如何将CMSampleBuffer / UIImage转换为ffmpeg的AVPicture？

CVImageBufferRef pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer);
CVPixelBufferLockBaseAddress(pixelBuffer, 0);

// access the data
int width = CVPixelBufferGetWidth(pixelBuffer);
int height = CVPixelBufferGetHeight(pixelBuffer);
unsigned char *rawPixelBase = (unsigned char *)CVPixelBufferGetBaseAddress(pixelBuffer);

// Do something with the raw pixels here
// ...

// Fill in the AVFrame
CVPixelBufferUnlockBaseAddress(pixelBuffer, 0);

AVFrame *pFrame;
pFrame = avcodec_alloc_frame();

avpicture_fill((AVPicture*)pFrame, rawPixelBase, PIX_FMT_RGB32, width, height);

pFrame

kCVPixelFormatType_32BGRA