GiP size estimates for 1080p downloads are several times too big

[Nick Payne]

I've noticed, since downloading a few programs with GiP in 1080p, that 
that the estimated download size is usually too big by a factor of 
around three or four times. This for example, is typical - the estimate 
for the dash video size is 10339MB, but the actual download is 3536MB:

================================================================================================
INFO: Downloading tv: 'Snooker: Welsh Open: 2022 - 14. The Final - Part 
2 (m00158vr) [original]'
INFO: Trying 'dashfhd1' mode: attempt 1 / 3
INFO: ffmpeg version string = 4.3.3-0+rpt2+deb11u1
INFO: ffmpeg version number = 4.3
INFO: File name prefix = Snooker_Welsh_Open-s15e14-The_Final_-_Part_2
INFO: Begin downloading at: 0.00 MB (00:00:00) [1]
INFO: Downloaded: 158.00 MB (02:42:25) [2538] in 00:31:30 @ 0.67 Mb/s 
(dashfhd1/cf) [audio]
INFO: Begin downloading at: 0.00 MB (00:00:00) [1]
   3.3%   341.30 MB / ~10339.76 MB (00:09:01 / 02:42:25) [  141 / 2538] 
@   9.4 Mb/s ETA: 02:22:13 (dashfhd1/cf) [video]
[...]
INFO: Downloaded: 3536.83 MB (02:42:25) [2538] in 01:02:04 @ 7.60 Mb/s 
(dashfhd1/cf) [video]
INFO: Converting to MPEG-TS
[...]
================================================================================================

By contrast, the estimated sizes for 720p downloads are usually accurate 
within 20% or so. This is GiP 3.29 running on Raspbian Linux.

Nick