Comparing video files for quality

[Klagar]

Hi everyone !

I need to test extensively with different video formats, modes and particularities, especially videos converted with WinFF. The thing is, when comes the time to see if my video has improved (or not), I can't rely safely on my sole eyes ; only the best quality is permitted here, so I have to compare those videos as closely as I can, and I would vey much appreciate not having to rely on mere screenshots.

Is there a software that I can use to view two video files at the same time ? Or alternatively, is there another method I should consider ?

Thanks !

[Verify]

Perhaps you could open two instances of VLC player (which will play almost all formats) and arrange them side by side on your monitor - depending on the resolution of the files you might (or might not) be able to make a suitable comparison. It would also depend on the resolution of your monitor - it would help if it is 1920x1050 (or better). Or perhaps with the right vidio card and set-up you extend the desktop to two side by side monitors?

[guns1inger]

Using two players side by side often produces very different results because only one instance can use the hardware overlay feature, the second will not. If you have applied any adjustments to the overlay - colour/brightness/contrast etc - then the two displays will be very different.

If you are using WinFF then you are not doing this professionally (or at least, should not be), therefore your quest for highest quality is a personal one. I have no problem with this - quality is admirable. However if you cannot tell the difference between two pieces of encoded video, and you are the one who must be satisfied by the quality, then surely they are, for you intents and purposes, equal. There is no true objective measure of video quality. There are comparison tools - MSU has some - that will produce all sorts of numbers - but in the end it comes down to what you see and what pleases you. Video encoding is a series of compromises. File size, resolution, codec, bitrate. All of these are balanced to meet a set of requirements imposed either externally or internally to meet an end. Only you can tell if that balance meets your goal, and you tell by watching and being satisfied with the result, or being unsatisfied with the result.

[Klagar]

@guns1inger :
In fact, I am doing it professionally. I work for a company which products depend heavily upon FFmpeg, an even during my interview they made it clear that it would not change.

But you're not the first one telling me that WinFF is absolutely not the best software to use in this instance. Could you tell me what specificly you think is not optimal about it ? The encoding speed ? Only the quality ? Some PARTS of the quality ? Or maybe just the fact that it's open-source ? I doubt it, but it happens.

For now everyone here seems pretty content with the quality of the products, so I'll probably take this information into account for my sole personal gain, unless there is some major issue that can only be adressed by changing our methods. Note that although we publish HD movies, they are displayed on the web, so they don't require the same quality as a TV-destined product. Also we are not into some fancy artistic stuff. So maybe WinFF is okay-ish to suit our needs ? I'm very interested in your advice, and what you think would be a good replacement if we ever choose to try a new approach ?

As for my first question, there seems to be little ways to directly compare two videos, and maybe in my case the whole thing is simply pointless and I should rather focus in having just less heavy files ? I'm thinking out loud here, but still interested in any feedback.

Thanks again !

[jagabo]

You can use AviSynth's StackHorizontal() or StackVertical() to put two videos side-by-side. You can use the Subtract function to see the differences between the two. And Levels to amplify those differences. Here's one script that shows the two videos side-by-side, the differences, and the differences multiplied:

name1="video1.avi"
name2="video2.avi"

v1 = AviSource(name1)
v2 = AviSource(name2)
sub = v1.subtract(v2)
substrong = sub.levels(112,1,144,0,255)

StackVertical(StackHorizontal(v1.subtitle(name1),v 2.subtitle(name2)),StackHorizontal(sub.subtitle("D ifference"),substrong.subtitle("Difference amplified 8x")))

[PuzZLeR]

Greetings to my former town.

Is there a software that I can use to view two video files at the same time ? Or alternatively, is there another method I should consider ?

The best method, in my opinion, is using Avisynth and the "Interleave()" command, which grabs frames, one at a time, sequentially, in order of the clips in the parameter list.

When fed to an encoder it will create a project as such, but your interest is in previewing it, where you can compare the proposed project frame-by-frame, at your own pace, with the naked eye. You should notice any disparities in quality or details lost/retained between (two or more) video formats/files or this way.

Some formats may not be compatible with each other however, but in that case you can transcode to equivalent lossless versions of each and compare, or build a compensating script (depending on what is "incompatible").

And I agree with 'Slinger in that, nevertheless, regardless of your observations, especially in borderline situations, much of your final decision will also depend on compromise and relative metrics.

[PuzZLeR]

Hi Jagabo, we posted simultaneously with AviSynth advice. Hopefully they both prove helpful.

[jagabo]

Yes, I use Interleave() a lot too. Then I flip back and forth between the same frame in VirtualDub. And I use a screen magnifier to zoom in. Some other useful tools are the VideoScope() and Histogram() filters for adjusting levels. CSamp is good for scanning RGB values of pixels.

The above compare script produces:



A zoom utility (zoom box follows mouse cursor):


CSamp in action (mouse cursor was over the yellow ducky):


VideoScope() filter:

[Klagar]

Great ! That was exactly what I was looking for !
Haven't had the chance to try it out yet, but I'm confident it will prove the best solution !
Thank you so much !

And @ PuzZLeR : greetings to the town which has the most annoying hockey team ever hehehe...

[Klagar]

Ok I'm using AviSynth right now, and though adapting the script you gave to me took a little time, it was well worth it !
Yahooooooooo !!!

[lordsmurf]

@guns1inger :In fact, I am doing it professionally. I work for a company which products depend heavily upon FFmpeg, an even during my interview they made it clear that it would not change.

It's still amateur software.

I'm very interested in your advice, and what you think would be a good replacement if we ever choose to try a new approach ?

MainConcept Reference
Episode
Sorenson Squeeze

[Klagar]

Can you tell me why exactly it is considered amateur software ? Is it only quality-wise, or speed-wise, or something else, or all this AND something else ?

As a side note, I discovered we actually use a combination of WinFF and Sorenson Squeeze ; mainly because we start with products that Sorenson won't open, and the two softwares together seem to be working charmingly well... Not saying it's the best method in the world, but anyways...

[Xpenguin17]

MSU Video Quality Measurement Tool.

[jagabo]

MSU's video quality tool is useful for testing before/after compression. It won't help if you're filtering for restoration (ie, color correction, noise reduction, etc.).

[PuzZLeR]

Good post Jagabo regarding closer inspection.

For the record, I too have been doing something more when I want to really, really look at it. Assuming it's a 480 image, sometimes I use Crop(), with something like 180 pixels all around, and resize back to original:

Interleave(clip1,clip2,clip3,etc)
Crop(180,180,-180,-180)
LanczosResize(720,480)

Differences in detail become more lucid as such.

I've played around with zoom(), but I find it can take lots of trial and error before you position it where you want.

greetings to the town which has the most annoying hockey team ever

Granted. But, isn't it even more annoying when Montreal, in a drought of its own the last 17 years, has been significantly beaten by a pathetic team from Toronto in the overall standings/playoffs and in face-to-face meetings since?

That’s a low way to sink.

[Klagar]

Nice code bit, I'll make sur eto try it, and I'll let you know how it goes for me. Though I'm sure it'll come in handy.

Hehehe I can't argue regarding Montreal's poor performances lately.
And to think we just sent away the only good goaler we've had in years (Halak)...
I think we could talk long about how management sucks in this team !

[PuzZLeR]

Nice code bit, I'll make sur eto try it, and I'll let you know how it goes for me. Though I'm sure it'll come in handy.

If you are new to AviSynth, tools like MeGUI (Ctrl+R) and AvsP are excellent in setting up an intro script for you. Of course, for any MPEG-2 source you will need an indexed .d2v file beforehand (Ctrl+F2 in MeGUI) - easy to do.

If you want really simple, all you need do is set up a script with each video file, set a variable to each and load into Interleave(). Then preview it and just use left and right on your keyboard to compare frames.

A very simple example of an AVC .mkv file vs an MPEG-2 .mpg file (after indexed):

a=DirectShowSource("C:\avcfile.mkv")
b=DGDecode_mpeg2source("C:\mpeg2file.d2v")
Interleave(a,b)

Once you set it up once the first time, you can do the fancier stuff next. Let us know if you have questions.

I think we could talk long about how management sucks in this team !

Ahh, nothing can sink a team so low as the Harold Ballard era did here in Toronto - so bad that his stink is still around even today.