Hi Phipipp,
On Wed, 2020-12-02 at 16:18 +0100, Philipp Zabel wrote:
>
> Hi Mirela,
>
> On Thu, 2020-11-12 at 05:05 +0200, Mirela Rabulea (OSS) wrote:
> > From: Mirela Rabulea <mirela.rabulea@xxxxxxx>
> >
> > According to Rec. ITU-T T.872 (06/2012) 6.5.3
> > APP14 segment is for color encoding, it contains a transform flag,
> > which
> > may have values of 0, 1 and 2 and are interpreted as follows:
> > 0 - CMYK for images that are encoded with four components
> > - RGB for images that are encoded with three components
> > 1 - An image encoded with three components using YCbCr colour
> > encoding.
> > 2 - An image encoded with four components using YCCK colour
> > encoding.
> >
> > This is used in imx-jpeg decoder, to distinguish between
> > YUV444 and RGB24.
> >
> > Signed-off-by: Mirela Rabulea <mirela.rabulea@xxxxxxx>
> > ---
> > Changes in v5:
> > This was patch 8 in previous version
> > Replaced a struct for app14 data with just an int, since the
> > transform flag is the only meaningfull information from this
> > segment
>
> Could we turn this into an enum for the transform flag, and include
> the
> above spec reference in its kerneldoc comment? I think this would be
> better than checking for (app14_tf == <magic_number>) in the drivers.
Appreciate your feedback, for all patches, I'll address it in v6.
Where would be a better place for this enum, v4l2-jpeg.h, or maybe
include/uapi/linux/v4l2-controls.h?
Thanks,
Mirela
>
> > drivers/media/v4l2-core/v4l2-jpeg.c | 39
> > +++++++++++++++++++++++++++--
> > include/media/v4l2-jpeg.h | 6 +++--
> > 2 files changed, 41 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/v4l2-jpeg.c
> > b/drivers/media/v4l2-core/v4l2-jpeg.c
> > index 8947fd95c6f1..3181ce544f79 100644
> > --- a/drivers/media/v4l2-core/v4l2-jpeg.c
> > +++ b/drivers/media/v4l2-core/v4l2-jpeg.c
> > @@ -45,6 +45,7 @@ MODULE_LICENSE("GPL");
> > #define DHP 0xffde /* hierarchical progression */
> > #define EXP 0xffdf /* expand reference */
> > #define APP0 0xffe0 /* application data */
> > +#define APP14 0xffee /* application data for colour
> > encoding */
> > #define APP15 0xffef
> > #define JPG0 0xfff0 /* extensions */
> > #define JPG13 0xfffd
> > @@ -444,8 +445,37 @@ static int jpeg_skip_segment(struct
> > jpeg_stream *stream)
> > return jpeg_skip(stream, len - 2);
> > }
> >
> > +/* Rec. ITU-T T.872 (06/2012) 6.5.3 */
> > +static int jpeg_parse_app14_data(struct jpeg_stream *stream)
> > +{
> > + int ret;
> > + int Lp;
>
> Let's keep variables lower case.
>
> > + int skip;
> > + int tf;
> > +
> > + Lp = jpeg_get_word_be(stream);
> > + if (Lp < 0)
> > + return Lp;
>
> Should we check that Ap1 to 6 are actually "Adobe\0"?
>
> > + /* get to Ap12 */
> > + ret = jpeg_skip(stream, 11);
> > + if (ret < 0)
> > + return -EINVAL;
> > +
> > + tf = jpeg_get_byte(stream);
> > + if (tf < 0)
> > + return tf;
> > +
> > + skip = Lp - 2 - 11;
> > + ret = jpeg_skip(stream, skip);
> > + if (ret < 0)
> > + return -EINVAL;
> > + else
> > + return tf;
> > +}
> > +
> > /**
> > - * jpeg_parse_header - locate marker segments and optionally parse
> > headers
> > + * v4l2_jpeg_parse_header - locate marker segments and optionally
> > parse headers
> > * @buf: address of the JPEG buffer, should start with a SOI
> > marker
> > * @len: length of the JPEG buffer
> > * @out: returns marker segment positions and optionally parsed
> > headers
> > @@ -476,6 +506,9 @@ int v4l2_jpeg_parse_header(void *buf, size_t
> > len, struct v4l2_jpeg_header *out)
> > if (marker != SOI)
> > return -EINVAL;
> >
> > + /* init value to signal if this marker is not present */
> > + out->app14_tf = -EINVAL;
> > +
> > /* loop through marker segments */
> > while ((marker = jpeg_next_marker(&stream)) >= 0) {
> > switch (marker) {
> > @@ -519,7 +552,9 @@ int v4l2_jpeg_parse_header(void *buf, size_t
> > len, struct v4l2_jpeg_header *out)
> > ret = jpeg_parse_restart_interval(&stream,
> > &out-
> > >restart_interval);
> > break;
> > -
> > + case APP14:
> > + out->app14_tf =
> > jpeg_parse_app14_data(&stream);
> > + break;
> > case SOS:
> > ret = jpeg_reference_segment(&stream, &out-
> > >sos);
> > if (ret < 0)
> > diff --git a/include/media/v4l2-jpeg.h b/include/media/v4l2-jpeg.h
> > index ddba2a56c321..008e0476d928 100644
> > --- a/include/media/v4l2-jpeg.h
> > +++ b/include/media/v4l2-jpeg.h
> > @@ -100,10 +100,11 @@ struct v4l2_jpeg_scan_header {
> > * order, optional
> > * @restart_interval: number of MCU per restart interval, Ri
> > * @ecs_offset: buffer offset in bytes to the entropy coded
> > segment
> > + * @app14_tf: transform flag from app14 data
> > *
> > * When this structure is passed to v4l2_jpeg_parse_header, the
> > optional scan,
> > - * quantization_tables, and huffman_tables pointers must be
> > initialized to NULL
> > - * or point at valid memory.
> > + * quantization_tables and huffman_tables pointers must be
> > initialized
> > + * to NULL or point at valid memory.
>
> Unnecessary, unrelated change? I'd drop this.
>
> > */
> > struct v4l2_jpeg_header {
> > struct v4l2_jpeg_reference sof;
> > @@ -119,6 +120,7 @@ struct v4l2_jpeg_header {
> > struct v4l2_jpeg_reference *huffman_tables;
> > u16 restart_interval;
> > size_t ecs_offset;
> > + int app14_tf;
> > };
> >
> > int v4l2_jpeg_parse_header(void *buf, size_t len, struct
> > v4l2_jpeg_header *out);
>
> regards
> Philipp
