Hi Laurent,
On Thu, Apr 14, 2022 at 05:20:14PM +0300, Laurent Pinchart wrote:
> Hi Michael,
>
> Your previous mail slipped through the cracks, sorry about that.
>
> On Wed, Mar 02, 2022 at 12:00:12PM +0100, Michael Rodin wrote:
> > Hi Laurent,
> >
> > thank you for your work!
> >
> > On Mon, Feb 28, 2022 at 02:00:58PM +0200, Laurent Pinchart wrote:
> > > From: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> > >
> > > The vertical subsampling factor is currently not considered in the
> > > offset calculation for plane cropping done in rpf_configure_partition.
> > > This causes a distortion (shift of the color plane) when formats with
> > > the vsub factor larger than 1 are used (e.g. NV12, see
> > > vsp1_video_formats in vsp1_pipe.c). This commit considers vsub factor
> > > for all planes except plane 0 (luminance).
> > >
> > > Fixes: e5ad37b64de9 ("[media] v4l: vsp1: Add cropping support")
> > > Signed-off-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> > > Signed-off-by: LUU HOAI <https://urldefense.proofpoint.com/v2/url?u=http-3A__hoai.luu.ub-40renesas.com&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=sWsgk3pKkv5GeIDM2RZlPY8TjNFU2D0oBeOj6QNBadE&m=XAmHpGpli5fGaRsYAxJsReuojH4FFIzGmp2Njkwt8ko&s=l9CsK_BwOB0w3jdi3p2OFRTiGdlxWl2EHtxac3eVSTU&e=>
> > >
> > > Drop generalization of the offset calculation to reduce the binary size.
> >
> > Dropping generalization which I have done in my initial patch [1] is ok as
> > long as this will not cause any troubles. I am not aware of any case where
> > bytesperline and bpp could be different between the chroma planes, so
> > probably it's fine.
> >
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@xxxxxxxxxxxxxxxx>
> > > ---
> > > drivers/media/platform/vsp1/vsp1_rpf.c | 6 +++---
> > > 1 file changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/media/platform/vsp1/vsp1_rpf.c b/drivers/media/platform/vsp1/vsp1_rpf.c
> > > index 85587c1b6a37..75083cb234fe 100644
> > > --- a/drivers/media/platform/vsp1/vsp1_rpf.c
> > > +++ b/drivers/media/platform/vsp1/vsp1_rpf.c
> > > @@ -291,11 +291,11 @@ static void rpf_configure_partition(struct vsp1_entity *entity,
> > > + crop.left * fmtinfo->bpp[0] / 8;
> > >
> > > if (format->num_planes > 1) {
> > > + unsigned int bpl = format->plane_fmt[1].bytesperline;
> > > unsigned int offset;
> > >
> > > - offset = crop.top * format->plane_fmt[1].bytesperline
> > > - + crop.left / fmtinfo->hsub
> > > - * fmtinfo->bpp[1] / 8;
> > > + offset = crop.top / fmtinfo->vsub * bpl
> > > + + crop.left / fmtinfo->hsub * fmtinfo->bpp[1] / 8;
> >
> > Probably it makes sense to do the division after all multiplications are
> > done in order to avoid rounding errors? Consider the case when left = 3,
> > hsub = 2, bpp = 32. Then we would get for the second part of the offset:
> > 3 / 2 * 32 / 8 = 1 * 32 / 8 = 4
> > and if we do division as the last operation:
> > (3 * 32) / (8 * 2) = 96 / 16 = 6
>
> This was actually done on purpose :-) If the horizontal subsampling
> factor is equal to 2, for instance for the NV12 chroma plane, the
> horizontal offset must effectively be a multiple of 2. Otherwise you'll
> swap the Cr and Cb components.
>
> Taking your above example with a NV12 format (left=3, hsub=2, but
> bpp=16), with the rounding in this patch,
>
> offset = crop.top / fmtinfo->vsub * bpl
> + crop.left / fmtinfo->hsub * fmtinfo->bpp[1] / 8;
> = [vertical offset]
> + 3 / 2 * 16 / 8;
> = [vertical offset]
> + 2;
>
> Byte: 0 1 2 3 4 5
> Cr Cb Cr Cb Cr Cb ...
> ^
> offset
>
> With your rounding proposal,
>
> offset = crop.top / fmtinfo->vsub * bpl
> + (crop.left * fmtinfo->bpp[1]) / (fmtinfo->hsub * 8);
> = [vertical offset]
> + (3 * 16) / (2 * 8);
> = [vertical offset]
> + 3;
>
> Byte: 0 1 2 3 4 5
> Cr Cb Cr Cb Cr Cb ...
> ^
> offset
Thank you very much for the clarification, I have missed this point!
Now the patch looks fine to me.
Reviewed-by: Michael Rodin <mrodin@xxxxxxxxxxxxxx>
> > The first part of the offset can probably also cause the same rounding
> > issue.
> >
> > > mem.addr[1] += offset;
> > > mem.addr[2] += offset;
> > > }
> > >
> >
> > [1] https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_all_1637679566-2D76975-2D1-2Dgit-2Dsend-2Demail-2Dmrodin-40de.adit-2Djv.com_T_&d=DwICaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=sWsgk3pKkv5GeIDM2RZlPY8TjNFU2D0oBeOj6QNBadE&m=XAmHpGpli5fGaRsYAxJsReuojH4FFIzGmp2Njkwt8ko&s=zwktftJ_aVV0iA0D8dcfCy1_rRg5PSdi5OXfTZBs648&e=
>
> --
> Regards,
>
> Laurent Pinchart
--
Best Regards,
Michael
