editing movies in vdub: how to get whole vid in memory?

[SignedupGuest]

I have 3GB of memory, is it possible to have vdub load up the whole video in memory?

[jagabo]

No. At least probably not in the sense you're thinking. You can open an AVI then preview it all or scrub through it slowly. That will cause Windows' disc cache to hold the entire file. But VirtualDub will continue to read compressed frames from the cache and decode them on an as-needed basis.

[SignedupGuest]

why not?

Wouldnt it be better and faster?

Besides, dont most people say you only need more memory if you do video editing?

[jagabo]

An hour of uncompressed RGB D1 video is 112 GB. That's why.

[SignedupGuest]

I dont work with uncompressed video

[manono]

Hehe, but VDub does.

[jagabo]

The process of viewing, editing, filtering, and compressing video involves decompressing the source so it can be worked with. For VirtualDub to load the whole video into memory for instant access it would have to decompress all the frames.

In theory it could load the entire video into memory in compressed form but this would make little difference to the seek speed (moving the seek bar or using the arrow keys). With short GOP material seeking to any random frame is fast enough reading from the disk (and as noted, Windows caches disk reads). With long GOP material the decoding of the GOP is the limiting factor and the cause of delays when seeking.

For filtering and compressing, having the entire source buffered in memory would make little difference in encoding speed. The filtering and compression take much longer than reading sequential frames from the disk.

[mpack]

why not?

Wouldnt it be better and faster?

Suppose your PC had the memory to buffer an entire uncompressed video: with your design VDub would read every compressed frame and decompress it to memory before allowing you to do anything. This would be a hell of a long wait every time you opened a video clip. I think most people would find that a tad painful to use. I wouldn't call it better, and I doubt your impression of it would be "faster".