I used to grab/convert my video from my cam in mpeg2 format at 8000 KBs (previously in Ulead on windows and now in Kdenlive on Feisty) and not in DV. This enables me to use smaller files, use the quality that is getting on DVD and speeds up the render process enormously (It's already in MPEG2 and only addtional transitions/clips and so on need to be rendered). However, in Kdenlive now I would like to convert the massive DV files to mp4 files. When I convert them to mp4 I use 5000 KB/s which gives me perfect quality and even smaller files than MPEG2. However, when creating a "standard" DVD I want/need the bitrate for the MPEG2 back to 6000-8000 KB/s. I think this should work based on the assumption that 5000 KB/s mp4 contains much more "video information" than 6000-8000 MPEG2. Therefor, when uncompressing the 5000 KB/s mp4 stream and recompressing it to 6000-8000 KBs MPEG2, the uncompressed video stream/information should even be "down sampled" in information, therefor not losing any quality.
Is this assumption correct and does that work?