Suggestion for the "calc" bouton...

[Donald]

Hello everybody !

Sorry for my bad english I'm French. So, i have an idea about the 3 "calc" bouton in FFmpegX. We've got 3 one:

a)The first one adjust the bitrate to be able to make hold X minute on X Mo.
b) The second one calculate the best bitrate, according to the size window
c) the third one calculate how much time is OK according the selected bitrate and number of minute.

What i propose is that:
c) calculate "how much Mo is the movie if the best bitrate (bouton b) is employed according to the number of minute"

Is this a good idea ?
(french explication here: http://forum.carpo.org/viewtopic.php?t=604&start=10)

[major]

Yes, it's a good idea. I had already the project of adding a 4th calc button, now there will be a 5th one!

[Donald]

Cool !! I'm very happy because you think it is a good proposition
Maybe I'm even happier than you understood me !!

[Donald]

Can you say to us of what is going to consist the 4th button?

[major]

Calculate image size from bitrate

[fredmic (France)]

Hi from France again...

Major, I used your "IMG" button and I find strange results !

Examples :
I use 612 kbit/s for the bitrate
4:3 in Autosize -> IMG -> 368 x 288 -> ratio 1.27 (not 1.33 !)
16:9 in Autosize -> IMG -> 432 x 256 -> ratio 1.68 (not 1.78 !)
2.35:1 in Autosize -> IMG -> 496 x 224 -> ratio 2.21 (not 2.35 !)

I think theese ratios are wrong because you use a number multiple of 16 for both width and heigth... but I believed that only heigth needed that for correct encoding.

First, if you want to keep a multiple of 16 for height, I think the estimation given by the program should be afined. Look for the examples, if you're subtract 16 from each height, you obtain a result nearer to the aspect ratio wanted.
368 x 288 becomes 368 x 272 -> ratio 1.35 (near 1.33 !)
432 x 256 becomes 432 x 240 -> ratio 1.80 (near 1.78 !)
496 x 224 becomes 496 x 208 -> ratio 2.38 (near 2.35 !)

Second, I think it's possible to forget a number multiple of 16 for heigth (i'm wrong ?). In this case, when you obtain the width, you need only to multiply it by the ratio you want to obtain the heigth. And then you make an approximation to the nearest even number.

And, to finish, I suppose it would be safe to include the other ratios used in the cinema to complete the list.

The most important and famous ratios that you can find are :
4:3 (1.33:1)
5:3 (1.66:1)
16:9 (1.78:1)
1.85:1
2.35:1

Thx reading me.
"Vive ffmpegX" (long life to ffmpegX in french)

In this case, when you obtain the width, you need only to multiply it by the ratio you want to obtain the heigth. And then you make an approximation to the nearest even number.

to the nearest odd number... error of translation.

[major]

Hi, Thanks for your remarks.

I think theese ratios are wrong because you use a number multiple of 16 for both width and heigth... but I believed that only heigth needed that for correct encoding.

No, both width and height need that. Many codecs doesn't support a width or height not multiple of the macroblock size (or support but introduce errors or noise which will drastically reduce quality). This is especially true for XviD and libavc.

If you want to keep a multiple of 16 for height, I think the estimation given by the program should be afined. Look for the examples, if you're subtract 16 from each height, you obtain a result nearer to the aspect ratio wanted.

You're right here. I was rounding for bits per pixels accuracy, but it's indeed better to round for aspect ratio accuracy as you suggest. I published a new version fixing this (just download again ffmpegX 0.0.7d).

BTW if your source is D2 size, you should not use a width lower than 512 to avoid excessive quality drop.

[fredmic (France)]

You're right here. I was rounding for bits per pixels accuracy, but it's indeed better to round for aspect ratio accuracy as you suggest. I published a new version fixing this (just download again ffmpegX 0.0.7d).

Thank you for including this benefic change in the last release of ffmpegX. Keeping a multiple of 16 for the height is just a little problem if I want to respect exactly the ratio... but when the ratio is a little different from its origin... who can really see it ? Who cares ?

And, to finish, I suppose it would be safe to include the other ratios used in the cinema to complete the list.

The most important and famous ratios that you can find are :
4:3 (1.33:1)
5:3 (1.66:1)
16:9 (1.78:1)
1.85:1
2.35:1

Most of the cinema movies on DVD are in 1.85 (Panoramic) or 2.35 (Cinemascope)... so, can it be possible to add these formats, 1.66 and 1.85, to the list used by "Autosize" ?
Thx reading all of us and more ! -> Thx replying to our wishes...

[fredmic (France)]

bump ! just in case...

So, can we expect the 1.66 and 1.85 autosize including in the list ?

[major]

It's a good suggestion, I added it to my to-do list.