Update about packed and planar YUV formats

AlexxIT · Jan 10, 2025 · 8390713 · 8390713
1 parent 7dc9beb
commit 8390713
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Showing 4 changed files with 19 additions and 5 deletions.
diff --git a/pkg/v4l2/device/device.go b/pkg/v4l2/device/device.go
@@ -196,7 +196,7 @@ func (d *Device) StreamOff() (err error) {
 	return ioctl(d.fd, VIDIOC_REQBUFS, unsafe.Pointer(&rb))
 }
 
-func (d *Device) Capture(cositedYUV bool) ([]byte, error) {
+func (d *Device) Capture(planarYUV bool) ([]byte, error) {
 	dec := v4l2_buffer{
 		typ:    V4L2_BUF_TYPE_VIDEO_CAPTURE,
 		memory: V4L2_MEMORY_MMAP,
@@ -206,7 +206,7 @@ func (d *Device) Capture(cositedYUV bool) ([]byte, error) {
 	}
 
 	buf := make([]byte, dec.bytesused)
-	if cositedYUV {
+	if planarYUV {
 		YUYV2YUV(buf, d.bufs[dec.index][:dec.bytesused])
 	} else {
 		copy(buf, d.bufs[dec.index][:dec.bytesused])

diff --git a/pkg/v4l2/device/formats.go b/pkg/v4l2/device/formats.go
@@ -16,7 +16,7 @@ var Formats = []Format{
 	{V4L2_PIX_FMT_MJPEG, "Motion-JPEG", "mjpeg"},
 }
 
-// YUYV2YUV convert [Y0 Cb Y1 Cr] to cosited [Y0Y1... Cb... Cr...]
+// YUYV2YUV convert packed YUV to planar YUV
 func YUYV2YUV(dst, src []byte) {
 	n := len(src)
 	i0 := 0

diff --git a/pkg/v4l2/producer.go b/pkg/v4l2/producer.go
@@ -93,10 +93,10 @@ func (c *Producer) Start() error {
 		return err
 	}
 
-	cositedYUV := c.Medias[0].Codecs[0].Name == core.CodecRAW
+	planarYUV := c.Medias[0].Codecs[0].Name == core.CodecRAW
 
 	for {
-		buf, err := c.dev.Capture(cositedYUV)
+		buf, err := c.dev.Capture(planarYUV)
 		if err != nil {
 			return err
 		}

diff --git a/pkg/y4m/README.md b/pkg/y4m/README.md
@@ -1,5 +1,19 @@
+## Planar YUV formats
+
+Packed YUV - yuyv422 - YUYV 4:2:2
+Semi-Planar - nv12 - Y/CbCr 4:2:0
+Planar YUV - yuv420p - Planar YUV 4:2:0 - aka. [cosited](https://manned.org/yuv4mpeg.5)
+
+```
+[video4linux2,v4l2 @ 0x55fddc42a940] Raw       :     yuyv422 :           YUYV 4:2:2 : 1920x1080
+[video4linux2,v4l2 @ 0x55fddc42a940] Raw       :        nv12 :         Y/CbCr 4:2:0 : 1920x1080
+[video4linux2,v4l2 @ 0x55fddc42a940] Raw       :     yuv420p :     Planar YUV 4:2:0 : 1920x1080
+```
+
 ## Useful links
 
 - https://learn.microsoft.com/en-us/windows/win32/medfound/recommended-8-bit-yuv-formats-for-video-rendering
 - https://developer.mozilla.org/en-US/docs/Web/Media/Formats/Video_concepts
 - https://fourcc.org/yuv.php#YV12
+- https://docs.kernel.org/userspace-api/media/v4l/pixfmt-yuv-planar.html
+- https://gist.github.com/Jim-Bar/3cbba684a71d1a9d468a6711a6eddbeb