AVAssetWriter输出设置失败，720p @ 60fps

Question

我正在开发这款相机应用程序。在某些时候我试图写入视频，所以我正在创建一个assetWriter，我有这些行：

  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])

如果我以1080p @ 30 fps进行录制，这种方法可以正常工作，但如果我切换到720p @ 60 fps，则最后一行会失败。

Answer 1

如果删除AVVideoMaxKeyFrameIntervalKey密钥会怎样？我认为你每隔60帧就会说一个关键帧。