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l1npengtul / nokhwa

Cross Platform Rust Library for Powerful Webcam/Camera Capture
Apache License 2.0
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yuv422 confusions? #146

Open yamt opened 9 months ago

yamt commented 9 months ago

this is about 0.10 branch as senpai is not buildable for me.

  1. nokhwa-bindings-macos seems to map both of kCMVideoCodecType_422YpCbCr8 and kCMPixelFormat_422YpCbCr8_yuvs to FrameFormat::YUYV. according to apple docs, kCMVideoCodecType_422YpCbCr8 is "ordered Cb Y'0 Cr Y'1" and kCMPixelFormat_422YpCbCr8_yuvs is "ordered Y'0 Cb Y'1 Cr." on the other hand, buf_yuyv422_to_rgb seems assuming the latter ordering.

  2. on my environment (MacBook Pro (15-inch, 2018)) the camera on the top of the display seems to report kCMPixelFormat_422YpCbCr8_yuvs. (confirmed by adding debug code in raw_fcc_to_frameformat) however, for some reasons, using the threaded-capture example, the buffers given to the callback actually seem to contain bytes in "Cb Y'0 Cr Y'1" order. (thus decoded wrong.)

cf. https://developer.apple.com/documentation/coremedia/1564239-video_codec_constants/kcmvideocodectype_422ypcbcr8 https://developer.apple.com/documentation/coremedia/1564244-video_pixel_format_constants/kcmpixelformat_422ypcbcr8_yuvs

l1npengtul commented 9 months ago

Thank you for your comment, I did not see that when I originally wrote that code. I will fix this in the upcoming release.

yamt commented 9 months ago

on my environment (MacBook Pro (15-inch, 2018)) the camera on the top of the display seems to report kCMPixelFormat_422YpCbCr8_yuvs. (confirmed by adding debug code in raw_fcc_to_frameformat) however, for some reasons, using the threaded-capture example, the buffers given to the callback actually seem to contain bytes in "Cb Y'0 Cr Y'1" order. (thus decoded wrong.)

https://github.com/l1npengtul/nokhwa/pull/151 fixes this part.