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

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>

1 files changed, 12 insertions, 4 deletions

diff --git a/drivers/media/video/cx18/cx18-driver.c b/drivers/media/video/cx18/cx18-driver.c
index 863ebf06a829..d7baf1b97cb8 100644
--- a/drivers/media/video/cx18/cx18-driver.c
+++ b/drivers/media/video/cx18/cx18-driver.c
@@ -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;