export doesn't go correct, when you attach such videos black frames appear between them.

Try using "timeRange" option of the AVAssetExportSession, and cut the range you need from the main asset. Then your assets will attach correct.

Answer 2

I just met the same problem. Turn out the solution is using AVMutableCompositionTrack and compositing the video tracks, something like this.

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

[videoTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, asset.duration) ofTrack:[[asset tracksWithMediaType:AVMediaTypeVideo] objectAtIndex:0] atTime:composition.duration error:&error];

For the audio part I think you must add a separate track with AVMediaTypeAudio type.