On Monday 25 August 2014 14:50:53 Philipp Zabel wrote:
> Hi Hans,
>
> Am Montag, den 25.08.2014, 13:38 +0200 schrieb Hans Verkuil:
> > Hi Philipp,
> >
> > I have to think a bit more about the format names, but in the meantime I
> > have
> > two other suggestions:
> Thank you, I haven't spent much thought about the actual descriptions
> yet. Most are just transcribed from the comments in videodev2.h without
> looking at the names used in the drivers.
>
> [...]
>
> > > +/**
> > > + * struct v4l2_pixfmt - internal V4L2 pixel format description
> > > + * @name: format description to be returned by enum_fmt
> > > + * @pixelformat: v4l2 pixel format fourcc
> > > + * @bpp_line: bits per pixel, averaged over a line (of the first plane
> > > + * for planar formats), used to calculate bytesperline
> > > + * Zero for compressed and macroblock tiled formats.
> > > + * @bpp_image: bits per pixel, averaged over the whole image. This is
> > > used to
> > > + * calculate sizeimage for uncompressed formats.
> > > + * Zero for compressed formats.
> >
> > I would add a 'planes' field as well for use with formats that use
> > non-contiguous planes.
>
> Good point, I'll add that.
>
> [...]
>
> > > +static inline unsigned int v4l2_bytesperline(const struct v4l2_pixfmt
> > > *fmt, + unsigned int width)
> > > +{
> > > + return width * fmt->bpp_line / 8;
> >
> > Round up: return (width * fmt->bpp_line + 7) / 8;
>
> Right, I should use DIV_ROUND_UP(width * fmt->bpp_line, 8) here.
>
> > > +}
> > > +
> > > +static inline unsigned int v4l2_sizeimage(const struct v4l2_pixfmt
> > > *fmt,
> > > + unsigned int width,
> > > + unsigned int height)
> > > +{
> > > + return width * height * fmt->bpp_image / 8;
> >
> > Ditto: return height * v4l2_bytesperline(fmt, width);
>
> I can't use v4l2_bytesperline because that might be zero for macroblock
> tiled formats and uses the wrong bpp value for planar formats with
> subsampled chroma.
>
> This nearly works:
> return height * DIV_ROUND_UP(width * fmt->bpp_image, 8)
Isn't that exactly height * v4l2_bytesperline(fmt, width) ?
> For the planar 4:2:0 subsampled formats and Y41P (bpp_image == 12),
> width has to be even, so that is ok.
> Most other formats have a bpp_image that is divisible by 8, but there
> are the 4:1:0 subsampled formats (bpp_image == 9). Those would round up
> width to a multiple of eight, even though it only has to be a multiple
> of four. I'd fall back to:
>
> if (fmt->bpp_image == fmt->bpp_line) {
> return height * DIV_ROUND_UP(width * fmt->bpp_image, 8);
> } else {
> /* we know that v4l2_bytesperline doesn't round for planar */
> return height * width * fmt->bpp_image / 8;
> }
Isn't that growing slightly too big for an inline function ?
--
Regards,
Laurent Pinchart
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