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V4L/DVB (9892): cx18: VBI comment corrections and comments about VBI issues

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VBI comment corrections to avoid future confusion about standards.
Comments on cx18 VBI implementation shortcomings that need resolution.

Signed-off-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Andy Walls 2008-12-14 19:21:35 -03:00 committed by Mauro Carvalho Chehab
parent 0ef0289264
commit aafc77066f
1 changed files with 12 additions and 4 deletions
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16
drivers/media/video/cx18/cx18-driver.c
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@ -609,18 +609,21 @@ static int __devinit cx18_init_struct1(struct cx18 *cx)
* We use a BT.656 pxiel clock of 13.5 MHz and a BT.656 active line
* length of 720 pixels @ 4:2:2 sampling. Thus...
*
* For NTSC:
* For systems that use a 15.734 kHz horizontal rate, such as
* NTSC-M, PAL-M, PAL-60, and other 60 Hz/525 line systems, we have:
*
* (1/15,734 kHz) * 2 * 13.5 MHz = 1716 samples/line =
* (1/15.734 kHz) * 2 * 13.5 MHz = 1716 samples/line =
* 4 bytes SAV + 268 bytes anc data + 4 bytes SAV + 1440 active samples
*
* For PAL:
* For systems that use a 15.625 kHz horizontal rate, such as
* PAL-B/G/H, PAL-I, SECAM-L and other 50 Hz/625 line systems, we have:
*
* (1/15,625 kHz) * 2 * 13.5 MHz = 1728 samples/line =
* (1/15.625 kHz) * 2 * 13.5 MHz = 1728 samples/line =
* 4 bytes SAV + 280 bytes anc data + 4 bytes SAV + 1440 active samples
*
*/
/* FIXME: init these based on tuner std & modify when std changes */
/* CX18-AV-Core number of VBI samples output per horizontal line */
cx->vbi.raw_decoder_line_size = 1444; /* 4 byte SAV + 2 * 720 */
cx->vbi.sliced_decoder_line_size = 272; /* 60 Hz: 268+4, 50 Hz: 280+4 */
@ -924,6 +927,11 @@ static int __devinit cx18_probe(struct pci_dev *dev,
}
cx->params.video_gop_size = cx->is_60hz ? 15 : 12;
/*
* FIXME: setting the buffer size based on the tuner standard is
* suboptimal, as the CVBS and SVideo inputs could use a different std
* and the buffer could end up being too small in that case.
*/
vbi_buf_size = cx->vbi.raw_size * (cx->is_60hz ? 24 : 36) / 2;
cx->stream_buf_size[CX18_ENC_STREAM_TYPE_VBI] = vbi_buf_size;