hello everyone, first of all i am new here, and i just wanted to post a question regarding when & how virtualdub processes frames when you choose the frame rate decimation option. i have been working on vid-capping some autocross videos from my camcorder and turning them into an SVCD. one of the steps i follow in that procedure involves using AVISynth's separate fields option, and Donald Graft's smart bob filter. obviously as a result of this i get a 59.94fps file as a result, so i need to decimate the frame rate by two to get it back to 29.97fps. what i would like to do, however, is to process some temporal-based filters on the 59.94fps file, before truncating every other frame after processing is done. what i am wondering, is does virtual dub process the frame rate decimation AFTER the filter chain? or BEFORE it. since i use a lossless compression codec ONLY up until the final MPEG2 encoding, disk space is pretty important, so i'd rather not have 3 copies of a 10 minute video lying around, and if VirtualDub does the frame rate decimation after the filter chain, i wont need to save the 59.94fps step (since it gets frameserved to virtualdub that way from a 29.97fps source), thereby saving A LOT of disk space (even if its temporarily). all i have is about 25GB of free disk space to work with (60GB drive, 40GB partition, and i DO like my games still ) originally when capturing i used lossy compression schemes, but i was finding so much quality degredation down the post-processing pipeline to the point where the final SVCD MPEG2 output looked no better than a VCD MPEG1 clip! i have used a short 4 minute clip and a cd-rw to test how using lossless compression affects the final outcome--MUCH, MUCH better, to say the least. such a shame too, because i have enough processor speed to do an xvid 1-pass quality encode at 85% quality in real time with about 25% of cpu to spare, really helped with disk space, but post-process filtering and recompression just amplified the original compression artifacts
you may also want to post this question at: http://virtualdub.everwicked.com/index.php some very clever vdub fellas there.
