[Boulder]

One other thing to try with the lossless intermediate is to forget the multithreading in Avisynth but split the encoding in multiple parts. I have a quad-core i5 so I split the video in three parts using Trim in the scripts. That is, create three scripts that handle three different parts of the video and encode in three VDub sessions simultaneously. Then join the intermediate files in the script that is fed to x264. I have found out that this is often the only way to make it work because the memory usage for HD sources is huge.