[mythtv] Adding raw VBI support for MPEG cards in setup
starz909 at yahoo.com
Sun Dec 2 02:45:03 UTC 2007
I'm wondering if it would be feasible to modify the
mythtv-setup program, specifically the capture card
page, to include an extra choice for hardware mpeg
cards. It would be, just like in your analog V4L card
setup page (but optional), an option to use the raw
VBI device node for playback and capture with the mpeg
It would be an optional override (disabled by default)
that would let mythtv know to check this device node
(such as /dev/v4l/vbi1) for all VBI data instead of
checking for it in the mpeg stream. The reason for
this is that many drivers for hardware capture cards
have incomplete or missing support for slicing VBI
data into the mpeg stream, such as IVTV (support is
not quite where it should be yet, as I hear) and
Blackbird (totally missing) drivers.
I have checked for myself, and have determined that
all the device nodes can be accessed simultaneously,
so there is no problem with the card(s) denying access
to one node when a different one is in use.
Furthermore, in the event that a card begins streaming
the uncompressed analog/vbi data at a different time
than when it begins to stream the mpeg, there could be
a buffer or delay control for the VBI that could be
added so the streams can be synchronized (disabled by
default as well of course).
I'm not too sure, but if someone then wanted to record
a program from the mpeg stream and include the vbi
data, would they require an extra encoding process to
splice the vbi data into the file?
If that's what it takes, I would gladly pay for the
extra cpu processing so everyone can obtain working
If it doesn't take much to merge the vbi stream into
the mpeg stream, all the better.
I'd gladly help test any patches or SVN revisions
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