On Fri Aug 7 03:46:47 2026 -0400, Ben Hoff wrote:
> At 1920x1080, the driver advertises V4L2_COLORSPACE_REC709 with
> V4L2_YCBCR_ENC_DEFAULT. The default maps to a Rec.709 matrix, but
> controlled A/B captures using the in-tree and baseline drivers show that
> both produce YUYV samples using a BT.601 matrix and full-range
> quantization. The captures differ by at most one code value, whereas a
> 601-to-709 conversion would move primary luma values by roughly 11 to 33
> codes.
>
> Set the Y'CbCr encoding explicitly to V4L2_YCBCR_ENC_601 at every
> resolution. Keep the resolution-based colorspace so HD retains presumed
> Rec.709 primaries and transfer characteristics while SD continues to use
> SMPTE 170M. Refresh the colorspace on detected geometry changes so an
> SD/HD transition does not leave stale metadata.
>
> The decoder mode register is undocumented. Stop claiming that value 0x13
> selects BT.709; both drivers use that value while producing the measured
> output.
>
> Fixes: ba07fd2f5742 ("media: pci: add AVMatrix HWS capture driver")
> Cc: [email protected]
> Assisted-by: Codex:gpt-5.6
> Signed-off-by: Ben Hoff <[email protected]>
> Signed-off-by: Hans Verkuil <[email protected]>
Patch committed.
Thanks,
Hans Verkuil
drivers/media/pci/hws/hws.h | 4 ++--
drivers/media/pci/hws/hws_reg.h | 3 ++-
drivers/media/pci/hws/hws_v4l2_ioctl.c | 5 +++--
drivers/media/pci/hws/hws_video.c | 4 +++-
4 files changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/drivers/media/pci/hws/hws.h b/drivers/media/pci/hws/hws.h
index 8fbe1fe27844..d87d52674b69 100644
--- a/drivers/media/pci/hws/hws.h
+++ b/drivers/media/pci/hws/hws.h
@@ -33,8 +33,8 @@ struct hws_pix_state {
u32 sizeimage; /* full frame */
enum v4l2_field field; /* V4L2_FIELD_NONE or INTERLACED */
enum v4l2_colorspace colorspace; /* e.g., REC709 */
- enum v4l2_ycbcr_encoding ycbcr_enc; /* V4L2_YCBCR_ENC_DEFAULT */
- enum v4l2_quantization quantization; /* V4L2_QUANTIZATION_LIM_RANGE
*/
+ enum v4l2_ycbcr_encoding ycbcr_enc; /* V4L2_YCBCR_ENC_601 */
+ enum v4l2_quantization quantization; /* V4L2_QUANTIZATION_FULL_RANGE
*/
enum v4l2_xfer_func xfer_func; /* V4L2_XFER_FUNC_DEFAULT */
bool interlaced; /* cached hardware state */
u32 half_size; /* hardware half-frame size */
diff --git a/drivers/media/pci/hws/hws_reg.h b/drivers/media/pci/hws/hws_reg.h
index ac607360d628..ba1d22f4376c 100644
--- a/drivers/media/pci/hws/hws_reg.h
+++ b/drivers/media/pci/hws/hws_reg.h
@@ -70,7 +70,8 @@
#define HWS_CTL_IRQ_ENABLE_BIT BIT(0) /* Global interrupt enable bit */
/* Write 0x00 to fully reset decoder,
* set bit 31=1 to "start run",
- * low byte=0x13 selects YUYV/BT.709/etc,
+ * low byte=0x13 is the vendor baseline capture-mode value; its individual
+ * bit meanings are not documented,
* in ReadChipId() we also write 0x00 and 0x10 here for chip-ID sequencing.
*/
diff --git a/drivers/media/pci/hws/hws_v4l2_ioctl.c
b/drivers/media/pci/hws/hws_v4l2_ioctl.c
index 0303e311ee4a..ce396b7225d2 100644
--- a/drivers/media/pci/hws/hws_v4l2_ioctl.c
+++ b/drivers/media/pci/hws/hws_v4l2_ioctl.c
@@ -511,8 +511,9 @@ static inline void hws_set_colorimetry_state(struct
hws_pix_state *p)
{
bool sd = p->height <= 576;
+ /* Captured samples use full-range BT.601 Y'CbCr at every resolution. */
p->colorspace = sd ? V4L2_COLORSPACE_SMPTE170M :
V4L2_COLORSPACE_REC709;
- p->ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
+ p->ycbcr_enc = V4L2_YCBCR_ENC_601;
p->quantization = V4L2_QUANTIZATION_FULL_RANGE;
p->xfer_func = V4L2_XFER_FUNC_DEFAULT;
}
@@ -736,7 +737,7 @@ static inline void hws_set_colorimetry_fmt(struct
v4l2_pix_format *p)
bool sd = p->height <= 576;
p->colorspace = sd ? V4L2_COLORSPACE_SMPTE170M :
V4L2_COLORSPACE_REC709;
- p->ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
+ p->ycbcr_enc = V4L2_YCBCR_ENC_601;
p->quantization = V4L2_QUANTIZATION_FULL_RANGE;
p->xfer_func = V4L2_XFER_FUNC_DEFAULT;
}
diff --git a/drivers/media/pci/hws/hws_video.c
b/drivers/media/pci/hws/hws_video.c
index 18e4bc6901d3..09cfb5a909f9 100644
--- a/drivers/media/pci/hws/hws_video.c
+++ b/drivers/media/pci/hws/hws_video.c
@@ -327,7 +327,7 @@ int hws_video_init_channel(struct hws_pcie_dev *pdev, int
ch)
vid->pix.sizeimage = vid->pix.bytesperline * vid->pix.height;
vid->pix.field = V4L2_FIELD_NONE;
vid->pix.colorspace = V4L2_COLORSPACE_REC709;
- vid->pix.ycbcr_enc = V4L2_YCBCR_ENC_DEFAULT;
+ vid->pix.ycbcr_enc = V4L2_YCBCR_ENC_601;
vid->pix.quantization = V4L2_QUANTIZATION_FULL_RANGE;
vid->pix.xfer_func = V4L2_XFER_FUNC_DEFAULT;
vid->pix.interlaced = false;
@@ -895,6 +895,8 @@ static void hws_video_apply_mode_change(struct hws_pcie_dev
*pdx,
v->pix.width = w;
v->pix.height = h;
v->pix.interlaced = interlaced;
+ v->pix.colorspace = h <= 576 ? V4L2_COLORSPACE_SMPTE170M :
+ V4L2_COLORSPACE_REC709;
hws_set_current_dv_timings(v, w, h, interlaced);
v->current_fps = fps;
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