Convert DVDs with Incorrect Resolution Header?

[ProWo]

Thank you! I indeed see now that after it joins the pieces it gives the option to return to Main to do the conversion. This utility is indeed exactly what I needed!
Thank you for explaining how MP4 is like ZIP. So... Is there something like an un-ZIP utility that allows you to peek inside the MP4 and see what is inside? And to extract what is inside?

If you load your mp4 (or any other video file) in clever FFmpeg-GUI) then, after analysis, the streams contained in it are displayed.
Here you can see the individual streams (video, audio, subtitles), their codec and other information.
Then click on Main, at Extract you can extract the individual streams.

[GreenRobert]

To further clarify what @ProWo was saying,

VOB is a special superset of MPEG2-ProgramStream container format.
MP4 is MPEG4, part1 or part12/part14 container format.

MPEG basically* makes their container formats backwards compatible, so anything that was compatible in MPEG1 container ("System Stream") is compatible in MPEG2 container ("Program Stream" or "Transport Stream"). And anything compatible in MPEG 1 & 2 is compatible in MPEG4 ("MP4" container).
(*there are a few exceptions: LPCM is possible in VOBs and is theoretically possible in MP4, but I don't know of any muxers that allow it).

Also, VOBs on DVDs must, per the spec, be <= 1GB, so they are segmented. If combining, they often will have a glitch at the join point, unless one uses the information embedded in the IFO files which points exactly to the files' positions and their entry & exit points. Using the IFO, it is possible to get a seamless 1 segment clip. This clip can be exported directly to a non-DVD-compliant VOB container (as previously mentioned), pretty easily. Or if the software supports it, it can be exported to a different container (e.g. MP4). My guess is that the software in question was created back in the days of DVD, and MP4 didn't exist then, so if it hasn't been recently updated, it wouldn't support mp4. Hence the need for the interim file.

<edit>MediaInfo allows to list embedded streams in both VOBs and MP4s, as well as many other containers. Extracting is known as "Demulitiplexing" or "Demuxing". Look to the software list above for Demuxers. Personally, for DVD-sourced stuff, I almost always use DVD Decryptor, because it can do both demuxing (when needed) and joining of segments, and I have used them for both.</edit>


Scott

Thank you for that helpful information! And now am aware of another potential landmine: Glitches at the junctions of VOBs. Would this DVD Decryptor have a way to fix the aspect ratio problem that started this thread? If so, what would the settings be to take me from my DVD to the desired glitch-free MP4 with correct aspect ratio? Thanks!

[DB83]

I am not sure if you mentioned that, apart from the vobs, the ifos on the dvd were also reported to be 4:3. Now by 4:3 I mean not what you see in playback but what the aspect ratio from mediainfo (text mode - an example from your sample vob was shown earlier in this thread) is reported.

Now if all ifos AND vobs report as 4:3 then your dvr must have an output setting that forces playback to 16:9 whereas even if the vobs are reported as 4:3 but the ifos report as 16:9 if you load the dvd into any software player, including vlc it really should playback as 16:9


Now I mention this since I actually own a commercial dvd, from MGM no less so it really is not some fly-by-night operation, that has just this - all vobs report as 4:3 but the ifos report as 16:9 so playback is 16:9


And I discovered this when I sought to convert to plain mpeg2 (there should be no glitches with this method) the dvd using vob2mpg which resulted in a 4:3 mpg file and not what I expected to get.

[Skiller]

Now I mention this since I actually own a commercial dvd, from MGM no less so it really is not some fly-by-night operation, that has just this - all vobs report as 4:3 but the ifos report as 16:9 so playback is 16:9

There is a case where this is perfectly correct. Possibly that DVD has the rather seldomly used Pan & Scan display option enabled (applies only to 4:3 output). In such case, even though the video is actually anamorphic 16:9, the VOBs have to be be flagged as 4:3, and the Sequence Display Extension also has to be present and set to (most likely) a width of 540. This width then represents the indicated aspect ratio. That might seem pretty unintuitive, but it makes sense if one does the math.

[johns0]

Mp4 isn't a zip like format,it's just a different container format than vob,

[DB83]

Now I mention this since I actually own a commercial dvd, from MGM no less.....

There is a case where this is perfectly correct. Possibly that DVD has the rather seldomly used Pan & Scan display option enabled.......

Interesting. No way for me to test this and no indication on the cover. Just says AR 2.35:1 (with letter-boxing) DAR 16:9

[hello_hello]

Thank you for that helpful information! And now am aware of another potential landmine: Glitches at the junctions of VOBs

I've re-encoded truckloads of DVDs and never experienced glitches. Vob files in a sequentially numbered set are supposed to be treated as though they're one large file, which is actually what they are, only split into sections.

MKVToolNixGUI has a special mode for remuxing sets of vob files as single MKVs. Normally you'd use the "Append files" option to join files, but there's an "Add files as additional parts" option for vobs which treats them as one continuous file.
Most encoding GUI's or the tools they use treat multi-part vob files as a single file and without requiring an IFO file to tell them anything. One of the most commonly used Avisynth tools for indexing and decoding vob files doesn't even open IFO files.

You can try changing the DAR while remuxing the vobs as MKVs to see if your player will obey it, assuming it'll play MKVs, or MakeMKV is dedicated to remuxing DVDs and Blurays as MKVs. It might let you change the DAR too. I'm not sure.

If you intend to do a bit of re-encoding and don't mind a bit of a learning curve though, give MeGUI a try. If the display aspect ratio is wrong it's easy enough to change it. MeGUI uses that DAR as the starting point for calculating resizing etc. Or you can disable resizing and just re-encode using the corrected DAR. I tend to resize so there's no aspect ratio to get wrong. The video dimensions are the DAR.


[Attachment 67787 - Click to enlarge]

Cropping away the crud, de-interlacing to 60fps and resizing to non-anamorphic dimensions. With the black cropped, the remaining picture probably has a DAR of 1.8 rather than 1.778. There's also a sample of the vob file remuxed as an MKV (no encoding) with the DAR changed to 16:9 if you want to test it.

[Alwyn]

@GreenRobert, I don't know if you have sorted this out, but ProWo has modified his CleverFFMPEG GUI to add a feature which will change the aspect ratio of your VOB from 4:3 to 16:9.

It works well.

[jack616]

FWIW
Aspect ratio is controlled in 2 places:
The encoded pixel aspect ratio (PAR) and the Display aspect ratio (DAR)
the ffmpeg docs have an explanation.
I spotted this when UK freeview broadcast entire series in the wrong ratio
and had to add the 2 means of correction into my own ffmpeg toolkit.