This is not so much a question about how to do this, as about the file I actually have and whether converting to a DVD will inevitably lead to a slight deterioration in quality.

I should stress I am no expert in stuff like this, but I understand a little bit of the theory.

So, I have been given a reasonably large mp4 file 2.8G). I managed to convert it to a DVD by both DVD Styler and Kdenlive. DVD styler gave me about 2.1G of video files, Kdenlive much smaller at about 1G. However, in both cases you could definitely see a deterioration in quality. So, I did a bit more digging and I am wondering whether I have actually been given a hi-def file and a conversion to DVD will inevitably lead to an inferior quality file?

So, Kdenlive says the original file has the following properties:

Image Size: 1280 x 720
Frame Rate: 29.971

Some very basic understanding of video suggests that this is what you'd call on a high-def TV 720 resolution. So, not 1080p, which I believe is best HD resolution, but 720 (p or i, I don't know) which what a lot of early HD TVs were capable of.

I think DVD is maximum resolution of 720x576 for PAL (I'm in the UK, so that's what we use), which is clearly less than the original file.

Is my thinking correct, and am I urinating in the wind attempting to get the same quality on a DVD as the original file? Would I really see that degreidation on a computer screen? I guess there is a good chance as it's a 1920 x 1080 screen and I'm going down to a much lower resolution.

Many thanks

Going from 1280x720 to 720x576 is of course a drop in resolution. But does it matter? How big is your TV screen (physical size, not maximum resolution)? How far do you sit back from your TV screen when viewing? For example, I have a 70" screen and we sit 14 feet back from it on our couch. At this distance, the human eye cannot tell the difference between 720 and 1080. Your eyes have limits on what they can resolve too.

Point being, before you get too worried about a "loss in quality", make sure that it would apply to your specific circumstances. I'll attach a chart showing this (sorry, you'll have to do your own conversions from feet to meters and inches to centimeters since you use a different system than I do in the U.S.)

Furthermore, are you watching videos for content, or resolution? I admit, that when I first pop in a high-resolution source to view on my TV (remember, my eyes can only resolve up to 720 from my viewing distance), I say "Wow! This is impressive!" But after 2.46 seconds of drooling over the picture, I revert back to just watching the content, and for that, I'm just as happy watching at 480 lines of resolution (the standard for a U.S. NTSC DVD).

A bad movie is still bad, even in HD. A good movie is still good, even at lower resolutions.

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I fully take and accept all your points...

...but (you knew it was coming! ), I was asked to do this for someone who has put a lot of time and effort in to creating a video to promote her little business, I just didn't want to send back something that I can see is lower quality. Unless, of course, as seems likely there's little I can do about it.

My TV is 50", and I would most definitely see the difference on that, but I don't think that's really the issue. Your point about what other people will watch on is fair and I wouldn't be surprised if most people couldn't even see the difference. However, I'm just trying to make sure I do the best I can for my friend. You can really see it on things like skin; there's a definite degridation in quality, but it may well be if that the original file was in DVD resolution in the first place it would have looked the same!

I must confess, when I watch films on Blu Ray vs DVD on my big screen the difference is minimal for most films, so I was a little surprised that the difference was noticeable here. I will hook up my laptop to the TV and see how much of a difference I can see there!

Thanks for the post!

Depending on HOW you convert things, this can make more of a difference in quality that moving from HD to SD.

Bottom line: If you're creating a DVD, you are stuck with DVD resolution. No way around that.

I would look at what conversion parameters you are using and see if quality can be increased there. There are typically a ton of parameters, who's exact use is known only to the software's developers and a few hard-core video transcoder users. I tried learning this once or twice, but found it wasn't worth my effort. I have since started using a handy little program that has pretty decent preset (default) conversion settings (I've only used it a handful of times, but when I've used it, it's been good). My use was just like yours - convert MP4's to DVDs.

Check out "WinFF" http://winff.org/html_new/index.html It's probably available in your Linux distro's repos.

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Because the MP4 & DVD codecs are different, you will always get a video conversion and a consequent (slight) loss of quality.
Unless you start with a very hi-res MP4, this will always be noticeable.

For Linux, try DeVeDe - it's very simple to use.

BTW HD (UK) is 1920 x 1080.