QUESTION: Just a quick followup to my other question. VOB format is basically the same as mpeg-2? Would it be bad if I recorded in mpeg-4?
Also is there a list of softwares that demux or is that kind of specialized?
ANSWER: I'm not sure what you mean by "recorded in mpeg-4". Do you mean create an mpeg-4 file for the DVD authoring software? Or the other way round?
If you /convert/ a DVD to MPEG-4, or author an MPEG-4 onto DVD then you are going through a decompression/recompression process that could affect quality. Best to demux using either MPEG Streamclip. Another one I CAN recommend is Avidemux: http://fixounet.free.fr/avidemux/
The fewer steps you go through in terms of decompressing/recompressing,the better. Demuxing is a way of extracting /without/ going through a compression stage. Demuxing keeps everything as it was, just extracts the MPEG-2 files in a way you can use them directly in Corel.
What Avidemux allows you to do is demux the MPEG information in the DVD into an AVI container, combining all the VOB files into one movie file. So if you look at the clip's properties, even though it's an AVI, the compression codec is MPEG-2. (I know this sounds like a contradiction, but this is where it's important to understand the difference between a container and a codec.) Using the 'Copy' setting in Avidemux (see image attached, on the left panel) you can demux to various containers. (NB I use Linux, so I have had varying results with Avidemux -- AVI seems to give the best result; MPEG-4 not so good, but your mileage may vary.)
A big plus is that demuxing is a lot quicker than converting from one codec to another, so a one-hour video should take a few minutes to demux. For testing what works for you, try using the A and B markers to mark off a short, say 2-minute section, to try different containers and so on... And check the audio, as I found some containers came out with no audio :(
One of the snags you may run into is the different audio tracks -- some commercial DVDs have multiple languages, or commentary tracks, so you have to figure out which to keep and which to ignore -- that's in the >Audio settings menu.
I hope I haven't confused you further... this stuff gets technical, and it can get even more technical if you start going into GOP and I-frames and so on. Also, not knowing your software puts me at a bit of a disadvantage, but I hope I have given you enough basic background for you to do some tests on your own to find out what works.
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QUESTION: Who makes avidemux and how respectable are they? I want zero risk of malware on my computer. Well handbrake exports mp4s so when I edit those I am experimenting with saving in mpeg-4 because it seems like the latest format. Must it be mpeg-2?
My concern with using VOB files directly is sometimes the audio is out of sync or the wrong language audio is included depending on where the DVD comes from which leads me to believe the IFO file must be selected to orchestrate the data. Is that correct thinking?
Avidemux is reputable open source software. No adware or anything like that. I have used it for years on Linux and Mac without a problem. MPEG Streamclip is not open source, but the company that produces it is reputable, and again I've had no problems in several years of using it. The only problem is it's no longer being developed, from what I can see.
Must it be mpeg-2? It depends what you want to do with it. The way I understand you are doing is:
DVD (native MPEG-2) --> convert to MPEG-4 (highest res/least compression possible) --> Edit --> Export MPEG-4 --> Author to DVD (which converts it back to MPEG-2.
This may be good enough for your purposes. I was suggesting keeping it MPEG-2 for the whole process, albeit using an AVI container to edit.
DVD (native MPEG-2) --> demux to AVI (keep MPEG-2 compression) --> Edit --> Export MPEG-2 at same settings or better so no compression loss taking place.
Your choice. As I suggested, try both ways and see if you can see any difference.
Notwithstanding the above, if you do want to become a Handbrake expert, take a look at this site: https://mattgadient.com/2013/06/12/a-best-settings-guide-for-handbrake-0-9-9/
It's slightly dated (2013), and Mac-oriented, but the author seems to have a good handle on how to use Handbrake to its best capability, in terms of quality. Check out the comments at the bottom -- I'm impressed that even recent queries are being answered, and several commenters have added interesting observations.