HDSLR: GH6/GH5 Why is the quality/bandwidth higher at 23.98 fps than it is at 29.97 fps?

[BobKo]

I shot a simple project today to demonstrate something for a manufacturer. I figured that recording it at 1080p MP4 was fine to show what I needed to show, so I set my GH6 to MP4/1080p. That's when I saw that the data rate of MP4/1080p is 20Mbps at 29.97 fps, but 24Mbps at 23.98 fps. Obviously, it is not a big deal... I do almost nothing at MP4/1080p. But I wonder why a higher bandwidth is allocated for 23.98 fps than for 29.97 fps. Does anyone know a logical reason why?

FWIW, the GH5 has exactly the same settings, as does the G9M2. And the quality of my "low-quality" video was really clean. It definitely served its purpose. If someone insisted that I shoot at that quality level, at least I am comfortable knowing the GH6 makes lovely MP4/1080p

 

[NorBro]

Used to be a hot topic over the years and it's been like that since the beginning of cameras (for those that do it).

There has never been an official explanation why but some cameras have inconsistent numbers for their formats and framerates.

Separately - but also related - it used to come down to what media could handle and what the box could output for the price. Meaning many cameras in the past should have had 4K/60p 2.5x the bitrate of 24p but don't (and sometimes 60p would even drop from 10-bit to 8-bit, and now more modernly 12-bit to 10-bit with applicable cameras).

For the example above, there has to be a reason as it just makes no sense for such lowly specifications in 2024, but maybe they have their reasoning somewhere out there.

 

[Chris Santucci]

I shot a simple project today to demonstrate something for a manufacturer. I figured that recording it at 1080p MP4 was fine to show what I needed to show, so I set my GH6 to MP4/1080p. That's when I saw that the data rate of MP4/1080p is 20Mbps at 29.97 fps, but 24Mbps at 23.98 fps. Obviously, it is not a big deal... I do almost nothing at MP4/1080p. But I wonder why a higher bandwidth is allocated for 23.98 fps than for 29.97 fps. Does anyone know a logical reason why?

FWIW, the GH5 has exactly the same settings, as does the G9M2. And the quality of my "low-quality" video was really clean. It definitely served its purpose. If someone insisted that I shoot at that quality level, at least I am comfortable knowing the GH6 makes lovely MP4/1080p

More fps allows for less other information. It's a trade-off. Frames Vs color information, etc.

 

[Ron Evans]

It is likely a function of the codec. In the one case it has 29.95 ( 30 ) samples per second to use to create the file and in the other case only 23.98 ( 24). They are long GOP codecs so more samples the better. I expect the real full frame samples are the same for both but there will likely be more P and B frames in the 29.97 file so less data rate. I have not tried with my GH6 but maybe 59.94 is somewhat less than twice the 29.97 data rate too.