Odd Frame rate readings in Mediainfo from NTSC mkv files

[mattias83]

I have a number of small shorts that long ago I extracted using DVD Shrink, creating a separate DVD folder for each short.

I'm using MakeMKV to remux them into mkv files. But the extracted mkv files are giving me odd frame rates.

If I view the frame rate of the DVD folders in mediainfo it reports NTSC/29.970.

If I view the frame rate of the remuxed mkv files in mediainfo or MPC-BE, it reports odd frame rates. Here are some examples:

Frame rate mode: Variable
Frame rate: 25.996 FPS
Original frame rate: 29.970 (30000/1001) FPS

Frame rate mode: Variable
Frame rate: 24.062 FPS
Original frame rate: 29.970 (30000/1001) FPS

Frame rate mode: Variable
Frame rate: 24.044 FPS
Original frame rate: 29.970 (30000/1001) FPS

Frame rate mode: Variable
Frame rate: 24.229 FPS
Original frame rate: 29.970 (30000/1001) FPS

Frame rate mode: Variable
Frame rate: 24.081 FPS
Original frame rate: 29.970 (30000/1001) FPS

And interestingly if I use an alternate program to remux them (total video converter, which has a lossless copy function), I get even weirder frame rates in mediainfo:

Frame rate: 550.079 FPS
Frame rate: 535.216 FPS
Frame rate: 651.353 FPS
Frame rate: 185.139 FPS

* Oddly, If I view these same mkv files in VLC (tools>codec information), it reports 29.970030 for all of these. SmPlayer and the old MPC-HC also report 29.970. Only mediainfo and MPC-BE report these wacky frame rates.

Could it just be something odd with mediainfo and MPC-BE reporting those frame rates, and the files are actually fine?

[Woodstock]

The wildcard in this is DVDShrink - what did it do, when extracting the data?

One thing it was supposed to do is re-encode the video so it was small enough to fit on a single-layer DVD. It has to maintain MPEG2 encoding for compatibility, but there are a LOT of things that can be done. I've seen disks that will still play in a DVD player, but combine 3 DVDs into 1.

[mattias83]

I didn't use DVD shrink to re-encode. I use "no compression" to simply copy/remux the files to their own separate DVD folder. I never re-encode with DVD Shrink. And those new DVD folders processed through DVD Shrink test as NTSC/29.970 in mediainfo. If I drop the VOB files in mediainfo, they say NTSC/29.970. But then the mkv files remuxed straight from those folders give me these wacky numbers in mediainfo.

Thinking again, those higher numbers from total video converter remuxes are from mkvs taken straight from makemkv. No DVD Shrink used anywhere in-between. For those mkvs (550.079 FPS, etc.), I had makemkv remux to mkv straight from disc because total video converter (and makemkv) can't split/demux by chapter from DVDs. But total video converter can do that from an mkv, if it has chapters. So I have makemkv remux the disc to an mkv, which retains the DVD's chapters, then I use total video converter to split the mkv by chapter and then remux to separate mkv files by chapter. That's great for splitting a DVD full of shorts that are encoded as a single, long feature, only separated by chapters. So disc>makemkv>total video converter. Remuxing all the way.

The ones with the lower framerates (24.062 FPS) are the ones where I have makemkv remux smaller DVD folders that have been remuxed/processed by DVD Shrink.

So I'm still wondering if it's mediainfo that's giving false information. Remember, mediainfo and MPC-BE are the only programs that are giving me these wild frame rate readings. All other media players report 29.970. And the files play fine on all my external media players. But I was hoping to verify if it is indeed a known glitch with mediainfo reading NTSC files, or if there's actually something wrong with the files I'm outputting.

[Woodstock]

It would not be the first time Mediainfo reporting things "almost correctly". How recent is your copy? Supposedly there has been a lot of work toward getting Mediainfo to make fewer wild-ass guesses when the metadata isn't "perfect".

[mattias83]

I'm using the latest version of mediainfo - 20.09 GUI. I had a somewhat older version (a few months old maybe) when I first noticed the odd frame rates, but then I updated to the latest version yesterday and it still reports the same numbers.

But of course the frame rate of these DVD remuxes obviously aren't 100-600fps, so I'm wondering if there's something "off" about these files I'm putting out, or if it's just mediainfo reading them wrong. Even the mkv files put out by Make MKV are reading as 24-25 fps in Mediainfo, not 29.970. Most media players, other than mpc-be (which uses a built-in mediainfo for the file info I believe), all report normal framerates. But there must be something off about these files.

I sent an email to the creator of mediainfo and he replied back:

"Matroska does not have frame rate metadata, MediaInfo relies on an
heuristic calculation based on the first ~100 frames timestamps, very
weird results."

He asked for a short clip to analyze the video, so I sent him a clip. I'll see what he has to say about it.

[mattias83]

Something else odd - if I view some of the older DVD>MKV files I created with Make MKV in the latest mediainfo, it doesn't list those odd frame rates (like 24.062 FPS, etc.). It just lists:

Frame rate mode: Variable
Original frame rate: 29.970 FPS

But newer files I'm creating are listing the extra frame rate line:
Frame rate mode: Variable
Frame rate: 24.062 FPS
Original frame rate: 29.970 (30000/1001) FPS

Has something changed with how MakeMKV processes these mkv files?

[mattias83]

I got a reply back from the creator of mediainfo:

"Make MKV test.mkv":
Frame rate comes from statistical tags created by MakeMKV:
- duration is indicated as 5.388716666
- number of frames is indicated as 132
I just divide 132 by 00:00:05.388716666.
Report the issue to MakeMKV developer.

"Bigasoft Total Video Converter test.mkv"
Same issue, from same source, which is MakeMKV (used internally by the tool?)
- duration is indicated as 03:10:11.0663333333 then as 0:7:612 in the same tags then 0:0:5.788 in an independent tag (it is incoherent, 3 durations for the same track, and not same!)
- number of frames is indicated as 274635
So here the first issue here is that the first compute is wrong (compute would indicate 24.067), it comes from MakeMkv.
Second issue is that the remux creates stupid "5" or "7" durations, not same! the "5" duration is in the wrong place (place with stats keeping the source number of frames), the 7 is at a better place (independent, so from a remux, coherent) but is wrong (should be 5...)
But there is an issue on my side, "03:10:11.0663333333" or "0:7:612" should be used for computing, as the last one " 0:0:5.788" is in an independent tag, so something on my side. It would not change the incoherent results though (I will compute from "0:7:612" duration, or maybe from the first duration which is more coherent, or I just discard the compute because there are too many problems with this mux)


So for starters it sounds like Bigasoft is "Total" garbage and I won't trust it now. It reports the source is makemkv because I used Make MKV to output the original mkv with chapters, then I used Bigasoft to split that file by chapters, since MakeMKV doesn't allow splitting by chapter.

But he said to report the issue to the maker of Make MKV about the Make MKV test I submitted. Is this really an issue?

I made a test mkv file by just dropping an NTSC vob file into MKVToolNix and even that mkv reads a bit off in mediainfo:

Frame rate mode: Variable
Frame rate: 24.044 FPS
Original frame rate: 29.970 (30000/1001) FPS

So it doesn't seem like just MakeMKV here. Why are these NTSC-sourced MKV files reporting like this from Make MKV and MKVToolNix, and should I be concerned about the files?

[mattias83]

New replies from MediaInfo:

"Reason there are 2 issues: 1 with MakeMKV (the 24.xxx thing, also in the
Bigasoft file) and 1 with Bigasoft (it puts a good duration in a wrong
place and a bad duration in the right place).

Explanation about 24.xxx frame rate in next email."

And the follow-up email:

"OK, I got it now.
24.xxx is not far from 23.976...
And your file has REALLY a variable frame rate. Just that it is classic for NTSC, it is "2:3 Pulldown" (I let you search on the net ).
So MakeMKV is not so wrong, it stores what it counts, just me not catching the "2:3 Pulldown" so displaying as if is not known so I don't "round" the number I have for showing you something you use to see.
If I force the "2:3 Pulldown", I get:
Frame rate : 23.976 (24000/1001) FPS
Scan type : Progressive
Scan order : 2:3 Pulldown

For a weird reason I don't catch the "2:3 Pulldown"

So NTSC files are reporting correct frame rates?
But Cinema files at 23.976 fps pulldowned for NTSC in a specific way (I have files which are OK) then muxed in MKV aren't reporting correct frame rates.

Interesting, I want to report well in that case, on my todo-list but no time line, as I have more urgent things to do and they are pretty old methods and not a lot used"

"I was saying that it is wrong based on the wrong assumption that
the stream is a classic constant frame rate stream (so pure NTSC) but it
is not (it is a Cinema one at 23.976 with some frame repetition in order
to display 29.970 frames per second in average)."



So, this sounds like these are older DVDs and MediaInfo isn't taking the 2:3 pulldown into account? I'm still wondering though why some of my older files from MakeMKV don't report the frame rate line, just the frame rate mode and original frame rate? Just a different type of DVD (not using 3:2 pulldown), or could it be MakeMKV changed something about how the mkv files are tagged or how they are muxed?

[mattias83]

Another follow-up email from MediaInfo:

"Not correctly = I would not say that, just that this cheat mode on the
file side (from the makers of the DVD) is not caught in your case .

But... Yes and no: there is an issue about the precision, if MakeMKV
catches "2:3 pulldown"(sorry, it is 2:3 and not 3:2 ) it would have
more precise statistics. But I'll explain to MakeMKV author, I put you
in cc.


> I'm wondering why some of my older files from MakeMKV don't report the
> frame rate line, just the frame rate mode and original frame rate?
> Just a different type of DVD (not using 3:2 pulldown), or could it be
> MakeMKV changed something about how the mkv files are tagged or how
> they are muxed?

It is the behavior in case the statistic tags are not stored in the MKV,
I guess that MakeMKV implemented it in the meanwhile (which is a good
thing, it makes the MediaInfo output more precise; here issue is that it
is too much precise base on some issues with this crazy 1.001 typical US
stuff, like 23.976 or 29.970 frame rates not a round number)"



So it sounds like MakeMKV is not catching 2:3 pulldown correctly, and MediaInfo is also not taking it into account. He said he would contact MakeMKV about the issue.