diff options
| -rw-r--r-- | Documentation/media/v4l-drivers/cx2341x.rst | 50 | ||||
| -rw-r--r-- | Documentation/video4linux/cx2341x/README.vbi | 45 |
2 files changed, 50 insertions, 45 deletions
diff --git a/Documentation/media/v4l-drivers/cx2341x.rst b/Documentation/media/v4l-drivers/cx2341x.rst index 15bfd345df48..e06d07ebdecd 100644 --- a/Documentation/media/v4l-drivers/cx2341x.rst +++ b/Documentation/media/v4l-drivers/cx2341x.rst @@ -3806,3 +3806,53 @@ Raw format c example fclose(fin); return 0; } + + +Format of embedded V4L2_MPEG_STREAM_VBI_FMT_IVTV VBI data +--------------------------------------------------------- + +Author: Hans Verkuil <hverkuil@xs4all.nl> + + +This section 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: + +.. code-block:: c + + #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) + diff --git a/Documentation/video4linux/cx2341x/README.vbi b/Documentation/video4linux/cx2341x/README.vbi deleted file mode 100644 index 5807cf156173..000000000000 --- a/Documentation/video4linux/cx2341x/README.vbi +++ /dev/null @@ -1,45 +0,0 @@ - -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> |
