Hi John,
I got it working! First I rendered my Sony HDR-CX7 *.mts files to MPEG-2, Blu-Ray 1920×1080-60i with file extension *.m2v. Then I rendered the audio track using *.ac3. No low memory messages at all and the rendering time was OK. I also tried .avi and that worked well too (audio included, but quality for some reason not quite as good as with .m2v and separate audio stream). After that I took it to the 5.0 version of DVD Architect to burn a BD-R disk – and it didn’t even re-compress the video stream, it just compressed a few sound files – the output is fantastic.
So I’m all good for now – thanks much for your earlier advises, Roland