AVAssetWriter failing output settings with 720p @ 60fps

Question

I have this camera app I am developing. At some point I am trying to write to video, so I am creating an assetWriter and I have these lines:

  CGFloat videoFrameWidth = size.width;
  CGFloat videoFrameHeight  = size.height;

  NSUInteger numPixels = videoFrameWidth * videoFrameHeight;
  NSUInteger bitsPerSecond;

  NSUInteger bitsPerPixel = 11.4; // This bitrate matches the quality produced by AVCaptureSessionPresetHigh... this was copied from a code from Apple

  bitsPerSecond = numPixels * bitsPerPixel;

  NSDictionary *videoCompressionSettings = @{AVVideoCodecKey                  : AVVideoCodecH264,
                                             AVVideoWidthKey                  : @(videoFrameWidth),
                                             AVVideoHeightKey                 : @(videoFrameHeight),
                                             AVVideoCompressionPropertiesKey  : @{ AVVideoAverageBitRateKey      : @(bitsPerSecond),
                                                                                   AVVideoMaxKeyFrameIntervalKey : @(fps)}
                                             };

  if ([_assetWriter canApplyOutputSettings:videoCompressionSettings forMediaType:AVMediaTypeVideo])

if I am recording at 1080p @30 fps this method works perfectly but if I switch to 720p @ 60 fps this last line fails.

Answer 1

What happens if you remove the AVVideoMaxKeyFrameIntervalKey key? I think you're saying 1 keyframe every 60 frames with that.