PNSR howto

[themoog]

Has anyone got a quick step by step on how to measure PNSR of a encoded h.264 file and the tools they use. For example I have a source .mov and want to get the subsequent PNSR from the re-encode where it might be say an .mp4 file.

Any help much appreciated

Neil

[poisondeathray]

easiest way is probably msu vqmt
http://compression.ru/video/quality_measure/video_measurement_tool_en.html

if you are encoding using x264, --psnr will enable the PSNR calculation . It also has a --tune psnr tuning preset (tuning for PSNR usually gives lower visual quality, although higher PSNR metrics, because PSNR isn't a very good indication of "quality")

avisynth has a pnsr comparison as well
http://avisynth.org/mediawiki/Compare

[themoog]

Thanks for the quick reply, however I've already tried MSU VQT and not having much luck,

Also not having much luck in avisynth but I think this is because I haven't really used it in the past... and I don't tho its recognising my video input files..... (.movs) in this case.

But looks like I'm on the right tracks so i will persevere with avisynth.....

Any tips for getting .MOVS working?

[poisondeathray]

MOV can be loaded through avisynth into MSU VQMT via an .avs, either with QTInput() or FFVideoSource() . Videos have to be in the same colorspace (QTInput will usually output YUY2 unless otherwise specified), so FFMS2 is the preferred input source filter

If you have quicktime or quicktime alternative installed, forcing it to use directshow may work, but directshow is unreliable

[themoog]

are the libraries, have you any practical examples? Sorry for being a plum

[poisondeathray]

http://code.google.com/p/ffmpegsource/
http://avisynth.org/mediawiki/Main_Page#New_to_AviSynth_-_start_here


You need to install avisynth, ffms2 plugin (put the .dll and .avsi in the avisynth plugins folder)

Create a 1 line script in notepad, save it, change the extension from .txt to .avs

e.g.

FFVideoSource("testmovie.mov")

That .avs can be loaded into MSU VQMT

[themoog]

so would this be a valid .avs script?

clip1=QTInput("c:\test1.mov")
clip2=QTInput("c:\test2.mov")
Compare(clip1, clip2, "YUV","c:\compare.log")

[poisondeathray]

I think that's ok, you can preview the script in avspmod or vdub

QTSource.dll is external plugin (put in plugins folder to autoload)
http://www.tateu.net/

The benefit of MSU VQMT is you have graphs to look at. It's a bit more fancy, but you can just as easily plot the data from avisynth's compare in excel or similar software

[themoog]

Ok with MSU VQMT is there anyway to trick the free version into checking a HD version with a frameserve? Even with just a rough test? I think I see how it all works now

[themoog]

Ok i think I'm there I used the ReduceBy2() Function I'm all good.... Thanks for all your help