[pvrusb2] Setting bitrate in MythTV

Rod Smith rodsmith at rodsbooks.com
Sun Mar 4 00:38:07 CST 2007

On Saturday 03 March 2007 23:31, Mike Isely wrote:
> On Sat, 3 Mar 2007, Rod Smith wrote:
> > Hi,
> >
> > I've discovered that my WinTV-PVR-USB2 doesn't respond to MythTV's
> > bitrate options. Checking the mailing list archives, I found a reference
> > to this limitation, but I was wondering if and when changing the bitrate
> > might be supported -- or if it should work, what software versions I need
> > to run. (I'm using the MythTV 0.20 delivered with Ubuntu 6.10 and a
> > locally-compiled 2.6.20 kernel with its pvrusb2 driver.) Thanks for any
> > pointers.
> The pvrusb2 driver implements the mpeg control API that Hans created
> last summer.  It's had this implemented since the API first appeared.
> So assuming that MythTV is controlling things correctly, then it
> _should_ be working.
> One thing you can do to check things a bit - after you think MythTV
> should have set your desired bit rate, use the pvrusb2 driver's sysfs
> interface to inspect the current bit rate.  It should match.

It always goes like this:

root at seeker:~# cat /sys/class/pvrusb2/sn-8605072/ctl_video_bitrate/cur_val

If I cat another value into cur_val, it stays at that value. It doesn't change 
when I change my MythTV recording profile -- and I *HAVE* set my recording 
profiles to use different bitrates, none of which is precisely 6000000. 
MythTV DOES set the bitrate correctly on another MPEG-2 encoding card (an 
AVerMedia AVerTV M150-D), but that's in a slave backend on another computer, 
so it's possible there's a problem just with the master backend to which my 
WinTV PVR-USB2 is connected. I also know nothing about the relevant APIs; 
does this new API you mention replace something older? If so, and if your 
driver doesn't implement the older API, it seems perfectly plausible that 
MythTV doesn't yet implement the new API (or at least, that the binary 0.20 
version I'm running doesn't).

I've also posted about this to the mythtv-users mailing list, but so far I've 
gotten no reply.

Rod Smith, rodsmith at rodsbooks.com
Author of books on Linux, FreeBSD, and networking

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