Quality/compression

[sirwes]

When copying a BluRay to BD25 disc you typically see a Quality number such as 55% 41g to 23g. So does that mean that the disc will be compressed 45%? Is there a rule of thumb where it's better where to just copy the Main Movie and not the full disc such as anything under 65%? It seems like movies are intentionally crammed with extra junk to insure that discs have over 30gb knowing that BD50 media remains ridiculously priced. At the same time, some of the extras are things that I'm very interested in such as directors commentary. Is there no way to pick and choice what you want to copy on a BluRay or to split a BluRay?

thx in advance.

[mad-toilet]

The percentage you see is indicative of the size it will be compressed to from the original. In example, if it is 13%, that means the output will be 13% the size of the original, thus compressing it 87%.

Whether or not that is reasonable to you is a matter of personal preference and many people will give you many answers. For me, with DVDs, I try not go below 70% unless it is a SD tv show or something where I really don't care about the quality much. I find that I can usually not notice any artifacts, or very little, with 70% and above unless you are watching it on a 50" plus TV, and even then it generally isn't noticeable to me.

For blu-ray, right now I am backing up to DVD5 or DVD9, meaning I get percentages in the neighborhood of 13% to 45% or so (a few lower and higher too, but that is the average range for me). To be honest with you, I can tell very little difference between the original and the backup, even at 13%, with the one exception of the color seemingly ever so slightly more faded than the original. And I really mean ever so slightly - it certainly isn't enough to ruin the movie. This is not surprising considering that itunes compresses HD to 3-5GB per movie on average, and most movies going out over the air in HD are compressed as well - I definitely can't tell the difference between even the highest compression and HDTV, and when I do it is usually in favor of the blu-ray backup.

I hope that long-winded rambling helps.