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Due to a documentation bug (the type mask is 3 bits long, not 2) the wrong frame types were filled in: the B and P frame types were swapped. This bug also hid a second bug: when a capture is stopped a last entry is written into the pgm index buffer with internal type 0, denoting the end of the program. This entry wasn't ignored, instead it was accidentally returned to the caller as a P frame. Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org> |
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| .. | ||
| fw-calling.txt | ||
| fw-decoder-api.txt | ||
| fw-decoder-regs.txt | ||
| fw-dma.txt | ||
| fw-encoder-api.txt | ||
| fw-memory.txt | ||
| fw-osd-api.txt | ||
| fw-upload.txt | ||
| README.hm12 | ||
| README.vbi | ||
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>