calculate the size to save

[Cazz]

Hi
I have maybe a very easy question but I have no idea what the answer is

Is that anyway I can calculate what is the minimum that the file have to be in X min in Xvid

I dont want to destroy that I have recording if I save it to small or have it unnecessary big file.

[jagabo]

Use target quantizer (~constant quality) encoding in Xvid. The file will come out exactly the size necessary for the quality you ask for.

[Cazz]

hmmm ok thanks

[guns1inger]

hmmm ok thanks

You don't seem convinced.

You have basically a choice when encoding. You can set a target size and aim for that, risking either compromising the quality (too small) or flooding the encoder (too big). Flooding the encoder does not effect quality, it just wastes space.

The second option is the one Jagabo has mentioned, which is to select a level of quality as the target, and let the encoder uses as much or as little space as it requires. The file sizes will vary based on many factors, including the amount of action and movement in the source, the amount of video noise in the source, and the level of quality you select.

If you have to fit a certain running time into a certain space, you use a bitrate calculator, then encode to that bitrate. However if space is not the issue, use the quality targets instead.

[Cazz]

I'm convinced and I'm very happy for all the help

I just try to understand how I can do that
I going to use virtualdub and sometime mencoder (Going to run in both Windows and Linux because I have two computer)

[guns1inger]

I don't know mencoder, so I can't help you there. For virtualdub it is a matter of selecting Video -> Full Processing Mode, then Video -> Compression. Select Xvid, and on the main screen, click on the button marked Target Bitrate (kbps). It should change to read Target quantizer. You can now play with various values to see what best suits your material. I suggest you try several values on a 5 minute representative sample. Start at around 3, and get smaller each time until you hit around 1.5. The smaller the value, the larger the file, but the closer to the original in quality it will be.

[Cazz]

ohh thanks

I think I have to use -q

example

-q 1.5

[guns1inger]

sounds about right