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Commit 56f6f558 authored by Marton Nemeth's avatar Marton Nemeth Committed by Mauro Carvalho Chehab
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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: default avatarMarton Nemeth <nm127@freemail.hu>
Signed-off-by: default avatarJean-Francois Moine <moinejf@free.fr>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent 4fc8b648

drivers/media/video/gspca/pac7311.c

+22 −3
Original line number Diff line number Diff line
@@ -801,13 +801,32 @@ static void do_autogain(struct gspca_dev *gspca_dev) 
		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 */