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);
--
2.17.1
