VirtualDub - Beginner's Guides / Tutorials?

[terrypin]

OK thanks. Sorry for the mis-quoting. So, I think I have it straight, but I'll summarise just in case:

1. Although the DivX spec is far more tolerant, you recommend that files presented to VirtualDub for compressing should be 'mod 16' in both dimensions.

2. Getting the files to meet that requirement could be accomplished in various ways.

a) When captured (e.g. in my case, sizing the Google Earth window - or more accurately the monitor view window, which is trickier) before running FRAPS. Presumably, that's always the preferred approach?

b) With AviSynth (which I don't have, but aim to investigate).

c) With VirtualDub in a preliminary session.

It does have a crop facility, I discovered earlier. But I'd never have known if I hadn't stumbled upon a thread about it. You use Video|Filters|Add|null transform and then use the cropping button. However, I'm finding it very awkward to use.
- Large images are impossible to adjust; see my recent post 'Novice: VirtualDub cropping & window sizes'. (The author confirmed some bugs.)
- You apparently have to calculate 4 offsets, X1, X2, Y1, Y2, which apply borders of those sizes to each side. No figures are shown before or while doing this. Cropping to me has always been a simple matter of dragging by visual inspection, or specifying a required WxH and then dragging that to position. The latter would be ideal in this case. By contast, in VirtualDub I have to first use File|File Information to tell me the size of my source: 840 x 598. I choose to make that 832, divisible by 16. I then decide on a 16:9 aspect ratio, as I eventually want to show this on my new TV. That implies 832 x 468. To make that last figure divisible by 16, I therefore settle on a target size of 832 x 480 (1.73 versus the ideal 1.78 ratio). So I calculate X1=X2=(840-832)/2= 4 pixels to be removed from left and right. And Y1=Y2=(598-480)/2= 59 pixels to be removed from top and bottom. Pretty long-winded really.

I've just processed that. (I managed to reach the OK button to start it, by removing my XP tool bar. I suppose I could have instead changed my desktop resolution from its normal 1024x768 to a larger size.) But I see to my surprise that my 344MB source file has become about 3GB. Why so enormous? Surely it should be smaller after cropping, not 9 times larger?

--
Terry, West Sussex, UK

[Abond]

I think this tool can be of some interest for you:
http://forum.doom9.org/showthread.php?t=101070&highlight=PARanoia

[terrypin]

Thanks, I'll take a look.

--
Terry, West Sussex, UK

[guns1inger]

terrypin : when you saved out your cropped version, did you select a codec and configure compression levels (bitrate or quality level, depending on codec) ?

[terrypin]

terrypin : when you saved out your cropped version, did you select a codec and configure compression levels (bitrate or quality level, depending on codec) ?

No. I'd understood from the discussion up-thread that I had to get my source file resized before I did the compression. Was I wrong?

I've since done the DivX compression on that 3GB file and it's back to about 12MB. That's rather larger than the earlier compression I did from the uncropped file, but I did also arbitrarily set bitrate to 1000 instead of the 780 default I've been using previously.

--
Terry, West Sussex, UK

[guns1inger]

Once you have set up all your filters in vdub, the final step is to save it out - this is where you can set your compression levels etc to save you having to do it later. This will be applied after the filters.

[jagabo]

terrypin : when you saved out your cropped version, did you select a codec and configure compression levels (bitrate or quality level, depending on codec) ?

No. I'd understood from the discussion up-thread that I had to get my source file resized before I did the compression. Was I wrong?

All you have to do is resize/crop before SAVING the file -- that's when Divx will compress it. That is, the output frame size in VirtualDub has to meet the codec's requirements, not the input size.

So you can crop/resize before VirtualDub receives the file using AVISynth (which is a little faster and slightly better quality), or you can do it all within a single session of VirtaulDUb.

[terrypin]

Thanks, penny now dropped! Didn't realise I could do both in one go.

--
Terry, West Sussex, UK