Video analysis: Bit rate=13Mbps and Max bit rate=768kbps! What's going on?

I contacted Jerome Martinez of MediaInfo and received this reply . . .

On 18/01/2020 16:17, Ian Brown wrote:

This strange behaviour appears on MediaInfo and a similar app, VideoSpec

VideoSpec uses MediaInfo library, so normal.

Whenever I use a standard definition PAL video or 1080p or HDV or 4K the Maximum bit rate is always quoted as 768Kbps which seems very strange when the Average bit rate can be 13Mbps or more.

Max bit rate usually comes from a bitstream metadata, as a hint. Maybe the metadata is wrong / buggy.

I suspect that the "768Kbps" phenomenon is something peculiar to videos made on Macs as several other videos made on Windows machines don't appear to display it. Maybe the Mac video metadata has some peculiarity about it?

This is a test using different display parameters and as you can see, the result is the same. I have also seen the maximum figure of 768Kbps displayed on another bit rate question asked by someone in 2016.

Note that this 768Kbps figure appears whatever video I test it on. Yesterday it appeared on a 4K clip exported from iMovie.

Thanks Luis for the 768Kbps confirmation. It has never worried me but it has always puzzled me.

I sometimes see patterns in numbers and 768 is very significant to me . . . it's the number of pixels in a PAL Standard Definition frame ((768 x 576). Cameras shoot 720 x 576 but the pixels are slightly elongated and display as 768.

There may be no connection between the two "768" numbers but it's a mighty big coincidence!

I have downloaded a similar video info app called "Scoop" and it also displays the mysterious MAXIMUM BIT RATE of 768Mbps !

I have emailed both MediInfo and VideoSpec to see if they can shed any light on the phenomenon.