[mythtv] WinTV PVR-250 (hardware mpeg encoder)
Isaac Richards
mythtv-dev@snowman.net
Fri Jan 10 21:54:58 EST 2003
On Friday 10 January 2003 04:00 pm, kevin thayer wrote:
> So getting back to the original topic of this
> discussion (and the part that is interesting to me)
>
> Provided that v4l(v4l2?) compatible drivers were
> available for this card, would supporting its hardware
> encoding of mpg2 be:
>
> A) Fairly trivial, like that of mjpeg
> B) More complicated, along the lines of finding a good
> mpg2 decoding library and integrating that
Between A and B, but closer to B. Basically, to do it cleanly, there should
be a new pair of classes like NuppelVideoRecorder and NuppelVideoPlayer. The
new recorder class would be very lightweight, basically just grabbing the
encoded data from the card and pushing it to the ringbuffer class. The new
player class would just be a .mpg file format parser (could probably even
just use ffmpeg's libavformat), tying into the existing decoder/video
display/osd stuff. A bunch of code could be shared between the two sets of
classes and extracted out into a pair of base classes. All in all, a couple
days worth of work, as opposed to the couple hours it took for the mjpeg
stuff.
As for what the driver would need for mythtv, the best thing, IMO, would be
for it to use the same v4l ioctls for changing channels and inputs, etc, as
everything else does. The actual grabber stuff isn't as necessary to work in
the same fashion as the normal v4l code (like how the mjpeg stuff has an
extended ioctl set for grabbing the compressed frames), since that's probably
going to be custom code, anyway.
Isaac
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