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Well, it clear no-one knows the logic behind it, saying it's variable compression makes no sense as the algorithm doesn't know the disc size, or why the size is inconsistent with high and standard quality.

The compression is deterministic, not some random values that pulled out of thin air each time.
So the bottom line is that you are saying power2go is just rubbish at predicting file size and they can't control the bit rate.

i am very familiar with video compression, and have ripped, or transcoded many video files for my kids to watch stuff on iPad or phone. Mainly using ffmpeg, and that does a very good job of getting the average bit rate close from the start of the conversion.

But here's the thing, although the bit rate is variable, the algorithm is fixed. So when I compress or convert the video format from one to another, then if I do it again with the same command line setting for encoding, bit rate, video size, etc, then the output file is the same size! It won't change based on the medium it is destined for.

Maybe power2go is just too basic and lacks the detailed control I like. To randomly change the bit rate based on medium makes absolutely no sense.
I get it's a variable bit rate, and the actual size is a guess.

What doesn't make sense is the random change in quality that's not reflected in the settings. And if I choose 'high' then the dual layer size jumps to 4Gb, so it's clearly not maximising the bit rate at 2.3Gb.

where does it show the actual bit rate?
If I'm happy with the quality at 1.7Gb, where can you set the same quality for the dual layer setting?

Again, where's the logic in changing the bit rate behind the scenes between single layer and dual layer?
So what's the point of the quality setting?

There is 'high', 'SP' and 'LP', with the bit rate beside it, and if I change the bit rate too 'high', then the size on disc changes accordingly. Changing to 'high' sets it at 9.5Mb/s and almost doubles the size on disc.

And if there is only one video of 1-hour on a single layer 4.7Gb disc, why would it not also increase the bit rate, since there's lots of free space unused?
When burning 2 videos to a single layer disc, then it uses 3.2 - 3.4Gb, leaving wasted space. It seems a flawed logic here.
Sorry for the delay, options selected here, and 1hour dvd file added to project:

Flicking between 4.7 and 8.5Gb discs will change the size to 1.7Gb or 2.3Gb respectively.
I had a number of video files that I was burning to standard dvd.

I have a number of singles and dual layer discs. The files are encoded to DVD mpeg2 format, so should import with no issue,
and they do, only the size used for a dual layer disc is much larger than single layer.

A 1 hour movie clip is 1.6GB on single layer disc, and 2.2Gb when put on dual layer. Both have the same quality settings. I was hoping to get 5 videos on the dual layer as I can only fit 2 on a single layer (just short of the 4.7Gb limit).

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