[mythtv] Relationship of XVideo to V4L

Michael J. Hammel mythtv at graphics-muse.com
Tue Jul 8 15:04:20 EDT 2003

I'm trying to figure out how to get an STB working with MythTV.  The TV
portion seems to work only through XVideo - XawTV and Zapping can view
TV but changing channels and setting audio has to be done externally.

MythTV seems to want to work with V4L devices.  My understanding is that
XFree86's v4l module will provide an Xv interface to V4l devices.  Is
that correct?  This assumes the TV is accessible through a V4l driver,
ie Xv sits atop V4L - is this also correct?

If I'm right about this, the only way to support my hardware would be

1. write a V4l driver for the TV hardware and make the X server not
manage that hardware


2. Add direct Xv support to MythTV

The latter seems easier to me since Xv is a pretty straight forward API
and I already know the X server is managing the TV hardware display (if
not specifically managing channels or audio - and that can be done at
the application level using vendor supplied tools anyway).  The former
I'm not sure how to do because I'm not sure what bit of hardware it is
I'm trying to write the driver for - is it just the SAA7114 tuner?  Or
does this *have* to go through the video controller stuff too?

I could use a pointer on how to get started here.  I've done plenty of
app level development (X/Motif/GTK+ based) but its been years since I've
done much hardware level stuff.

FYI, here is the hardware (all integrated on the motherboard) on the
system I'm working on:

   VIA C3(aka Samuel 2), 733/800MHz - CPU
   Trident CyberBlade/i1 - Video controller
   SAA7114 - Video decoder (Tuner)
   RealMagic 8470 - MPEG 2/4 decoder (Sigma Designs)
   VIA Tech VT8601 - PCI Bridge (AGP, NorthBridge)
   VIA VT82C686 - ACPI (SouthBridge)
   VIA VT82C686 AC97 - Audio controller
   Realtek RTL-8139/8139C (1 & 2) - Ethernet controllers

BTW, I have an updated trident.o (and source) from VIA that supports the
Cyberblade on this hardware.  I'm not sure if its the same one currently
in the XFree86 tree or not, however.
Michael J. Hammel <mythtv at graphics-muse.com>
Graphics Muse

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