使用AVAssetWriter导出ScreenCaptureKit采集的CVPixelBuffer画质不佳

我在macOS上使用ScreenCaptureKit采集屏幕，功能运行正常。但通过AVAssetWriter将采集到的CVPixelBuffer导出为MP4文件时，视频画质很差。将采集帧的CVPixelBuffer转换为NSImage并保存为PNG时画质无损失，说明采集的帧未经过压缩。我尝试过多种AVAssetWriter设置组合，导出视频的画质仍不理想，以下是我的配置代码：

// Create a new AVAssetWriter to write the captured recording
// to a new file.
videoFileWriter = try? AVAssetWriter(url: prepareVideoOutputURL(), fileType: AVFileType.mp4)

let outputSettings: [String : Any] = [
    AVVideoCodecKey : AVVideoCodecType.hevc ,
    AVVideoHeightKey: frame.size.height - CGFloat(Self.topCropHeightWithoutScalingInPixels)/scaleFactor,
    AVVideoWidthKey: frame.size.width,
    AVVideoCompressionPropertiesKey: [
        AVVideoAllowFrameReorderingKey: false,
        AVVideoExpectedSourceFrameRateKey: numberOfFramePerSecond,
        AVVideoMaxKeyFrameIntervalKey: numberOfFramePerSecond,
        AVVideoMaxKeyFrameIntervalDurationKey: 1
    ],
    // HD Color space https://developer.apple.com/library/archive/technotes/tn2227/_index.html
    // https://developer.apple.com/documentation/avfoundation/media_reading_and_writing/tagging_media_with_video_color_information
    AVVideoColorPropertiesKey: [
        AVVideoColorPrimariesKey: AVVideoColorPrimaries_ITU_R_709_2,
        AVVideoTransferFunctionKey: AVVideoTransferFunction_ITU_R_709_2,
        AVVideoYCbCrMatrixKey: AVVideoYCbCrMatrix_ITU_R_709_2
    ]
]

videoWriterInput = AVAssetWriterInput(
    mediaType: AVMediaType.video,
    outputSettings: outputSettings,
    sourceFormatHint: nil
)
if videoFileWriter.canAdd(videoWriterInput) {
    videoFileWriter.add(videoWriterInput)
}

videoWriterInputAdapter = AVAssetWriterInputPixelBufferAdaptor(
    assetWriterInput: videoWriterInput,
    sourcePixelBufferAttributes: nil
)

• 画质良好的PNG帧截图：
  

• 画质较差的视频帧截图：
  

内容的提问来源于stack exchange，提问作者Peacemoon