ios - 裁剪录制的视频帧

Question

我正在尝试裁剪视频帧。我使用 AVFoundation 框架录制了视频。我需要将拍摄的图像和录制的视频裁剪成方形。我已经为有效的 UIImage 完成了它，现在我正在尝试裁剪视频。

- (UIImage *)squareImageWithImage:(UIImage *)image scaledToSize:(CGSize)newSize {
  // Cropping UIImage is working fine.
  CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], CGRectMake(0,0, image.size.width, image.size.width));
  UIImage *result = [UIImage imageWithCGImage:imageRef scale:image.scale orientation:image.imageOrientation];
  CGImageRelease(imageRef);
  return result;
}

我尝试裁剪视频，但结果是在没有裁剪的情况下改变了整个视频帧，而且看起来被拉伸(stretch)了。

_writer = [AVAssetWriter assetWriterWithURL:url fileType:AVFileTypeQuickTimeMovie error:nil];
NSDictionary* settings = [NSDictionary dictionaryWithObjectsAndKeys:
                          AVVideoCodecH264, AVVideoCodecKey,
                          [NSNumber numberWithInt: 320], AVVideoWidthKey,
                          [NSNumber numberWithInt: 320], AVVideoHeightKey,
                          nil];
_videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:settings];
[_writer addInput:_videoInput];

谁能帮我解决这个视频裁剪问题？提前致谢。

Answer 1

下面是我用于裁剪视频的代码。我们需要设置 AVVideoCompressionPropertiesKey，其中包含用于视频设置的 AVVideoCleanApertureKey 键。

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NSDictionary *videoCleanApertureSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                            [NSNumber numberWithInt:cx], AVVideoCleanApertureWidthKey,
                                            [NSNumber numberWithInt:cx], AVVideoCleanApertureHeightKey,
                                            [NSNumber numberWithInt:10], AVVideoCleanApertureHorizontalOffsetKey,
                                            [NSNumber numberWithInt:10], AVVideoCleanApertureVerticalOffsetKey,
                                            nil];
NSDictionary *videoAspectRatioSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                                          [NSNumber numberWithInt:3], AVVideoPixelAspectRatioHorizontalSpacingKey,
                                          [NSNumber numberWithInt:3],AVVideoPixelAspectRatioVerticalSpacingKey,
                                          nil];
NSDictionary *codecSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               [NSNumber numberWithInt:960000], AVVideoAverageBitRateKey,
                               [NSNumber numberWithInt:1],AVVideoMaxKeyFrameIntervalKey,
                               videoCleanApertureSettings, AVVideoCleanApertureKey,
                               //videoAspectRatioSettings, AVVideoPixelAspectRatioKey,
                               //AVVideoProfileLevelH264Main30, AVVideoProfileLevelKey,
                               nil];
NSString *targetDevice = [[UIDevice currentDevice] model];
NSDictionary *videoSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                               AVVideoScalingModeResizeAspectFill,AVVideoScalingModeKey,
                               AVVideoCodecH264, AVVideoCodecKey,
                               codecSettings,AVVideoCompressionPropertiesKey,
                               [NSNumber numberWithInt:cx], AVVideoWidthKey,
                               [NSNumber numberWithInt:cx], AVVideoHeightKey,
                               nil];
_videoInput = [AVAssetWriterInput assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:videoSettings];