mediadevices/pkg/frame/yuv.go

package frame

import (
	"fmt"
	"image"
)

func decodeI420() decoderFunc {
	return func(frame []byte, width, height int) (image.Image, func(), error) {
		yi := width * height
		cbi := yi + width*height/4
		cri := cbi + width*height/4

		if cri > len(frame) {
			return nil, func() {}, fmt.Errorf("frame length (%d) less than expected (%d)", len(frame), cri)
		}

		return &image.YCbCr{
			Y:              frame[:yi],
			YStride:        width,
			Cb:             frame[yi:cbi],
			Cr:             frame[cbi:cri],
			CStride:        width / 2,
			SubsampleRatio: image.YCbCrSubsampleRatio420,
			Rect:           image.Rect(0, 0, width, height),
		}, func() {}, nil
	}
}

func decodeNV21() decoderFunc {
	return func(frame []byte, width, height int) (image.Image, func(), error) {
		yi := width * height
		ci := yi + width*height/2

		if ci > len(frame) {
			return nil, func() {}, fmt.Errorf("frame length (%d) less than expected (%d)", len(frame), ci)
		}

		var cb, cr []byte
		for i := yi; i < ci; i += 2 {
			cb = append(cb, frame[i])
			cr = append(cr, frame[i+1])
		}

		return &image.YCbCr{
			Y:              frame[:yi],
			YStride:        width,
			Cb:             cb,
			Cr:             cr,
			CStride:        width / 2,
			SubsampleRatio: image.YCbCrSubsampleRatio420,
			Rect:           image.Rect(0, 0, width, height),
		}, func() {}, nil
	}
}