Why can't DVD recorders optimize compression for the media?




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.


It’s called…“Let’s not get the motion picture companies angry at us, especially if we make motion pictures too.” These companies didn’t worry all that much about recording to VHS because the quality was so crappy. But dvd is a whole other ball game.
See, HoosierDaddy (nice avatar, BTW), If you look closely at any PVR or Dvd stand-alone recorder you will notice one thing. They don’t have component, HDMI or DVI INPUTS, but heaps of quality video OUTPUTS. Why not inputs…easy answer; that would mean that any Joe Bloggs could produce a high definition copy of a live-to-air program, given that they have a digital STB.
For at least two years I have been pestering my local electronics retailer here in Australia to find out just when a Dvd stand-alone player/burner with a built-in digital HD receiver would be released only to be told, on the quiet, that it would probably never happen, due to “copyright concerns”.
So I went out and bought the best PVR I could find (if you’re in the States, this is like your TIVO unit), a Toshiba HDD-J35 with a high definition receiver, a 160 Gb HD and HDMI/component “out”. Like you, I was hoping to archive to DVD by connecting a DVD stand-alone player/burner but was still constrained by the disk recording capacity and the lack of component/HDMI inputs. I have been told by a techie friend that it is technically feasible to dabble in the electronics of the burner to up the compression rate and it would be possible to dabble with the main board of the burner to obtain hdmi/component inputs…but only at huge cost and huge risk of electronic (and costly) malfunction. End result…I don’t archive at all…aint worth it.
The only light at the end of the tunnel is the Chinese who will no doubt fill this void in the market with some sort of device in the near future because they don’t give a damn about offending any motion picture company.


That explains a lot!

What a shame just like all the downsides to DRM.

Off topic: functionally, I would have prefered a Sony DVD recorder over the Liteon I bought but Sony’s documentation had more footnotes, sidenotes and in-line notes about copy protection than usefull consumer information PLUS Sony had infected over a half million PCs with their rootkit crap on audio CDs. So I (like many others) am boycotting anything from Sony for a LONG time.


You might find these articles interesting…read here why I’m happy to live in Australia:



There are a few DVD recorders out there, that with hacked firmware, are capable of recording 3 and 4 hours to DVD5 (4.7gb).
One I know of is LiteOn with their 5xxx series. If you check at www.videohelp.com and look at the dvd recorders, you should find a few others. You should also be able to do a forum search and see what folks have to say about the quality of the 3 to 4 hour recordings.


My parents, who seem to have more (borrowed) dollars than (technical) sense, bought a Pioneer DVD-only recorder some time ago. (It cost them near-on $2000, I think.) It’s a nice-looking machine, but the only thing that it has going for it w.r.t. my recently-purchased $349 MTV TS-2080 DVD[I]+HDD [/I] recorder is the ability to select one of 32 compression levels.

My MTV recorder has an “SP+” option, which will fit around 2½ hours on a SL disc; sounds like that’s what you need.


Yeah, a 2.5 hour mode might do it IF it stays with 720x480 resolution. I’m sure the drop to 3xx horizontal in 3 hour mode is what makes 3 hour mode so bad.

I can’t find a link to a MTV DVD recorder; anyone have one? The music chanel with the same initials clogs up any web search.


Sorry, I used that as an example, because I have one. But the way you’ve been talking “720x480” suggests that you’re probably in the USA. As you can see on the left, I’m in Australia (720x576, PAL, etc).