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标题: ios - CVPixelBufferGetBaseAddress 返回空 VTDecompressionSessionDecodeFrame 回调 [打印本页]

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作者: 菜鸟教程小白    时间: 2022-12-12 11:40
标题: ios - CVPixelBufferGetBaseAddress 返回空 VTDecompressionSessionDecodeFrame 回调

我正在使用 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 为 0，所以我的假设是这里没有任何问题。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:这里也是 CVImageBufferRef 对象的转储。看起来可疑的一件事是我希望有 3 个平面(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。我正在实现它以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需要它。

{type = immutable dict, count = 5, entries => 0 : {contents = "ixelFormatDescription"} = {type = immutable dict, count = 10, entries => 0 : {contents = "lanes"} = {type = mutable-small, count = 2, values = ( 0 : {type = mutable dict, count = 3, entries => 0 : {contents = "FillExtendedPixelsCallback"} = {length = 24, capacity = 24, bytes = 0x000000000000000030139783010000000000000000000000} 1 : {contents = "BitsPerBlock"} = {value = +8, type = kCFNumberSInt32Type} 2 : {contents = "BlackBlock"} = {length = 1, capacity = 1, bytes = 0x10} }

1 : {type = mutable dict, count = 5, entries => 2 : {contents = "HorizontalSubsampling"} = {value = +2, type = kCFNumberSInt32Type} 3 : {contents = "BlackBlock"} = {length = 2, capacity = 2, bytes = 0x8080} 4 : {contents = "BitsPerBlock"} = {value = +16, type = kCFNumberSInt32Type} 5 : {contents = "VerticalSubsampling"} = {value = +2, type = kCFNumberSInt32Type} 6 : {contents = "FillExtendedPixelsCallback"} = {length = 24, capacity = 24, bytes = 0x0000000000000000ac119783010000000000000000000000} }

)} 2 : {contents = "IOSurfaceOpenGLESFBOCompatibility"} = {value = true} 3 : {contents = "ContainsYCbCr"} = {value = true} 4 : {contents = "IOSurfaceOpenGLESTextureCompatibility"} = {value = true} 5 : {contents = "ComponentRange"} = {contents = "VideoRange"} 6 : {contents = "ixelFormat"} = {value = +875704438, type = kCFNumberSInt32Type} 7 : {contents = "IOSurfaceCoreAnimationCompatibility"} = {value = true} 9 : {contents = "ContainsAlpha"} = {value = false} 10 : {contents = "ContainsRGB"} = {value = false} 11 : {contents = "OpenGLESCompatibility"} = {value = true} }

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

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Best Answer-推荐答案

所以您的格式是 kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange = '420v' 并且两个平面对于 4:2:0 YUV 数据有意义，因为第一个平面是全尺寸 Y 单 channel 位图，第二个平面是半宽半高UV双 channel 位图。

你是对的，对于平面数据，你应该调用 CVPixelBufferGetBaseAddressOfPlane，虽然你应该能够使用 CVPixelBufferGetBaseAddress，将其结果解释为 CVPlanarPixelBufferInfo_YCbCrBiPlanar，所以问题可能是您没有在 CVPixelBufferGetBaseAddress* 之前调用 CVPixelBufferLockBaseAddress 也没有在之后调用 CVPixelBufferUnlockBaseAddress。

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

关于ios - CVPixelBufferGetBaseAddress 返回空 VTDecompressionSessionDecodeFrame 回调，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/37887639/

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