Resize video without re-encoding

[headless chicken]

How can you resize a video clip on a Mac without re-encoding the whole thing? I've got an avi which has been stretched to 16:9, but I know for a fact the original release was in 4:3. I'd like to restore the original aspect ratio without re-encoding but don't know how. The only way I can do this is with MPEG Streamclip, but I'd have to export to avi or mov. However, this solution does not work well for me because when I select the 5 min of the 50 min 200MB clip I want, the output is a 99MB file!

[guns1inger]

You can't resize video on any platform without re-encoding.

Regardless of platform or software, size is determined by bitrate. When you save out the portion of video you want to keep, set the correct bitrate for the size and running time.

For example, your running time is 5 minutes, your audio is 128 kbps, and you want to a file size of around 10 MB. Use a video bitrate of 145 kbps and you will meet the target size.

You do need to take into account that the higher the resolution, the higher the bitrate required to hold the quality, so resizing a video up while dropping the bitrate down is likely to result in a poorer quality output.

Streamclip should allow you to set the bitrate for your output.

FWIW, there is a windows app called mpeg4modifier that allows you to change the pixel aspect ratio attributes in (most) Divx/Xvid based avi files to fix problems like this without the need to re-encode. I don't know if there is a Mac equivalent, but you might be able to get a friend with a PC to make the changes for you.

If you haven't looked already, there is a good range of Mac video apps in the tools section : https://www.videohelp.com/tools?s=15#15

[Case]

You could 'play' with the width and height parameters in QuickTime Pro (Movie Properties, Video track, Visual settings, de-select Preserve aspect ratio). You can also cut away any segment not wanted. If you save as .mov then no re-encoding will be needed.

[headless chicken]

Thanks guns1inger. The mpeg4modifier app is what I was looking for. I do have a PC laptop, but I prefer the Mac OS now that I've grown accustomed to using it.

I suppose I'll just transfer the file I need modified over the home network and fire up the PC.

[headless chicken]

Didn't see your post there, Case. I've already trimmed the selection down, but I didn't know I could easily modify the aspect ratio in QT Pro. I'll check that out. Thanks!

[jpschuck]

Thanks guns1inger. The mpeg4modifier app is what I was looking for. I do have a PC laptop, but I prefer the Mac OS now that I've grown accustomed to using it.

There is a command line version of mpeg4modifier that runs on Mac OS X if you install the Mono framework. But... well... it runs in command line only...

[redrocklobster]

It would be great if someone could put together a tutorial for installing this command line version of mpegmodifier along with the mono framework. i just want to use it to get detailed info. unless there's another alternative that gives more info than VLC on Mac OS X.

maybe an answer is better in this thread:

https://forum.videohelp.com/viewtopic.php?p=1677034&sid=290db7fa0fe7295c9a8faed9c4d92ffe#1677034

(Sorry for double post on same issue)

[jpschuck]

It would be great if someone could put together a tutorial for installing this command line version of mpegmodifier along with the mono framework. i just want to use it to get detailed info. unless there's another alternative that gives more info than VLC on Mac OS X.

maybe an answer is better in this thread:

https://forum.videohelp.com/viewtopic.php?p=1677034&sid=290db7fa0fe7295c9a8faed9c4d92ffe#1677034

I gave you instructions for mpeg4modifier in the topic you mentioned, but please note that avidemux has a nice GUI and can give you almost the same informations as mpeg4modifier. You just need to install X11 first from your Mac OS X install disc if it is not already done.
http://fixounet.free.fr/avidemux/download.html

[redrocklobster]

FYI, now that I got these both to work (thanks again), the info given by avidemux & mpeg4modifier is very different. Different kinds of info are given, and in one case (4CC), they report different things entirely.

Avidemux 2 Info (typed by hand from file properties screen is there a way to put this info on the clipboard or save it?) :

FPS: 23.976
# of frames: 134059
Codec 4CC: DIVX
Aspect Ratio: 1:1
Packed Bitstream: No
Quarter Pixel: No
GMS: No
Audio Bitrate: 20000 Bps / 160 kbps
VBR: No

mpeg4modifier info:

Packed bitstream: No
QPel: No
GMC: No
Interlaced: No
Aspect ratio: Square pixels
Quant type: H.263
FourCC: XVID
User data: XviD0041

I-VOPs: 908 (0.68%)
P-VOPs: 132588 (98.91%)
B-VOPs: 0 (0.00%)
S-VOPs: 0 (0.00%)
N-VOPs: 553 (0.41%)