diff options
author | Hans Verkuil <hverkuil@xs4all.nl> | 2006-08-26 05:00:12 -0300 |
---|---|---|
committer | Mauro Carvalho Chehab <mchehab@infradead.org> | 2006-09-26 12:30:34 -0300 |
commit | 299006612a811ba5acc92e2686f2e8b8bc10d4b7 (patch) | |
tree | d80813b510a850d1053500212d9c33eb5116b4df /Documentation/video4linux/cx2341x/README.vbi | |
parent | 784e8fe417d45b526eeb74794b7df43e11000f70 (diff) | |
download | linux-3.10-299006612a811ba5acc92e2686f2e8b8bc10d4b7.tar.gz linux-3.10-299006612a811ba5acc92e2686f2e8b8bc10d4b7.tar.bz2 linux-3.10-299006612a811ba5acc92e2686f2e8b8bc10d4b7.zip |
V4L/DVB (4547): Add YUV HM12 and VBI IVTV format documentation.
README.hm12: documentation on the HM12 YUV format used by the cx23415/6 chip.
README.vbi: documentation on the V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI format
used in MPEG streams.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Diffstat (limited to 'Documentation/video4linux/cx2341x/README.vbi')
-rw-r--r-- | Documentation/video4linux/cx2341x/README.vbi | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/Documentation/video4linux/cx2341x/README.vbi b/Documentation/video4linux/cx2341x/README.vbi new file mode 100644 index 00000000000..5807cf15617 --- /dev/null +++ b/Documentation/video4linux/cx2341x/README.vbi @@ -0,0 +1,45 @@ + +Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data +========================================================= + +This document describes the V4L2_MPEG_STREAM_VBI_FMT_IVTV format of the VBI data +embedded in an MPEG-2 program stream. This format is in part dictated by some +hardware limitations of the ivtv driver (the driver for the Conexant cx23415/6 +chips), in particular a maximum size for the VBI data. Anything longer is cut +off when the MPEG stream is played back through the cx23415. + +The advantage of this format is it is very compact and that all VBI data for +all lines can be stored while still fitting within the maximum allowed size. + +The stream ID of the VBI data is 0xBD. The maximum size of the embedded data is +4 + 43 * 36, which is 4 bytes for a header and 2 * 18 VBI lines with a 1 byte +header and a 42 bytes payload each. Anything beyond this limit is cut off by +the cx23415/6 firmware. Besides the data for the VBI lines we also need 36 bits +for a bitmask determining which lines are captured and 4 bytes for a magic cookie, +signifying that this data package contains V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data. +If all lines are used, then there is no longer room for the bitmask. To solve this +two different magic numbers were introduced: + +'itv0': After this magic number two unsigned longs follow. Bits 0-17 of the first +unsigned long denote which lines of the first field are captured. Bits 18-31 of +the first unsigned long and bits 0-3 of the second unsigned long are used for the +second field. + +'ITV0': This magic number assumes all VBI lines are captured, i.e. it implicitly +implies that the bitmasks are 0xffffffff and 0xf. + +After these magic cookies (and the 8 byte bitmask in case of cookie 'itv0') the +captured VBI lines start: + +For each line the least significant 4 bits of the first byte contain the data type. +Possible values are shown in the table below. The payload is in the following 42 +bytes. + +Here is the list of possible data types: + +#define IVTV_SLICED_TYPE_TELETEXT 0x1 // Teletext (uses lines 6-22 for PAL) +#define IVTV_SLICED_TYPE_CC 0x4 // Closed Captions (line 21 NTSC) +#define IVTV_SLICED_TYPE_WSS 0x5 // Wide Screen Signal (line 23 PAL) +#define IVTV_SLICED_TYPE_VPS 0x7 // Video Programming System (PAL) (line 16) + +Hans Verkuil <hverkuil@xs4all.nl> |