VideoToolbox encoder output full-range h264 stream

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Created Nov ’20

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When we send CVPixelBufferRef of kCVPixelFormatType_32BGRA to VideoToolbox H264 encoder, VideoToolbox used to convert the image to YUV Video Range and then encode it.

But starting from ios14.0 , VideoToolbox will convert the image to YUV Full Range.

We can verify it by checking the VUI of the produced H264 stream.

Can some one explain the reason why the behavior of system API is changed, and how can I alter this behavior ?

Thanks a lot
Shumin

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shumin888 OP

Dec ’20

update:
It starts from ios14.2, not 14.0.
According to our test, beginning from ios14.2, videoToolbox will convert BGRA to NV12 using bt.709 Full Range.
Before that, the system use bt.601 Video Range.

Is there an API to let me change this behavior ?

I have tried to set kVTCompressionPropertyKey_YCbCrMatrix, but it doesn't work.

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