V4L/DVB (13121): gspca - pac7311: add comment about JPEG header
Add comment about the meaning of the fixed JPEG header bytes used to
create each image.
Signed-off-by: Marton Nemeth <nm127@freemail.hu>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/gspca/pac7311.c b/drivers/media/video/gspca/pac7311.c
index b21c5e1..f954900 100644
--- a/drivers/media/video/gspca/pac7311.c
+++ b/drivers/media/video/gspca/pac7311.c
@@ -801,13 +801,32 @@
sd->autogain_ignore_frames = PAC_AUTOGAIN_IGNORE_FRAMES;
}
+/* JPEG header, part 1 */
static const unsigned char pac7311_jpeg_header1[] = {
- 0xff, 0xd8, 0xff, 0xc0, 0x00, 0x11, 0x08
+ 0xff, 0xd8, /* SOI: Start of Image */
+
+ 0xff, 0xc0, /* SOF0: Start of Frame (Baseline DCT) */
+ 0x00, 0x11, /* length = 17 bytes (including this length field) */
+ 0x08 /* Precision: 8 */
+ /* 2 bytes is placed here: number of image lines */
+ /* 2 bytes is placed here: samples per line */
};
+/* JPEG header, continued */
static const unsigned char pac7311_jpeg_header2[] = {
- 0x03, 0x01, 0x21, 0x00, 0x02, 0x11, 0x01, 0x03, 0x11, 0x01, 0xff, 0xda,
- 0x00, 0x0c, 0x03, 0x01, 0x00, 0x02, 0x11, 0x03, 0x11, 0x00, 0x3f, 0x00
+ 0x03, /* Number of image components: 3 */
+ 0x01, 0x21, 0x00, /* ID=1, Subsampling 1x1, Quantization table: 0 */
+ 0x02, 0x11, 0x01, /* ID=2, Subsampling 2x1, Quantization table: 1 */
+ 0x03, 0x11, 0x01, /* ID=3, Subsampling 2x1, Quantization table: 1 */
+
+ 0xff, 0xda, /* SOS: Start Of Scan */
+ 0x00, 0x0c, /* length = 12 bytes (including this length field) */
+ 0x03, /* number of components: 3 */
+ 0x01, 0x00, /* selector 1, table 0x00 */
+ 0x02, 0x11, /* selector 2, table 0x11 */
+ 0x03, 0x11, /* selector 3, table 0x11 */
+ 0x00, 0x3f, /* Spectral selection: 0 .. 63 */
+ 0x00 /* Successive approximation: 0 */
};
/* this function is run at interrupt level */