We received specs from the company that's doing our sound mix. They'd like a DVCProHD, 960x540 Quicktime. Our workflow for such turnover is: output from the Avid that is captured into FCP (specs below) and use Compressor to create different compressions/watermarks for distribution to our vendors. I created a Compressor setting matching the company's specs, but Compressor always gives me a DVCProHD 1280x1080 (though in the normal and actual size lines of the info it says 1920x1080). I assume this is possible, as these are their specs they give to everyone, but I don't know how to make it work.
It's really odd; DVCProHD is really meant for 1280x1080 and only that.
My guess is that compressor is sensing DVCProHD and ignoring any setting. I just tried it in QuickTime directly and it did what you said. I'd ask them what software they're using to make 960x540 DVCProHD files.
I haven't got the time today to check this in Episode or Squeeze (but you may have a copy of squeeze that came with your avid.)