Best settings for quality/size trade-off when exporting to QT?

Question

Hi All,
I've been using Keynote '09 (5.3) to record narrated slide shows (slides with me narrating by voice) for my online class "lecture" podcast series for a while - now that the beloved, but quirky and unsupported, ProfCast has fallen by the wayside. This works well - as we all know - producing clear audio and visuals that upload well to YouTube, where I am now hosting the files.
The problem I'm running into now is that my lectures often last around 50 minutes, and this produces enormous file sizes (like the original Keynote file comes in around 800MB with the slideshow saved). I've been exporting to Quicktime with full size video and mixed audio set to AAC, and this produces a QT mov of around 130MB or so. Still quite large, but at least manageable for uploading, even with DSL at home.
Ideally, though, I'd have even smaller mov files, but without much loss in quality. In my earlier experimentation, I realized that it was the audio that was eating up loads of space. However, switching to half size video cuts the same file to around 80MB as well. Once I've opened the can of worms of custom audio and video settings, I feel like there are many, many possible combinations of sizes and qualities...and it's difficult to steadily compare each and every permuationg (it takes a while for each export to run!).
So, the question I have is: are any of the other AAC settings in the menu likely to make a significant dent in mov file size? Or, are these really just small differences on the margin? Even if I stay with AAC overall, would tweaking the kHz Rate make much of a difference?
Looking forward to any wisdom from experience you all might have to pass along!

Answer 1

I was looking for command-line PDF conversion tools and eventually found out this:
https://www.pdf-tools.com/pdf/pdf-optimization-reduce-size-1.aspx
To me, it is way too pricey (US$ 570), but maybe it's a viable solution to you. It has  watched folder workflows, therefore it can be handy for your purposes. You can download a demo and even test it online (the resulting PDF is watermarked).
I submitted a file to their online testing page and were impressed with the results: a 1.5 Mb original PDF resulted in a 925 Kb file (while an Acrobat "optimized" file ot the same sample PDF turned out to be _bigger_ then the original). What makes it even more impressive: in the online test I deselected ALL the image downsampling settings, to force the optimized PDF to keep the original image quality and resolution. Then, in Acrobat, I exported the images from both the original PDF and the optimized one, and compare them in Photoshop. They were not identical, but the difference is pratically imperceptible. I guess that applying downsampling to the test will result in even smaller PDFs, but I didn't test this.
Anyway... I don't have any affiliation with those guys, and I don't have either the need nor the money to buy this product. I'm only sharing these thoughts because they may point you to other ways to find a solution. The above mentioned application seems to be very efficient. If you can afford it, then I think it deserves a try. If not, you can search the Web for plugins or other tools that can fit you needs and budget. Acrobat/InDesign approaches are not the only way to go.