Hi Folks
I've been playing with libzbvi and the ivtv drivers. I found this does
not work straight off. The zbvi code asks the driver what its
capabilities are.
./capture --pal -v
[,..]
Querying current vbi parameters... success
VBI capture parameters supported: format 59455247 [GREY], 27000000 Hz, 1443
bpl, offs 248, F1 6...23, F2 318...335, flags 00000000
The library then uses this list of capabilities to determine how it
want to configure the capture. Here the 1443 bpl is the number of
bytes per line. It uses this for the capture setup, but before
actually passing this to ivtv it does a sanity check. This sanity
check want to see that the byes per line is even, which it is not, and
so then refuses to do anything.
Interestingly i found the following comment in the ivtv code:
// determine number of lines and total number of VBI bytes.
// A raw line takes 1443 bytes: 2 * 720 + 4 byte frame header - 1
// The '- 1' byte is probably an unused U or V byte. Or something...
It seems this -1 is causing a problem...
Anyway, i modified ivtv-driver.h and set VBI_RAW_SIZE to 1444 and
libzvbi is then happy. However i don't know what side affects this
will have. eg IVTV_DMA_VBI_BUF_SIZE seems to depend on this size
somehow and i guess it is used in other places.
Come the VBI experts please comment.
Thanks
Andrew
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