Constant vs Variable Inconsistency with Handbrake

MKV playback, recompression, remuxing, codec packs, players, howtos, etc.
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mike_mgoblue
Posts: 80
Joined: Wed Jul 13, 2016 4:36 am

Constant vs Variable Inconsistency with Handbrake

Post by mike_mgoblue » Wed May 01, 2019 6:22 am

I recently converted several of my Marvel Blu-rays such as Thor 2, Deadpool, and Deadpool 2 to MKV. Each of them ended up with the "Constant" framerate of 23.976, which is 100% fine.

The problem is, each of those movies has "Subtitles" in them. So, I decided to use Handbrake to "Burn" the Subtitles into them. I created MKV files in Handbrake using a Bitrate that was actually 10% larger than the original file. I selected "Same as Source" for the Framerate, and I chose "Constant." Everything turned out fine. The new MKV file kept the framerate of 23.976 and was listed as "Constant" in Properties.

So, up to that point, everything was fine. ... But, I wanted to create a smaller version of the file. So, I created an MP4 version with a Bitrate of about 5,000kbs for the video and 448kbs in 5.1 for the audio. ... I once again selected "Constant" and "Same as Source" in Handbrake. But, the MP4 version ended up with a "Variable" framerate that shows a "Minimum Framerate" of 23.974 and a "Maximum Framerate" of 23.981 in each of those movies. ... I should also mention that when I made the MP4 files that were reduced in size, I did not rip from the "original" MKV files. I ripped from the new MKV files that had been cropped to the 1920x800 resolution and had Subtitles Burned into them. I actually thought that would be better, because it had the same "Constant" 23.976 framerate as the original MKV file, but it already had the Subtitled Burned in.

Any help would be appreciated. ... I'm just wondering why the consistently "Constant" framerate of 23.976 has suddenly decided to be "Variable" in each of these movies?

I'm concerned because Handbrake says that files with a "Variable" framerate may not play in all devices. Should I manually select "Constant" and "23.976" from now on rather than selecting "Constant" and "Same as Source," even though the "Source" claims to be "Constant" at "23.976"?

Woodstock
Posts: 6342
Joined: Sun Jul 24, 2011 11:21 pm

Re: Constant vs Variable Inconsistency with Handbrake

Post by Woodstock » Wed May 01, 2019 12:37 pm

Remember, this isn't the handbrake support forum...

But I use VFR same as source for just about everything in HB.

Frame rate is actually not an exact decimal number; some tools report "constant frame rate" as variable, because the intra-frame timing varies by a couple of thousands of a second around the nominal number.
How to aid in finding the answer to your problem: https://www.makemkv.com/faq/item/8

mike_mgoblue
Posts: 80
Joined: Wed Jul 13, 2016 4:36 am

Re: Constant vs Variable Inconsistency with Handbrake

Post by mike_mgoblue » Mon May 06, 2019 4:34 am

UPDATE: I found the answer.

In Avengers Infinity War, I decided to do a test in Handbrake. As a result of this test, I found the answer to the problem.

First, I did the movie in the MP4 format. As usual, I got this same "Variable" result for the frame rate, even though I had actually selected "Same As Source" and "Constant."

Then, I did the movie in MKV format. I got the exact opposite. The size of the movie was the exact same in MKV format that it was in MP4 format. However, when I went to "Properties" it showed the result as a "Constant" framerate that is "23.976." which is exactly what it was supposed to be.

Finally, I copied the MP4 format that was supposedly listed as "Variable" into an MKV format. I selected "Same as Source" and "Variable" as the Handbrake option. Yet, the results produced "Constant" results of "23.976" for the framerate in Properties.

CONCLUSION: It appears that all MP4 files produce a "Variable" framerate in the "Properties" of the Media Players I use. In comparison, MKV files seem to always produce a "Constant" result.

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