Messages in this thread | | | Subject | Re: [PATCH v6 2/7] gpu: ipu-v3: ipu-ic: Fix BT.601 coefficients | From | Steve Longerbeam <> | Date | Fri, 8 Mar 2019 17:00:17 -0800 |
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On 3/8/19 2:23 AM, Philipp Zabel wrote: > Hi Steve, > > On Thu, 2019-03-07 at 15:33 -0800, Steve Longerbeam wrote: >> The ycbcr2rgb and inverse rgb2ycbcr tables define the BT.601 Y'CbCr >> encoding coefficients. >> >> The rgb2ycbcr table specifically describes the BT.601 encoding from >> full range RGB to full range YUV. Add table comments to make this more >> clear. >> >> The ycbcr2rgb inverse table describes encoding YUV limited range to RGB >> full range. To be consistent with the rgb2ycbcr table, convert this to >> YUV full range to RGB full range, and adjust/expand on the comments. >> >> The ic_csc_rgb2rgb table is just an identity matrix, so rename to >> ic_encode_identity. >> >> Fixes: 1aa8ea0d2bd5d ("gpu: ipu-v3: Add Image Converter unit") >> >> Suggested-by: Philipp Zabel <p.zabel@pengutronix.de> >> Signed-off-by: Steve Longerbeam <slongerbeam@gmail.com> >> Cc: stable@vger.kernel.org >> --- >> drivers/gpu/ipu-v3/ipu-ic.c | 61 ++++++++++++++++++++++--------------- >> 1 file changed, 37 insertions(+), 24 deletions(-) >> >> diff --git a/drivers/gpu/ipu-v3/ipu-ic.c b/drivers/gpu/ipu-v3/ipu-ic.c >> index 18816ccf600e..b63a2826b629 100644 >> --- a/drivers/gpu/ipu-v3/ipu-ic.c >> +++ b/drivers/gpu/ipu-v3/ipu-ic.c >> @@ -175,7 +175,7 @@ static inline void ipu_ic_write(struct ipu_ic *ic, u32 value, unsigned offset) >> writel(value, ic->priv->base + offset); >> } >> >> -struct ic_csc_params { >> +struct ic_encode_coeff { > This less accurate. These are called IC (Task) Parameters in the > reference manual, the 64-bit aligned words are called CSC words. Beside > the coefficients, this structure also contains the coefficient scale, > the offsets, and the saturation mode flag.
It seemed to me the renaming was more clear, but I agree the former name conforms better to the manual nomenclature. I will revert this renaming.
> >> s16 coeff[3][3]; /* signed 9-bit integer coefficients */ >> s16 offset[3]; /* signed 11+2-bit fixed point offset */ >> u8 scale:2; /* scale coefficients * 2^(scale-1) */ >> @@ -183,13 +183,15 @@ struct ic_csc_params { >> }; >> >> /* >> - * Y = R * .299 + G * .587 + B * .114; >> - * U = R * -.169 + G * -.332 + B * .500 + 128.; >> - * V = R * .500 + G * -.419 + B * -.0813 + 128.; >> + * BT.601 encoding from RGB full range to YUV full range: >> + * >> + * Y = .2990 * R + .5870 * G + .1140 * B >> + * U = -.1687 * R - .3313 * G + .5000 * B + 128 >> + * V = .5000 * R - .4187 * G - .0813 * B + 128 >> */ >> -static const struct ic_csc_params ic_csc_rgb2ycbcr = { >> +static const struct ic_encode_coeff ic_encode_rgb2ycbcr_601 = { >> .coeff = { >> - { 77, 150, 29 }, >> + { 77, 150, 29 }, >> { 469, 427, 128 }, >> { 128, 405, 491 }, > We could subtract 512 from the negative values, to improve readability.
Agreed.
> >> }, >> @@ -197,8 +199,11 @@ static const struct ic_csc_params ic_csc_rgb2ycbcr = { >> .scale = 1, >> }; >> >> -/* transparent RGB->RGB matrix for graphics combining */ >> -static const struct ic_csc_params ic_csc_rgb2rgb = { >> +/* >> + * identity matrix, used for transparent RGB->RGB graphics >> + * combining. >> + */ >> +static const struct ic_encode_coeff ic_encode_identity = { >> .coeff = { >> { 128, 0, 0 }, >> { 0, 128, 0 }, >> @@ -208,17 +213,25 @@ static const struct ic_csc_params ic_csc_rgb2rgb = { >> }; >> >> /* >> - * R = (1.164 * (Y - 16)) + (1.596 * (Cr - 128)); >> - * G = (1.164 * (Y - 16)) - (0.392 * (Cb - 128)) - (0.813 * (Cr - 128)); >> - * B = (1.164 * (Y - 16)) + (2.017 * (Cb - 128); >> + * Inverse BT.601 encoding from YUV full range to RGB full range: >> + * >> + * R = 1. * Y + 0 * (Cb - 128) + 1.4020 * (Cr - 128) >> + * G = 1. * Y - .3442 * (Cb - 128) - 0.7142 * (Cr - 128) > Should that be ^^^^^ .3441 and ^^^^^ .7141 ? > The coefficients and offsets after rounding should end up the same.
Ok.
> > Also, let's consistently either add the leading zero, or leave it out.
Yes.
> >> + * B = 1. * Y + 1.7720 * (Cb - 128) + 0 * (Cr - 128) >> + * >> + * equivalently (factoring out the offsets): >> + * >> + * R = 1. * Y + 0 * Cb + 1.4020 * Cr - 179.456 >> + * G = 1. * Y - .3442 * Cb - 0.7142 * Cr + 135.475 >> + * B = 1. * Y + 1.7720 * Cb + 0 * Cr - 226.816 >> */ >> -static const struct ic_csc_params ic_csc_ycbcr2rgb = { >> +static const struct ic_encode_coeff ic_encode_ycbcr2rgb_601 = { >> .coeff = { >> - { 149, 0, 204 }, >> - { 149, 462, 408 }, >> - { 149, 255, 0 }, >> + { 128, 0, 179 }, >> + { 128, 468, 421 }, >> + { 128, 227, 0 }, >> }, >> - .offset = { -446, 266, -554 }, >> + .offset = { -359, 271, -454 }, > These seem to be correct. Again, I think this would be easier to read if > the negative coefficients were written with a sign as well. > >> .scale = 2, >> }; >> >> @@ -228,7 +241,7 @@ static int init_csc(struct ipu_ic *ic, >> int csc_index) >> { >> struct ipu_ic_priv *priv = ic->priv; >> - const struct ic_csc_params *params; >> + const struct ic_encode_coeff *coeff; >> u32 __iomem *base; >> const u16 (*c)[3]; >> const u16 *a; >> @@ -238,26 +251,26 @@ static int init_csc(struct ipu_ic *ic, >> (priv->tpmem_base + ic->reg->tpmem_csc[csc_index]); >> >> if (inf == IPUV3_COLORSPACE_YUV && outf == IPUV3_COLORSPACE_RGB) >> - params = &ic_csc_ycbcr2rgb; >> + coeff = &ic_encode_ycbcr2rgb_601; >> else if (inf == IPUV3_COLORSPACE_RGB && outf == IPUV3_COLORSPACE_YUV) >> - params = &ic_csc_rgb2ycbcr; >> + coeff = &ic_encode_rgb2ycbcr_601; >> else if (inf == IPUV3_COLORSPACE_RGB && outf == IPUV3_COLORSPACE_RGB) >> - params = &ic_csc_rgb2rgb; >> + coeff = &ic_encode_identity; >> else { >> dev_err(priv->ipu->dev, "Unsupported color space conversion\n"); >> return -EINVAL; >> } >> >> /* Cast to unsigned */ >> - c = (const u16 (*)[3])params->coeff; >> - a = (const u16 *)params->offset; >> + c = (const u16 (*)[3])coeff->coeff; >> + a = (const u16 *)coeff->offset; > This looks weird to me. I'd be in favor of not renaming the type.
Ok.
Steve
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