This may seem to be a difficult question to generalize on, but I was wondering if there is a general "Maximum" compression one would consider when backing up DVD Movies? Like, is 75% the most you should go for in a compression, with out sacrifice video and audio quality. ??
I know this is not an exact science, but a ball park figure would be good to keep in mind.
i presume you are using DVD Shrink. different programs do the compression differently. people say that somewhere around 70%, they do not see a difference with compression. in those situations, they use the deep analysis which will add 40 minutes to the whole ripping/compressing process.
again it depends on the program, setup, video monitor, etc and you will have to play to find your limitations.
That is correct, I should have mentioned that I was referring to DVD Shrink.
I have played with a few backups at different compressions. The most being 76% and I saw no loss of video quality or sound, but I thought there may be a "sliding" limit of like 70% before you begin to truly see decreases in audio or video quality.
I've used compression ratios up to 60% of the original movie with good results, but this depends heavily on the movie. On some action movies, where the screen changes constantly, only little compression can be used without sacrificing the quality, but some dramas for example, where the background remains constant for longer times and the screen moves only slowly, quite heavy compression can be used without any noticeable effect.
I always check the quality of the compressed movie before burning - for this I use my 18" TFT screen, which reveals bad image quality much easier than a TV, even a big TV.
Extreme close-ups of faces and smoke/fog/clouds or the like reveal the problems the easiest if too much compression is used - the edges will appear "squared" and you'll start noticing little boxes, and the different colour shades will have sharp lines between them.
Sometimes using the beta version of DVD Shrink even small compression ratios (like 80% or so of original)have caused unacceptably poor quality, I don't know why, so on those occasions I've used DVD2One instead with a better result.
But I guess there is no way of determining an absolute maximum value of acceptable compression, it all depends on the movie and on your own judgement about what is "good" quality and what not.
