Reducing File Size By Reducing fps

[iknowkungfu]

Hey,

I'm trying to convert a 90MB file to around 50MB.

I know I can do this by reducing framerate without too great an impact.


Question is, how?

The video is currently 29.97 FPS.

I want to get it down to 14.985 FPS. (I think)


Thanks in advance all!

[yoda313]

Hello,

Don't you want to reduce the bitrate? If you lower the videobitrate you lower the filesize.

Kevin

https://www.videohelp.com/convert

[iknowkungfu]

Thanks Kev,

But, if I lower the bitrate, the resolution is reduced.

Its half an hour of video, with already low resolution.

I've got other files which are same/similar. These are 14.985 FPS and they maintain watchable resolution., and are roughly half the size

[mats.hogberg]

But, if I lower the bitrate, the resolution is reduced.

No, but the quality is reduced.
If you lower the frame rate (by taking out every odd frame for instance) it will only play on your computer, not as DVD, SVCD or VCD.

/Mats

[Suntan]

If you want to do it then open the file in Vdub and somewhere around the "Conversion" tab (sorry at work) there is a menu for frame rate. If memory serves you can decimate by 2 (IE 30=>15) or input the exact fps you want it to be.

Just be warned, you need to re-encode to do it so don't expect anywhere decent results if you want to re-encode your 90 meg 30 fps video to 50meg 15 fps. If you are starting with the original source and encode down to 50meg 15fps you should be fine.

-Suntan

[iknowkungfu]

Sorry, thats what I meant, just got confused.
(In traditional scientific terms resolution is what I meant)

I don't mind if it won't play back on anything else, because the other files are at 14.985 and will only be played/stored together - on a computer.

Thanks suntan, will give it a try, unfortunately I haven't got the source

Thanks mats, nice avatar btw

[mats.hogberg]

Thanks mats, nice avatar btw

Gee, I'm flattered! Spent a good portion of the weekend creating it, as my old one got misplaced in the server change, and I thought "Why not upgrade my avatar when I'm at it?" Thought it'd be faster than rummaging thru my computer innards, searcing for the old one, that must be here somewhere - I was wrong...

/Mats

[iknowkungfu]

Thats ok!

I have to admit, beyond simple muxing and copying I'm a complete newbie.

I have used VDub successfully in the past...

I've figured out how to change the fps, but how do I:

Keep the resolution
Know what the file size will be

Can't I just get VDub to copy the audio and the video but only re-encode every other frame?

[DRfrankenpimp]

the version of virtual dub i use has under frame rate a box to enter your new frame rate i just tried it and it reduced a 29 fps video to 14fps and reduced file size by half,decimating the video only gives you a slow motion look.if your version has the frame rate box then try it

[Suntan]

@iknowkungfu

If your video was uncompressed AVI or compressed with only I frames then yeah, you could just cut out every other frame, but as it is compressed certain frames (P, B) need info from the frames before it and after it to know what to "put on" so if you take those frames away you are left with a "naked" frame.

If you don't add a crop or resize filter then you will keep the resolution. If you want exact file sizes check out the guides here and on Doom9 for Xvid/Divx concerning the parts about "2 pass encoding"

-Suntan

[iknowkungfu]

Thanks all for the replies and the help, I figured it all out eventually!

This has been bugging me for so long!

Its nice to actually get a problem solved in the forums for once...

[mats.hogberg]

Its nice to actually get a problem solved in the forums for once...

What do you mean by that?!?

/Mats