Hi, this question concerns using recode to copy DVD9 titles > DVD5 and is a bit long, but you can skip to the bottom first if you think you understand my question right away.
I've been experimenting with different disks and titles but as yet still can't figure out exactly what the relationship is between the horizontal position of the pip on the slider and the numerical expression of "Video Quality" in a percentage figure.
It seems obvious that the far right of the slider represents the highest quality video (i.e. original quality) or in other words, no compression. 100% is the constant figure there, so no mystery.
I gather the far left of the slider represents the lowest quality Recode will encode to, or rather, the highest level of compression possible for any given video file. I see as the slider moves left, the numerical expression of video quality descends; I think it is also obvious that the level of compression of the selected title increases.
What I don't understand is why, when I move the slider pip all the way to the left for a given title, the video quality percentage expressed can be anywhere for 60% to maybe 20%. Or why when I move the slider pips of two titles all the way to the left, one's "video quality percentage figure" may stop at 36% when another stops at 45% (even though both pips did move all the way to the left and are aligned vertically.
I thought that it was possible the compression rate of the original mpeg-2 may have some bearing on this, yet when I tried to compare titles of the same aspect ratio with the same compression rate (as shown on the info tab when encoding to mp4), I still found discrepancies in how Nero related "Video Quality".
I checked to see if maybe one title was progressive and another was interlaced, but even that led to no solution. All things being equal, nero's represented video percentages weren't. I even tried eliminating all audio tracks so that they could not factor into the equation; since I believe that nero does NOT re-compress audio when going from DVD9>DVD5 (Correct?).
You see, I'm trying to understand how the software works so I can make the best decisions for my specific recoding needs.
I'm confused by the fact that when I want two titles to have the same level of compression, based on a ratio of original file size and output file size (or the opposite - when I want two titles to have the output same apparent video quality after the recode is complete) ...
... do I line up the slider pips vertically on the screen; so each pip is at the same point between the left extreme and right extreme as all other pips?
... or do I adjust the sliders so that each title indicates the same "video quality" percentage number even though this usually means the relavent slider pips are all over the place?
Here's another thing I tried, to prove what the percentage figure was:
A given title (NTSC 720x480 Mpeg-2 16:9 Progressive 1 Hour 41 Min 31 Sec) at 100% (With target set to DVD9 ALL titles indicate 100%) with audio and subtitles removed shows a file size of 4,169 MB. I uncheck "fit to target" and slide the quality slider to the far left and it stops at 39.9%. Why does it stop there? Why not 45% or 20%? What does this mean?
Anyway, file size show at 39.9% is now 1677 MB. This is close to 40% of the original file size so does this mean the percentage number only refers to the ratio of original file size to output file size?
I next move the slider till I see "50.0%". File size is now 2096 MB. 50.0% of the original file size is 2184 MB; so I'm a bit off here but not much. At 80.0% I show a file size of 3342 MB, so I'm really starting to buy that "video quality" just represents how much compression is to be applied. I notice adding and removing audio tracks does not seem to effect either pip position on the slider or the percentage figure.
Anyway, Since Nero Recode defaults to putting all the pips in a vertical line instead of setting each title to a specific level of compression based on file size percentage - WHAT DOES IT MEAN WHEN THE PIPS LINE UP VERTICALLY? And why does Recode do that by default when it needs to compress a DVD9>DVD5?
Any help understanding this fine software would be greatly appreciated.