[mythtv-users] How to use ivtv raw YUV framebuffer?

[Joseph A. Caputo]

zoiks2004-ivtv at yahoo.com wrote:

>I'm not sure if this belongs in mythtv-users or ivtv
>mailing lists, but in any case here's the question:
>
>How can I use the raw frame capture function of my
>PVR-350 within myth?
>
>This is what I've done:
>
>1) Changed the ivtv module loading to add the option
>"yuv_fixup=1".  Apparently, this is needed by ivtv to
>convert some wierd yuv format to standard yuv format.
>2) Tried dd'ing data from /dev/video32 and
>/dev/video24.  video32 is supposed to contain raw yuv
>data and video24 is supposed to have raw pcm audio
>data.  Each one reads just fine, I get like 10
>megabytes/s on video32 and around 160 kilobytes/s on
>video24.  Seems about right to me.
>3) I went into mythtv-setup and killed the PVR250/350
>capture card, and added another, a software V4L
>capture card.  I set the video device to /dev/video32
>and the audio device to /dev/video24.  I made sure my
>input connection showed V4L card SVideo 0 (the same
>input I use with the encoder) -> Comcast (my
>provider).
>4) I started mythtv and setup my recording profile for
>the software encoder (hardware encoder entry was gone)
>for mpeg4 encoding, otherwise using the default
>options.
>
>Now, when I try to play TV, myth hangs with lots of
>error messages.  A lot of "using protocol 15"
>interspersed with something like "couldn't set audio
>block size" or "couldn't set audio sampling".  Also
>some "couldn't read ringbuf.nuv" or some such.  I
>don't have the log files with me right now, but
>hopefully, if this is enough information, could
>someone tell me what I'm doing wrong?  I'd like to
>attempt direct frame capture encoding to mpeg4 using
>my PVR-350 card.
>
>My system:
>SuSE 9.2-based box with kernel 2.6.8
>ivtv-0.3.7b
>Myth 0.18.1
>2.4GHz P4 w/ 1 G RAM
>
>Any help greatly appreciated!
>  
>
My guess:  even though you're capturing 'raw' video & audio, it's still 
using the ivtv driver, not the V4L driver to read from those devices.
But, you've told Myth it's a V4L card.  Probably Myth is trying to use 
V4L ioctls on an ivtv card and it's choking.  Here's a good test:
trying firing up xawtv and pointing it to those video & audio devices 
and see what happens.  My guess is it won't work properly,
or maybe it will until you try to change a channel or something.

-JAC