# why does virtualdub create such large AVIs?



## m3wgz (Feb 23, 2009)

i used virtualdub to capture a vhs tape using _no compression_. this resulted in a 41gb file. i then used virtualdub to select 61% of the video so i could save that clip to a separate avi file. however, the resulting file size of that clip is 38gb! that leaves only 3gb for the remaining 39% that i didn't use and that makes no sense. mathematically, it should be a 25gb video file, not 38gb.

i am using no audio/video compression while trying to save this segment. i was under the impression that it would just save a lossless copy of the portion i selected. apparently it somehow adds even more data to the stream.

why is the file size so large?

note: i do not want to encode/compress this file. i want it to be lossless and uncompressed.


----------



## Jedi_Master (Mar 13, 2002)

Howdy m3wgz...

With out more info it's kinda hard to tell...

With video there are 2 sets of data that are saved 1 being video and the other being audio...

If the 39% you discarded contained little or no audio then that sounds about right...

I've been using virtual dub off and on for a while and haven't seen where it adds to the video being saved unless you change the video resolution...


----------



## m3wgz (Feb 23, 2009)

just now i captured 132mb of footage with my video capture card using virtualdub. both the audio and video are uncompressed. i then loaded that video into virtualdub, made sure audio and video compression were off, and selected "save as avi" from the file menu. that file is 198mb.

something is not right. i am sure i am not doing something i should be doing. any clues?


----------



## m3wgz (Feb 23, 2009)

HMMM... just now i loaded the 198mb file into vdub, saved it, and it produced a file of the same size! it has something to do with the capture then.

still, when i save a file using avidemux, it retains a much smaller file size. for example, in my op when i said the file size of the 41gb file should mathematically have been 25gb, avidemux actually produces a file that size.

i don't get it at all.


----------



## m3wgz (Feb 23, 2009)

nevermind.. i just figured it out. i was using a much higher bitrate on the new video files than the source file. i just discovered the option "direct stream copy" and my problems are solved.

case closed!


----------



## fairnooks (Oct 1, 2007)

Aww rats! You beat me to it! I was just going to say there never is a mystery in these things; its all about video dimension and bitrate over time, period.


----------

