This is more just a curiosity question, nothing practical or problem solving. It relates to set-top DVD recorders.
We are on our second DVD recorder and while they could never do what I can with a PC solution, set-tops are very convenient for recording off-air or converting pre-DVD home videos.
Many limitations of set-tops are trivial and/or easy to understand why the limitations exist, but there is one limitation that baffles me.
It relates to maximum recoding time on a DVD. Documentation for DVD recorders indicate identical resolutions in different modes (i.e 1 hour and 2 hour modes are both 720x480 or something similar. So I have to assume the difference is the level of compression of each 720x480 frame OR the frame rate. Three hour mode cuts the horizontal resolution more than 50%.
My experience is that there are a LOT of movies in the 2 hour 5 minute to 2 hour 15 minute range. I can't stand to watch a movie recorded in three hour mode.
Our DVD recorder actually will record an extra 3 or 4 minutes in 2 hour mode. I understand that a 2.5 hour movie would be degraded more than I (and many) would accept if squeezed onto a single layer DVD. But I doubt I would be able to see the difference from compressing just enough to get another 5 to 10 minutes on.
Like I said, there are a LOT of movies that are just barely longer than will fit on a DVD in 2 hour mode. Our Dish DVR has over a dozen in it from the last week alone. Its a huge increase in effort to copy each onto 2 DVD+RWs in 2 hour mode with overlap and then edit those on a PC and reburn them on to 2 DVD+Rs with a logical break point. At least some burning software lets you do that without recompressing the video and hurting the quality. But its still about 50 times as much work and less convenient to end up with 2 DVDs (each barely half full) for those movies.
I know that dual layer DVDs are an option but the media cost is still astronomical and there are much fewer dual layer set-top burners to chose from. Not to mention the glitches I read sometimes happen when the layers switch.
So given the high % of movies in the just barely over 2 hour length and that PC software can easily compress to an exact fit to the media so the quality is as good as possible, why aren't there lots of DVD recorders that will let you specify the run time and compress just enough to fit it on a DVD?
Sure there is the extra interface and logic to let the user specify the record time. but that seems trivial. And the compression code might be more complex BUT the algorithyms already exist and the current code either could already handle variiable compression rates OR they have space consumin separate code for each fixed length (1 hour, 2 hour, 3 hour, etc.)
I don't understand why more brands don't grab a big competitive advantage by offering this capability.
Even the customers who currently use 3 hour mode to record anything between 2 and 3 hours would surely appreciate the increased picture quality offered by using the entire DVD to cut back on the quality robbing compression needed.