From ddecbe112b057c333a8e055fb417451a02b9df78 Mon Sep 17 00:00:00 2001 From: Trent Piepho Date: Wed, 26 Jul 2006 17:08:29 -0300 Subject: V4L/DVB (4380): Bttv: Revert VBI_OFFSET to previous value, it works better A previous patch changed VBI_OFFSET to match what the datasheets say it should be. However, the bt8x8 datasheets are wrong. The old value of 244 is closer to what is actually observed. The real value appears to not be constant and is different for different chip revisions. Acked-by: Alan Cox Signed-off-by: Trent Piepho Signed-off-by: Mauro Carvalho Chehab --- drivers/media/video/bt8xx/bttv-vbi.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) (limited to 'drivers') diff --git a/drivers/media/video/bt8xx/bttv-vbi.c b/drivers/media/video/bt8xx/bttv-vbi.c index 8c9f0f7cf467..63676e7bd635 100644 --- a/drivers/media/video/bt8xx/bttv-vbi.c +++ b/drivers/media/video/bt8xx/bttv-vbi.c @@ -31,11 +31,16 @@ #include #include "bttvp.h" -/* Offset from line sync pulse leading edge (0H) in 1 / sampling_rate: - bt8x8 /HRESET pulse starts at 0H and has length 64 / fCLKx1 (E|O_VTC - HSFMT = 0). VBI_HDELAY (always 0) is an offset from the trailing edge - of /HRESET in 1 / fCLKx1, and the sampling_rate tvnorm->Fsc is fCLKx2. */ -#define VBI_OFFSET ((64 + 0) * 2) +/* Offset from line sync pulse leading edge (0H) to start of VBI capture, + in fCLKx2 pixels. According to the datasheet, VBI capture starts + VBI_HDELAY fCLKx1 pixels from the tailing edgeof /HRESET, and /HRESET + is 64 fCLKx1 pixels wide. VBI_HDELAY is set to 0, so this should be + (64 + 0) * 2 = 128 fCLKx2 pixels. But it's not! The datasheet is + Just Plain Wrong. The real value appears to be different for + different revisions of the bt8x8 chips, and to be affected by the + horizontal scaling factor. Experimentally, the value is measured + to be about 244. */ +#define VBI_OFFSET 244 #define VBI_DEFLINES 16 #define VBI_MAXLINES 32 -- cgit v1.2.1