[mythtv-users] How can I tell the native X/Y size of a recorded file?

Mark Knecht markknecht at gmail.com
Mon Apr 7 19:34:08 UTC 2008

On Mon, Apr 7, 2008 at 7:56 AM, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 04/07/2008 10:27 AM, Mark Knecht wrote:
>  > Assume I've already recorded some material and the file resides on my
>  > backend server. How can I tell what the native X/Y video size of that
>  > file is?
>  >
>  mplayer -v -v -v -v -nolirc -nojoystick \
>         -vo null -ao null -frames 1 \
>         -identify '/path/to/recording.mpg' 2>&1 |
>  tee ~/mplayer_identify_output
>  You'll get a ton of output, but really the important stuff is at the
>  bottom.  The above will throw a copy of the output into a file so you
>  can browse through it more easily (especially if you don't have a big
>  scroll buffer in your terminal).
>  > I'm assuming that to reduce the CPU usage on the frontend that is
>  > displaying this file it would be better if I didn't rescale the
>  > recorded file but actually set the resolution of the display screen to
>  > the same resolution. Is this true?
>  If you're using Xv or XvMC, scaling if basically free as it's done by
>  the GPU.
>  >  If so I'd like to try two things:
>  >
>  > 1) Playing the file full screen after resetting X to run at that
>  > resolution. (If possible)
>  >
>  > 2) Start mythfrontend with --geometry set to those values.
>  >
>  > Just wanted to try an experiment to see how it impacts CPU usage.
>  If you do want to set Myth to output the video's native size, you should
>  set it up to use Xrandr, then it will switch automatically.  Of course
>  this means that your TV's scaler will be used instead.  IMHO, this is a
>  bad thing since you have 0 control over the TV's scaler, but you have a
>  lot of control over Myth's.
>  Mike

Mike & Steven,
   Thanks for the responses. I guess there's no way to do this from
within Myth itself? Seems like it might be a sort of useful feature
for the future to have some way of showing the user what Myth knows
about the data it's working with, if only down on some info page.

   I'll give the commands a try when I get access to the machine. In
the meantime I'll have to check out what sort of acceleration I can
make work on all of these front end machines. The most used machines
use a chipset based graphics controller from ATI and drive an S-video
output. This has limited me to older kernels and older ati-driver
packages as the chipset didn't gain much favor and apparently got
dropped from newer ATI packages. Bummer.

   I've never found an open source based replacement driver that
correctly supports the S-video output. Bummer #2.

   Anyway, thanks very much for the info.


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