[mythtv-users] FYI: pvrusb2 5 default minute recording sizes

Mike Isely isely at isely.net
Fri Aug 5 02:36:30 UTC 2005

I think I can shed some light on this, being that I'm the person who has
been working on the driver for the pvrusb2 device for the past 6 months...
See below.

On Thu, 4 Aug 2005, roger wrote:


> It looks as if the default 480x480 profile is being used, but mythtv is
> just recording @ 720 x 480 (the output resolution of /dev/v4l/video0).
> Which is just fine and dandy by me until I want to save disk space by
> reducing the resolution.

Video capture and encoding is handled entirely in hardware on this device.
By the time mythtv gets the data it's already an mpeg2 stream.  Therefore
the determination of encoding resolution happens in the device and right
now it's probably always going to do 720x480 for NTSC.

There are ioctl() controls in the driver which can be used to change the
capture resolution.  However this is a very immature driver and frankly
I'd be surprised if that part even worked - assuming that mythtv would
even know about or call those functions.  So you're probably stuck at

If you really want to store in 480x480 then you'd probably have to set up
mythtv to transcode after the fact.

> >From the looks of it, mythtv does not transcode while recording at the
> same time -- Or it is not possible with this hardware (external usb
> mpeg2 tv card)?  I can see however, mythtv will execute a
> script/transcode after recording has stopped.

Transcoding in mythtv happens in a second stage, after the recording is

Additional information on the pvrusb2 driver can be found at:



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