Understanding DVD & Ripping Resolutions

[nxmehta]

I'm trying to figure out what resolution to backup my DVDs in. Tried to do a search but couldn't find anything that would explain this clearly. I'd also like to verify my current understanding of DVD resolutions. However, if you feel that my questions are answered elsewhere please feel free to point me to the correct thread(s).

My goal is to make DVD backups to the hard drive that are as close in quality to the original DVD but smaller than 4.7GB. I want to encode in H.264 since I figure that will give me the highest quality for the smallest file size. I don't have a target filesize; I want the file to be noticeably smaller than a DVD but as close to indistinguishable in quality as possible. My first assumption was that I should rip and encode my DVD at the same resolution that it is originally encoded in (we can question this assumption later). So I set out to understand how DVD resolutions work.

My first question is to verify that I understand DVD resolutions correctly. As far as I understand it, DVDs are encoded in 720x480 resolution. This is some weird 1.5:1 format (why they decided this, I have no idea), so to get 1.78:1 video (widescreen tv aspect ratio) they encode the video anamorphically. If the DVD does not appear letterboxed on my widescreen TV, then I can assume that the resolution of the original is 853x480 (480*1.78=853), correct? If the movie appears letterboxed on my widescreen TV, this means that it is not natively formatted in 1.78:1 (which typically it's not?), but rather in 1.85:1 or 2.39:1 (or is that 2.35:1?) and when anamorphically encoding they also had to add letterboxes to the DVD. Then, the resolution of the original is something like 888x480 or 1148:480, correct? Or, still 853x480 if you include the letterboxes? If you want to strip those letterboxes... I'm not sure how to figure out what the original resolution is then.

My next question is to understand how to choose a resolution for DVD ripping. Many guides I read about ripping talk about encoding at all these weird resolutions (512x272, 512x384, 640x272, etc) which target the correct aspect ratio of the source material, but are not the same resolution. Why would somebody do that? Wouldn't it require your computer/player to rescale the image to watch in on a TV (resulting in a quality loss)? Or is it just to reduce the size of the file.... It seems to me though that this would significantly reduce the quality of the movie (particularly if you had to restore your DVD backup by burning it)? I know that bitrate is also an important value to select when ripping a DVD, but isn't retaining the original resolution the most important? If I don't have a target filesize, then do I have any reason to rip at a lower resolution?

Thanks for any help.

[setarip_old]

Hi!My goal is to make DVD backups to the hard drive that are as close in quality to the original DVD but smaller than 4.7GB.If this means that you intend to retain the DVD format (.IFOs, .BUPs, .VOBs), the simplest approach would be to load the DVD into DVD Shrink and set it for the total combined filesize you desire...

By the way, the actual single layer DVD capacity, using computer definitions, is actually 4.37Gigabytes

[nxmehta]

I want to encode with H.264 (I'll update the original post). Thanks for you reply though!

[neuron2]

You're not making much sense. You say you don't have a target filesize and then you say you want it noticably smaller than the DVD size. Why? What are you trying to accomplish?

Your post is of a "kitchen-sink" nature. A lot of people will react this way: "So many questions, so little time." :)

[nxmehta]

You're not making much sense. You say you don't have a target filesize and then you say you want it noticably smaller than the DVD size. Why? What are you trying to accomplish?

Your post is of a "kitchen-sink" nature. A lot of people will react this way: "So many questions, so little time." :)

Well, I want it to be smaller than a DVD because I can't backup my DVD collection with the hard drive space that I have now. Even if I buy another drive or two then I wouldn't be able to fit it all if I backed up @4.7GB a movie. 1-2GB a movie, maybe, depending on how much $$ I want to spend. Do I care if it's 350MB/700MB/1.5GB/etc a movie? No. I just want it to be comparable quality to the DVD and in the ballpark of under 1-2GB. Is that a situation that doesn't make sense?

I had several other questions in the post that I thought both made sense and that people here could answer. Maybe we can just stick to these questions instead of what my specific goal is. Here, let me list them to make it clearer:

1. Is my understanding about DVD resolutions correct (trying to figure out what the source resolution of the movie is)?
2. Is it generally a good idea to rip the DVD at it's source resolution?
3. Is the only reason that people choose lower resolutions to save space?
4. What are the effects of encoding in lower resolutions in terms of quality (seems like requiring your playback mechanism to resize the video would introduce errors)?
5. How does lowering resolution compare to lowering bitrate instead (my intuition is that it's more important to keep the original resolution, but people don't do that, so...)?

[Sith Lord]

Well, I want it to be smaller than a DVD because I can't backup my DVD collection with the hard drive space that I have now. Even if I buy another drive or two then I wouldn't be able to fit it all if I backed up @4.7GB a movie. 1-2GB a movie, maybe, depending on how much $$ I want to spend. Do I care if it's 350MB/700MB/1.5GB/etc a movie? No. I just want it to be comparable quality to the DVD and in the ballpark of under 1-2GB. Is that a situation that doesn't make sense?

Do you want to save all your DVDs to hard disk or do you need just enough space to burn a backup? It's a little confusing. Why not just back up one movie at a time and delete those files you already burned to DVD? If you just need space to copy one DVD at a time maybe you could temporarily move some files to a different partition or disc to free more space, for just as long as you are burning movies, then move them back to the original position. If you want to back up movies to DVDs I suggest you try DVD Shrink. It lets you choose which contents of the original disc to copy. To save space, you can leave out audio tracks, subtitles, menus or extras you don't need, and only copy those parts you'd like to keep. I copied a few DVD-9s to DVD-5, and some of them are not bad quality wise. Of course it probably depends on the size of the original disc. But it's worth trying so you can check the result yourself. Some of the copies I made are really close to the original quality. But if you can, why not burn to DL discs instead, without any compression?

[setarip_old]

Cost seems to be one of the factors that you wish to take into account.

In light of the fact that high quality burnable DVD media can be purchased for approximately 25 cents U.S., or approximately 17Gigabytes per $1 U.S., you might want to consider simply burning DVD copies...

(If you lose or damage a DVD, you can always make another backup copy. If you lose your harddrive, you will have lost ALL of your DVD copies)

[nxmehta]

Hmmm, this thread is not going in the direction I planned. I want to put my DVDs on HD. I understand the dangers/cost in doing this. That is not something I am trying to decide on. Lemme repost what my questions were.



Maybe we can just stick to these questions instead of what my specific goal is. Here, let me list them to make it clearer:

1. Is my understanding about DVD resolutions correct (trying to figure out what the source resolution of the movie is)?
2. Is it generally a good idea to rip the DVD at it's source resolution?
3. Is the only reason that people choose lower resolutions to save space?
4. What are the effects of encoding in lower resolutions in terms of quality (seems like requiring your playback mechanism to resize the video would introduce errors)?
5. How does lowering resolution compare to lowering bitrate instead (my intuition is that it's more important to keep the original resolution, but people don't do that, so...)?

[smok3]

1. yes, at least for ntsc releases.
2. sure, but you need to plan ahead and see what players you will use, and if those players can handle anamorfic playback correctly (test your entire playback chain on a small sample)
3. + to make a movie pixels 1:1.
4. sorry?
5. complex question it is :)

[neuron2]

4. Yes, quality is obviously affected. It's a stretch to call that an error, though.

My 2 cents. You say ~4GB per movie is too much, but ~2GB is OK. That just means you need twice as much disk space. It will save a good deal of aggravation and a LOT of time, especially given that you say you have so many DVDs, if you simply get some more disk space compared to re-encoding everything to AVC. I bought a 750GB drive for less than $200. The time it would take me to convert so many DVDs would translate to many, many times that. You'll be able to just rip to ISO and play them on any software player. AVC playback is touchy. Finally, if it is an external USB drive, you'll be able to move it easily from PC to PC.

[foxyshadis]

Cost seems to be one of the factors that you wish to take into account.

In light of the fact that high quality burnable DVD media can be purchased for approximately 25 cents U.S., or approximately 17Gigabytes per $1 U.S., you might want to consider simply burning DVD copies...

(If you lose or damage a DVD, you can always make another backup copy. If you lose your harddrive, you will have lost ALL of your DVD copies)

On the other hand, you're much more likely to lose/damage a DVD, plus the effort and time that goes into archiving makes it a false economy for people like me. I already went through a period with over a hundred CDs in binders and spindles once, never will again.

nxmehta, even if you have a lot of 7-8G discs, it'd still probably be worth buying another drive instead of spending all the hours converting, if only because all of that effort will be wasted as soon as you buy next year's $100 terabyte drive and want to re-rip everything to get the menus and maximum quality back. If you still want to, you can download MeGUI or another gui (see the forum for them), pick a profile speed and set it to constant quality 18 (large but much smaller than DVD). Alternately and even simpler & faster, Handbrake at 90-something% quality.

[nxmehta]

3. + to make a movie pixels 1:1.
5. complex question it is :)

For #3, can you explain what you mean?

For #5, are there any hints or intuition that people can give on how one selects a bitrate/resolution for ripping? Or do people just make arbitrary decisions? I'll take a pointer to an article if it's too complex to explain.

[nxmehta]

On the other hand, you're much more likely to lose/damage a DVD, plus the effort and time that goes into archiving makes it a false economy for people like me. I already went through a period with over a hundred CDs in binders and spindles once, never will again.

nxmehta, even if you have a lot of 7-8G discs, it'd still probably be worth buying another drive instead of spending all the hours converting, if only because all of that effort will be wasted as soon as you buy next year's $100 terabyte drive and want to re-rip everything to get the menus and maximum quality back. If you still want to, you can download MeGUI or another gui (see the forum for them), pick a profile speed and set it to constant quality 18 (large but much smaller than DVD). Alternately and even simpler & faster, Handbrake at 90-something% quality.

Thanks for your reply. Ok, couple of questions then. First, what's the simplest way to make a 1:1 copy of a DVD, ready for hard drive playback? I guess I could use Alcohol with AnyDVD to remove the protection, and create an iso or mdf?

Second, about ripping at constant quality... I have MeGUI and all the profiles and I was reading the thread about what they are for. For constant quality I want the CQ profiles. There are two lossy profiles, but I can't figure out the difference between them. Also, what would be the expected filesize reduction when using CQ?

Finally, if I understand the idea of CQ correctly, it tries to make each frame of contant quality, and figures out whatever bitrate it needs to do that. If I take the avg bitrate of what CQ produces and do a 2-pass encode with that as the target, will that give me equivalent quality with an even smaller filesize? Don't everyone freak out about me actually doing this- I'm just trying to make sure I understand things correctly :)

[smok3]

3. its just easier to handle files that have PAR 1:1
http://en.wikipedia.org/wiki/Pixel_aspect_ratio
5. decisions people make are different and they are usually connected to the source quality, but you may find some really crazy threads around here on how to calculate compressibility.

[neuron2]

First, what's the simplest way to make a 1:1 copy of a DVD, ready for hard drive playback? I just use DVD Decrypter in ISO mode and then open the ISO with VLC.

[foxyshadis]

Thanks for your reply. Ok, couple of questions then. First, what's the simplest way to make a 1:1 copy of a DVD, ready for hard drive playback? I guess I could use Alcohol with AnyDVD to remove the protection, and create an iso or mdf?
I do the same as neuron2, though sometimes you have to use ripit4me or dvdfab decryptor, and I use daemon tools to open them. Same diff.

Second, about ripping at constant quality... I have MeGUI and all the profiles and I was reading the thread about what they are for. For constant quality I want the CQ profiles. There are two lossy profiles, but I can't figure out the difference between them. Also, what would be the expected filesize reduction when using CQ?
All of the profiles allow constant quality, that CQ profiles are just conveniences. The only change you have to make it to press config, change the first dropdown from two-pass to constant quality, choose a crf (18-24 is the common useful range, lower is better/larger, one or two tests should tell you what you like), and save.

Finally, if I understand the idea of CQ correctly, it tries to make each frame of contant quality, and figures out whatever bitrate it needs to do that. If I take the avg bitrate of what CQ produces and do a 2-pass encode with that as the target, will that give me equivalent quality with an even smaller filesize? Don't everyone freak out about me actually doing this- I'm just trying to make sure I understand things correctly :)

No, average bitrate is just size/time, no matter how you arrive there the same bitrate is the same size. There are some differences in crf versus 2-pass, but they're much smaller than in most codecs, and shouldn't be visible in the end result unless you use extremely low bitrate. Unlike const. quantizer, crf is more like a 2-pass with no bitrate target.