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使用 VTDecompressionSessionDecodeFrame 时，我在通过 rtsp 流式传输原始 H.265 时遇到了一些问题。我做的 3 个主要步骤如下：

OSStatus status = CMVideoFormatDescriptionCreateFromHEVCParameterSets(kCFAllocatorDefault, 3, parameterSetPointers, parameterSetSizes, (int)kNALUHeaderSize, NULL, &formatDescription);

OSStatus status = VTDecompressionSessionCreate(NULL, formatDescription, NULL, NULL, &decompressionCallBack, &_decompressionSession);

VTDecompressionSessionDecodeFrame(self.decompressionSession, sampleBuffer, flags, (void *)CFBridgingRetain(currentTime), NULL);

格式描述如下所示：

<CMVideoFormatDescription 0x1c0044d10 [0x1b2bb1310]> {
mediaType:'vide' 
mediaSubType:'hvc1' 
mediaSpecific: {
    codecType: 'hvc1'       dimensions: 640 x 360 
} 
extensions: {<CFBasicHash 0x1c00742c0 [0x1b2bb1310]>{type = immutable dict, count = 10,
entries =>
0 : <CFString 0x1ab8dd470 [0x1b2bb1310]>{contents = "SampleDescriptionExtensionAtoms"} = <CFBasicHash 0x1c0074140 [0x1b2bb1310]>{type = immutable dict, count = 1,
entries =>
0 : hvcC = <CFData 0x1c01678c0 [0x1b2bb1310]>{length = 115, capacity = 115, bytes = 0x01016000000000008000000042f000fc ... 4401d172b0942b12}
}

1 : <CFString 0x1ab8b8ff8 [0x1b2bb1310]>{contents = "CVImageBufferYCbCrMatrix"} = <CFString 0x1ab8b9018 [0x1b2bb1310]>{contents = "ITU_R_709_2"}
2 : <CFString 0x1ab8b92b8 [0x1b2bb1310]>{contents = "CVImageBufferChromaLocationTopField"} = <CFString 0x1ab8b92f8 [0x1b2bb1310]>{contents = "Left"}
3 : <CFString 0x1ab8b8f38 [0x1b2bb1310]>{contents = "CVPixelAspectRatio"} = <CFBasicHash 0x1c0074280 [0x1b2bb1310]>{type = immutable dict, count = 2,
entries =>
1 : <CFString 0x1ab8b8f58 [0x1b2bb1310]>{contents = "HorizontalSpacing"} = <CFNumber 0xb000000000000012 [0x1b2bb1310]>{value = +1, type = kCFNumberSInt32Type}
2 : <CFString 0x1ab8b8f78 [0x1b2bb1310]>{contents = "VerticalSpacing"} = <CFNumber 0xb000000000000012 [0x1b2bb1310]>{value = +1, type = kCFNumberSInt32Type}
}

5 : <CFString 0x1ab8b90d8 [0x1b2bb1310]>{contents = "CVImageBufferColorPrimaries"} = <CFString 0x1ab8b9018 [0x1b2bb1310]>{contents = "ITU_R_709_2"}
6 : <CFString 0x1ab8dd670 [0x1b2bb1310]>{contents = "FullRangeVideo"} = <CFBoolean 0x1b2bb1868 [0x1b2bb1310]>{value = true}
8 : <CFString 0x1ab8b9158 [0x1b2bb1310]>{contents = "CVImageBufferTransferFunction"} = <CFString 0x1ab8b9018 [0x1b2bb1310]>{contents = "ITU_R_709_2"}
10 : <CFString 0x1ab8b92d8 [0x1b2bb1310]>{contents = "CVImageBufferChromaLocationBottomField"} = <CFString 0x1ab8b92f8 [0x1b2bb1310]>{contents = "Left"}
11 : <CFString 0x1ab8ddc10 [0x1b2bb1310]>{contents = "BitsPerComponent"} = <CFNumber 0xb000000000000080 [0x1b2bb1310]>{value = +8, type = kCFNumberSInt8Type}
12 : <CFString 0x1ab8b8e78 [0x1b2bb1310]>{contents = "CVFieldCount"} = <CFNumber 0xb000000000000012 [0x1b2bb1310]>{value = +1, type = kCFNumberSInt32Type}
}
}
}

解码帧时，我在解压缩回调中得到 OSStatus -12909。因此，我认为在创建格式描述时正确处理了 VPS、PPS 和 SPS。解压会话也已成功创建。我还可以成功解码和渲染 HEVC 流，例如这个：如果将 CMVideoFormatDescriptionCreateFromHEVCParameterSets 更改为 CMVideoFormatDescriptionCreateFromH264ParameterSets，则该解决方案在流式传输原始 H.264 时也有效。

有什么想法可能是错的吗？是否支持格式描述？遗憾的是，苹果方面没有太多关于 HEVC 解码的文档。如果使用 ffmpeg，我可以流式传输我的 H.265 流，所以我猜流应该是正确格式的。

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