GiP can help with reducing output bitrate but this is achieved by using
a custom command for ffmpeg (either on the command line or embedded in
the appropriate preset)
We've found the following ffmpeg flags help considerably:-
-> Reduce frame rate by half using: -r 25
https://trac.ffmpeg.org/wiki/ChangingFrameRate
-> Reduce the output bit rate using combo's of: -b:v -minrate -maxrate
-bufsize
https://trac.ffmpeg.org/wiki/Limiting%20the%20output%20bitrate
The first suggestion will easily result in an appreciable reduction in
output size for a modest hit on encode times.
The second can help further but comes with significant computational
overhead (i.e. time) as well as producing a subjectively better/worse
result. This means some experimentation!
To find out, try ffmpeg on the command line with short stretches of
video (~10-15mins) to see how different material performs - there will
be different results for natural, studio, film, live & CGI material.
How to implement custom ffmpeg command is given in the github wiki.
HTH
On 20/09/2022 16:29, D Martin wrote:
Hi all. Neither a newbie nor an expert here, so I feel the need to
ask all you experts ...
A few months ago I realised that better resolution video was possible
by using dashfhd1, than what I'd previously been using.
It works well and the 1920 x 1080 video is lovely.
It does take up a lot of space though, and now I'm seeing 2:1 space
differences between different programs recorded the same way. Three
examples below ...
PID Type Name Episode Versions Duration Channel Time Added Filename Mode
First this is THE REPAIR SHOP, file explorer shows 1.39GB, 28mins50
secs, 1920x1080, 6901kbps, 50fps,
b09wv7ck tv The Repair Shop: Series 2 04. Episode 4 original 1730 BBC
One 1d 15h ago
H:\New_Audio\The_Repair_Shop_Series_2_-_04._Episode_4_b09wv7ck_original.mp4
dashfhd1
Second this is FAKE OR FORTUNE, file explorer shows 1.67GB,
58mins14secs, 1920x1080, 4099kbps, 50fps
m001c26z tv Fake or Fortune?: Series 10 04. Flemish Old Master
audiodescribed,original 3540 BBC One 6d 0h ago
H:\New_Audio\Fake_or_Fortune_Series_10_-_04._Flemish_Old_Master_m001c26z_original.mp4
dashfhd1
Third this is SAVING LIVES AT SEA, file explorer shows 3.20GB,
58mins45secs, 1920x1080, 7790kbps, 50fps
m001bvr8 tv Saving Lives at Sea: Series 7 03. Caught Out
audiodescribed,original 3540 BBC Two 3d 21h ago
H:\New_Audio\Saving_Lives_at_Sea_Series_7_-_03._Caught_Out_m001bvr8_original.mp4
dashfhd1
So summarising .
REPAIR SHOP1.39GB 29mins 6901kbps
FAKE OR FORTUNE 1.67GB 58mins 4099kbps
SAVING LIVES .. 3.20GB 59mins 7790kbps
Clearly the kbps is the critical factor. So I guess this is quite
outside my/our control? Or is there a way I can ask get_iplayer to
downrate the SAVING LIVES AT SEA recording (for example) so that it
still saves at 1920x1020 resolution, but at a lower bitrate?
Thanks all ... David
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