[pvrusb2] Setting bitrate in MythTV

Mike Isely isely at isely.net
Sun Mar 4 14:43:27 CST 2007

On Sun, 4 Mar 2007, Rod Smith wrote:
> It always goes like this:
> root at seeker:~# cat /sys/class/pvrusb2/sn-8605072/ctl_video_bitrate/cur_val
> 6000000
> 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).

Your theory sounds very plausible.  The "old" API was ivtv-specific and 
the pvrusb2 driver didn't make any attempt to implement it.  I had 
assumed that MythTV 0.20 implemented the new MPEG API, but maybe it does 
not.  If that is the case, then everything you've observed is explained.

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

The S/N ratio on that list is horrendous.  Or maybe it's better stated 
that the decibel level is so high that it's impossible to stay on top of 
any of it.  I did see your post there, but only because it surfaced when 
I searched my inbox for all occurences of "pvrusb2".  (I periodically do 
that to make sure something doesn't sneak by in constant incoming 


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