[FFmpeg-user] Problem with ffmpeg psnr calculate filter when image file applied

[肖谋]

Because i would like to calcuate the psnr of two images and ffmpeg is my
favourite tool, :)


On Thu, Dec 19, 2013 at 2:28 PM, anshul <anshul.ffmpeg at gmail.com> wrote:

> On 12/18/2013 11:49 PM, Stefano Sabatini wrote:
>
>> On date Tuesday 2013-12-17 22:35:55 +0800, 肖谋 wrote:
>>
>>> Dear all,
>>>     I would like to calculate the PSNR of two images or two videos. I
>>> found
>>> that the new psnr filter worked well for video files which have at less
>>> two
>>> frames, but not for one frame, or image files.
>>>
>>> ffmpeg version is 2.0.2
>>> generate the files to be compared
>>> two frames video: ./ffmpeg -i test.mkv -vframes 2 -vcodec libx264 -an
>>> frame2.mkv
>>> one frames video: ./ffmpeg -i test.mkv -vframes 1 -vcodec libx264 -an
>>> frame1.mkv
>>>
>>> this one does not work:
>>> ./ffmpeg -i test.mkv -vframes 1 -vcodec rawvideo -filter:v
>>> "movie=frame1.mkv,setpts=PTS-STARTPTS[main];[in][main]psnr=f=c.log" -f
>>> rawvideo -y /dev/null
>>>
>>> this one works:
>>> ./ffmpeg -i test.mkv -vframes 1 -vcodec rawvideo -filter:v
>>> "movie=frame2.mkv,setpts=PTS-STARTPTS[main];[in][main]psnr=f=c.log" -f
>>> rawvideo -y /dev/null
>>>
>>> This situation can also be reproduced using image files.
>>> I looked into the vf_psnr.c. The do_psnr is not called.
>>>
>>> I think this might be a bug for filter process? any suggestions to fix
>>> this?
>>>
>> Are you able to reproduce the problem with latest git (2.0.2 is a bit
>> old and we had some fixes which may be relevant).
>>
>> Also you could file a bug report.
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>>
> I have not seen the source code about the implementation of PSNR
> calculation
> but as far as I knew psnr is calculated by comaring original(no noise) and
>  lossy compressed(noise)
> image, I dont get why you are trying to calculate psnr of one frame
>
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