Question

我使用VTDecompressionSession通过网络解码H.264流。我需要从给定的图像缓冲区复制YUV缓冲区。我已经验证了给定的imageBuffer的typeID等于CVPixelBufferGetTypeID()。

但每当我尝试检索缓冲区或任何平面的基地址时，它们总是返回NULL。 iOS传递的OSStatus是0，所以我的假设是这里没有错。也许我不知道如何提取数据。有人可以帮忙吗？

void decompressionCallback(void * CM_NULLABLE decompressionOutputRefCon,
                           void * CM_NULLABLE sourceFrameRefCon,
                           OSStatus status,
                           VTDecodeInfoFlags infoFlags,
                           CM_NULLABLE CVImageBufferRef imageBuffer,
                           CMTime presentationTimeStamp, 
                           CMTime presentationDuration )
{
    CFShow(imageBuffer);
    size_t dataSize = CVPixelBufferGetDataSize(imageBuffer);
    void * decodedBuffer = CVPixelBufferGetBaseAddress(imageBuffer);
    memcpy(pYUVBuffer, decodedBuffer, dataSize);
}

编辑：此处还有CVImageBufferRef对象的转储。有点可疑的是，我希望有3架飞机（Y，U和V）。但是只有两架飞机。我的期望是使用CVPixelBufferGetBaseAddressOfPlane来提取每个数据平面。我实现这一点是为了消除对单独软件编解码器的依赖，因此我需要以这种方式提取每个平面，因为我的渲染管道的其余部分都需要它。

  {type = immutable   dict，count = 5，entries =＆gt; 0：{contents =＆＃34; PixelFormatDescription＆＃34;} = {type = immutable dict，count = 10，entries   =＆GT; 0：{contents =＆＃34; Planes＆＃34;} = {type = mutable-small，count = 2，   values =（0：{type = mutable   dict，count = 3，entries =＆gt; 0：{contents =＆＃34; FillExtendedPixelsCallback＆＃34;} = {length = 24，capacity = 24，bytes =   0x000000000000000030139783010000000000000000000000} 1：{contents =＆＃34; BitsPerBlock＆＃34;} = {value = + 8，type =   kCFNumberSInt32Type} 2：{contents =＆＃34; BlackBlock＆＃34;} = {length = 1，capacity = 1，bytes = 0x10}}

1：{type = mutable dict，   count = 5，entries =＆gt; 2：{contents =＆＃34; HorizontalSubsampling＆＃34;} = {value = + 2，type =   kCFNumberSInt32Type} 3：{contents =＆＃34; BlackBlock＆＃34;} = {length = 2，capacity = 2，bytes = 0x8080} 4：   {contents =＆＃34; BitsPerBlock＆＃34;} =   {value = + 16，type =   kCFNumberSInt32Type} 5：{contents =＆＃34; VerticalSubsampling＆＃34;} = {value = + 2，type =   kCFNumberSInt32Type} 6：{contents =＆＃34; FillExtendedPixelsCallback＆＃34;} = {length = 24，capacity = 24，bytes =   0x0000000000000000ac1197830100000000000000000000000000}}

）} 2：{contents =   ＆＃34; IOSurfaceOpenGLESFBOCompatibility＆＃34;} = {value = true} 3：{contents =＆＃34; ContainsYCbCr＆＃34;} = {value = true} 4：{contents =＆＃34; IOSurfaceOpenGLESTextureCompatibility＆＃34;} =   {value = true} 5：{contents =＆＃34; ComponentRange＆＃34;} = {contents =＆＃34; VideoRange＆＃34;} 6：{contents =＆＃34; PixelFormat＆＃34;} = {value = +875704438，类型=   kCFNumberSInt32Type} 7：{contents =＆＃34; IOSurfaceCoreAnimationCompatibility＆＃34;} =   {value = true} 9：{contents =＆＃34; ContainsAlpha＆＃34;} = {value = false} 10：{contents =＆＃34; ContainsRGB＆＃34;} = {value = false} 11：{contents = ＆＃34; OpenGLESCompatibility＆＃34;} = {value = true}}

2：{contents =   ＆＃34; ExtendedPixelsRight＆＃34;} = {value = + 8，type = kCFNumberSInt32Type} 3：{contents =＆＃34; ExtendedPixelsTop＆＃34;} = {value = + 0，type =   kCFNumberSInt32Type} 4：{contents =＆＃34; ExtendedPixelsLeft＆＃34;} = {value = + 0，type =   kCFNumberSInt32Type} 5：{contents =＆＃34; ExtendedPixelsBottom＆＃34;} = {value = + 0，type =   kCFNumberSInt32Type}} propagatedAttachments = {type = mutable dict，count = 7，entries =＆gt; 0：   {contents =   ＆＃34; CVImageBufferChromaLocationTopField＆＃34;} =左1：{contents =＆＃34; CVImageBufferYCbCrMatrix＆＃34;} =   {contents =＆＃34; ITU_R_601_4＆＃34;} 2：   {contents =＆＃34; ColorInfoGuessedBy＆＃34;}   = {contents =＆＃34; VideoToolbox＆＃34;} 5：{contents =   ＆＃34; CVImageBufferColorPrimaries＆＃34;} = SMPTE_C 8：{contents =＆＃34; CVImageBufferTransferFunction＆＃34;} = {contents =＆＃34; ITU_R_709_2＆＃34;} 10：{contents =   ＆＃34; CVImageBufferChromaLocationBottomField＆＃34;} =左12：{contents =＆＃34; CVFieldCount＆＃34;} = {value = +1，type =   kCFNumberSInt32Type}} nonPropagatedAttachments = {type = mutable dict，count = 0，entries =＆gt;   }

Answer 1

所以你的格式为kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange = '420v'，两个平面对4：2：0 YUV数据有意义，因为第一个平面是全尺寸Y单通道位图，第二个是半宽半高UV双通道位图。

你是对的，对于你应该调用CVPixelBufferGetBaseAddressOfPlane的平面数据，虽然你应该能够使用CVPixelBufferGetBaseAddress，将其结果解释为CVPlanarPixelBufferInfo_YCbCrBiPlanar，所以问题可能是你之后CVPixelBufferLockBaseAddress之前没有呼叫CVPixelBufferGetBaseAddress*，之后也没有呼叫CVPixelBufferUnlockBaseAddress。

从这里你可以通过编写一些有趣的YUV-> RGB着色器代码，使用Metal或OpenGL有效地显示2个YUV平面。

CVPixelBufferGetBaseAddress返回null VTDecompressionSessionDecodeFrame回调

1 个答案: