Re: [PATCH v5 07/10] media: Add parsing for APP14 data segment in jpeg helpers

[Mirela Rabulea]

Hi Philipp,
any thoughts on the jpeg helpers related patches from this patch set
(7,8,9,10)?

Thanks,
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
> 
>  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;
> +	int skip;
> +	int tf;
> +
> +	Lp = jpeg_get_word_be(stream);
> +	if (Lp < 0)
> +		return Lp;
> +
> +	/* 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.
>   */
>  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);