Avmutablevideocomposition Output Video Shrinked

exporting CALayer with AVMutableVideoComposition

yes I see the issue, thanks for the code BTW! I have been trying to do this, and I just copy paste (I'm a noob) but I found your issue while editing the code for my issue, this line

NSString *urlStr = [[NSBundle mainBundle] pathForResource:@"video-1.mp4" ofType:nil];

that is wrong, funny kind of, anyways change it to this

NSString *urlStr = [[NSBundle mainBundle] pathForResource:@"video-1" ofType:@"mp4"];

and that should be the only issue. the reason its black is because it doesn't have the right movie.

AVMutableVideoComposition doesn't play back

the answer to my question is quite simple: just update to iOS 9.3
Apple obviously has a broken framework at the moment.
There are still cases, where it doesn't work perfectly, but it's fine.
I guess it's going to be fixed in 9.4

Bye!
Andreas

Exporting a mirrored video with AVMutableComposition causes resizing issues

There is an active bug that prevents you from exporting mirrored videos correctly. You need a few workarounds:

1. Turn off the mirroring on the movieOutputFile

2. Manually flip the video horizontally when needed:

   if needsMirroring == true {
   
       var transform:CGAffineTransform = CGAffineTransform(scaleX: -1.0, y: 1.0)
       transform = transform.translatedBy(x: -naturalSize.width, y: 0.0)
       transform = transform.rotated(by: CGFloat(Double.pi/2))
       transform = transform.translatedBy(x: 0.0, y: -naturalSize.width)
       videoTransform = transform
   }
   

It took me days to figure this out, hope it helps.

Update AVMutableVideoComposition on AVPlayerItem faster than video framerate

This is a decent solution I managed to find.

I noticed that putting a sleep in the frame processing block actually seemed to improve the perceived performance.

The AVMutableVideoComposition must build up a buffer of frames and the delay I'm seeing is that buffer running out before the frames with new filter values show up. Sleeping in the frame processing block prevented the buffer from filling up making the changes show up immediately.

I looked through the documentation of AVMutableVideoComposition for the millionth time and found this little gem in the docs for sourceTrackIDForFrameTiming.

If an empty edit is encountered in the source asset’s track, the compositor composes frames as needed up to the frequency specified in frameDuration property. Otherwise the frame timing for the video composition is derived from the source asset's track with the corresponding ID.

I had previously tried setting the frameDuration on the composition but couldn't get it to go faster than the video's framerate. If I set the sourceTrackIDForFrameTiming to kCMPersistentTrackID_Invalid it actually lets me speed up the framerate.

By setting the framerate to be extremely high (1000 fps), the phone can never fill up the buffer, making the changes appear immediate.

composition.sourceTrackIDForFrameTiming = kCMPersistentTrackID_Invalid

let frameRateTooHighForPhone = CMTime(value: 1, timescale: 1000)
composition.frameDuration = frameRateTooHighForPhone

It's a little bit hackier than is ideal, but it's not a bad solution.

Export a AVMutableVideoComposition using AVAssetWriter instead of AVAssetExportSession

Set up an AVAssetReader to "read" the video frames from the AVMutableVideoComposition, and then hand them off to the AVAssetWriterInput. You would set up the asset reader with an AVAssetReaderVideoCompositionOutput, setting the videoComposition, and possibly the customVideoCompositor if needed. The custom video compositor is where you can involve your own CIFilters and anything else you want.

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