[MEncoder-users] [Script] PSNR between two video files

[Guillaume POIRIER]

Hi,

On 8/25/05, Matthias Wieser <mwieser at gmx.de> wrote:
> Hi,
> 
> I have created a script (called psnr-video.sh) to calculate the PSNR
> between two existing video files. The PSNR is calculated frame by frame.
> Additionally an overall PSNR is calculated.
> 
> The output file can be used for plots of the frame by frame PSNR.
> 
> "What's the purpose of this script, as there is already the mencoder
> option 'psnr'"?
> 
> mencoder [...]:psnr only shows the psnr of the video codec. Video filters
> like scaling, denoise3d, pp=fd cannot be tested with this option.
> 
> psnr-video.sh can be used to
> 
> * compare different softwarescalers (should I use -sws 1 or -sws 2)
> * compare different resolutions (is it better to scale down to 640x360 or
>    to 560x320)
> * compare different deinterlacers
> * compare different video codecs
> * compare video filters (is it better to use -vf hqdn3d or
>    lavcopts:nr=400)
> * [...]
> 
> Example:
> ./psnr-video.sh ./orig.avi ./test.avi 247
> 
> Creates a file psnr.dat with the following content:
> 
> File;Y;Cb;Cr
> 00000001.ppm;34.23;39.54;40.06;35.426
> 00000002.ppm;33.03;38.71;39.26;34.271
> 00000003.ppm;33.45;38.91;39.28;34.655
> 00000004.ppm;32.72;38.69;38.85;33.972
> [...]
> 00000247.ppm;35.55;40.84;42.15;36.785
> PSNR:;35.9887
> 
> -------
> 
> Usage: psnr-video.sh <file1> <file2> [<frames>] [<options1>] [<options2>]
> 
>  <file1> and <file2> are the video files for which the PSNR should be
>                      calculated.
>  [<frames>]          is the number of frames to process, starting from
>                      frame 1.
>  [<options1>]        are additional MPlayer options for <file1>
>  [<options2>]        are additional MPlayer options for <file2>
> 
>  Be aware that psnr-video.sh needs a lot of temporal space inside /temp/.
> 
> -------
> 
> Comments?

At first, I didn't quite understand how you were able to compute the
psnr of 2 pictures with only a shell script. Doing such thing in bash
would probably give you the "master of shell script" crown! :)
A quick glance at the code shows that you use the tool "pnmpsnr" to do
the frame-by-frame... so no crown for you today! ;o)


> If you find it usefull you may add it to [CVS]main/TOOLS/

I do. I'll add it tonight after some testing, only if nobody objects.

Guillaume

-- 
Reading doesn't hurt, really!
  -- Dominik 'Rathann' Mierzejewski