我得到了一个解码后的AVFrame,其格式显示为160/Videotoolbox_vld
。在查阅了一些文章(这里)并查看了FFmpeg源代码(这里和这里)之后,CVBuffer
句柄应该在AVFrame.data[3]
处。但是我得到的CVBuffer
似乎无效,任何CVPixelBufferGetXXX()
函数都返回0或nil。
av_hwframe_transfer_data()
,则可以将示例从HW下载到SW缓冲区。它的AVFrame.format
将是nv12
。通过sws_scale
转换为bgra
后,示例可以在视图上显示正确的内容。我认为VideoToolbox解码帧没问题。我将
AVFrame.data[3]
转换为CVBuffer
的方式可能有误。我刚学习如何在Swift中访问C指针,但我不确定如何正确读取指针中的资源句柄(CVBuffer)。以下是我尝试从AVFrame中提取CVBuffer的方式。
var pFrameOpt: UnsafeMutablePointer<AVFrame>? = av_frame_alloc()
avcodec_receive_frame(..., pFrameOpt)
let data3: UnsafeMutablePointer<UInt8>? = pFrameOpt?.pointee.data.3
data3?.withMemoryRebound(to: CVBuffer.self, capacity: 1) { pCvBuf in
let fW = pFrameOpt!.pointee.width // print 3840
let fH = pFrameOpt!.pointee.height // print 2160
let fFmt = pFrameOpt!.pointee.format // print 160
let cvBuf: CVBuffer = pCvBuf.pointee
let a1 = CVPixelBufferGetDataSize(cvBuf) // print 0
let a2 = CVPixelBufferGetPixelFormatType(cvBuf) // print 0
let a3 = CVPixelBufferGetWidth(cvBuf) // print 0
let a4 = CVPixelBufferGetHeight(cvBuf) // print 0
let a5 = CVPixelBufferGetBytesPerRow(cvBuf) // print 0
let a6 = CVPixelBufferGetBytesPerRowOfPlane(cvBuf, 0) // print 0
let a7 = CVPixelBufferGetWidthOfPlane(cvBuf, 0) // print 0
let a8 = CVPixelBufferGetHeightOfPlane(cvBuf, 0) // print 0
let a9 = CVPixelBufferGetPlaneCount(cvBuf) // print 0
let a10 = CVPixelBufferIsPlanar(cvBuf) // print false
let a11 = CVPixelBufferGetIOSurface(cvBuf) // print nil
let a12 = CVPixelBufferGetBaseAddress(cvBuf) // print nil
let a13 = CVPixelBufferGetBaseAddressOfPlane(cvBuf, 0) // print nil
let b1 = CVImageBufferGetCleanRect(cvBuf) // print 0, 0, 0, 0
let b2 = CVImageBufferGetColorSpace(cvBuf) // print nil
let b3 = CVImageBufferGetDisplaySize(cvBuf) // print 0, 0, 0, 0
let b4 = CVImageBufferGetEncodedSize(cvBuf) // print 0, 0, 0, 0
let b5 = CVImageBufferIsFlipped(cvBuf) // print false
// bad exec
var cvTextureOut: CVMetalTexture?
CVMetalTextureCacheCreateTextureFromImage(kCFAllocatorDefault, ..., cvBuf, nil, .bgra8Unorm, 3840, 2160, 0, ...)
}