Calculating Quality Factor

[marnix88]

Hello, is there a way to calculate the Quality Factor of a XviD video ?

I read somewhere that is has something to do with the bitrate and resolution. For example, GSpot says that the QF for a specific video is 0.194. How does it calculate that value?

Thanks.

[Manao]

It's the bit per pixel ratio. Basically, you divide the size of the video ( in bits ) by the number of pixels of the video ( hence width * height * number of frames ).

It's a rough indicator of the quality, and in fact it doesn't take into account the complexity of the video itself. Hence, with a bpp ( bit per pixel ) of 0.2, you can have a good looking video if the video was easy, or a block fest if it was hard. So in any case, your eyes will be a far better quality factor than bpp.

[marnix88]

Thanks a lot :)

But my calculation is not exactly the same as GSpot's.

GSpot info:
Size...........: 717480 KB
Resolution...:576 x 320
Frames.......: 140805
QF.............: 0.194

717480 KB = 5877600000 bits

576 * 320 * 140805 = 25953177600

5877600000 / 25953177600 = 0,22646937845483706781245931134074

Gspot = 0.194
My Calc = 0.226

Am I doing something wrong?

[Manao]

Ok, I should have mentionned it : the size of the video alone, without audio.

[marnix88]

Actually I should have thought about that myself.

Now I get the same result. Thank you, Manao :)