Need to resize Divx

[sync]

I recently bought an Oppo player for upscaling Divx to HDTV. The Oppo won't play files larger than 720x480. I have a bunch of files that are 960x544 that I want to downsize for use in the Oppo. The files have AC3 audio that I don't want to lose.

What tool is good for resizing Divx?

[jagabo]

VirtualDub, VirtualDubMod, AutoGK...

https://www.videohelp.com/guides.php?formatconversionselect=DivX+to+DivX

[sync]

Thanks. I like vdub and will check out how to use it for resizing.

I read that Divx works best on files with a resolution that is a multiple of 16. Can anyone suggest a formula for resizing that will maintain the aspect ratio and be a multiple of 16? Or is there an easier way to figure out the target size?

[jagabo]

Since your source is likely square pixel (16:9) and you're encoding to a normally square pixel codec, just keep the same ratio of width:height.

Try 704x400 or 640x360. The latter one isn't mod16 but the difference between mod16 and not mod16 is only a few percent in terms of bitrate/quality.

Since you probably don't care about the exact file size in a case like this, I recommend using Divx or Xvid in constant quality mode ("1-pass quality based" in Divx, "Single pass target quantizer" in Xvid). Pick the quality you want and encode.

The quality in this mode depends on the Quantizer value selected. Lower quantizers give higher quality and larger files, higher quantizers give lower quality and smaller files. Encode a short segment with different quantizers and see what you think.

At Q=2 there will be very little macroblocking (assuming you have a clean, macroblock free source) even if you look at enlarged still frames. Q=3 will give you a video that has slight macroblocking if you look at enlarged still frames but it won't be noticeable at normal playback speed. At Q=4 you might be able to see a little macroblocking at normal playback speeds if you look really closely. I usually use Q=3.

Quick VirtualDubMod instructions:

File -> Open Video File
Video -> Filters... -> Add... -> Resize (set width, height, Lanczos3 filter)
Video -> Compression... -> Divx or Xvid --> Configure... set parameters
File -> Save As...

[sync]

Thanks for the great tips.

I'm using Divx 6.1 and the 'Quality Based' section with the Target Quantizer is greyed out and can't be selected.

[jagabo]

I'm using Divx 6.1 and the 'Quality Based' section with the Target Quantizer is greyed out and can't be selected.

Are you using the free unregistered version? Maybe that's why.

[sync]

I'm using Divx 6.1 and the 'Quality Based' section with the Target Quantizer is greyed out and can't be selected.

Are you using the free unregistered version? Maybe that's why.

Yes. Until now I only used it for decoding. I guess it is time to get the paid version.

[jagabo]

I just tried installing the latest 6.5.1 release on a virtual PC and I was able to select single pass quality based encoding and to set the quantizer value, without registering. You might try updating to that version if you don't already have it.

[sync]

OK. Thanks a lot for all your help.