[FFmpeg-user] frame rates

[Tim Lloyd]

Hi, I downloaded a show from the BBC iplayer. I had been advised to 
expect a frame rate of 50 fps hence a high bit rate.

Duration                                 : 58 min 58 s
Source duration                          : 58 min 58 s

Bit rate                                 : 2 619 kb/s
Maximum bit rate                         : 2 734 kb/s
Width                                    : 960 pixels
Height                                   : 540 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 50.000 FPS

I don't know whether I am expecting too much. I would like to lower the 
frame rate and hence the bit rate while keeping other video aspects the 
same. I decided to ramp down to 25 fps. The first attempt changed height 
& width so I added the "-vf" qualifier. This is me clutching at straws 
so time to seek assistance.

ffmpeg -i file -r 25 -vf "scale=960:540" output

This gives me:

Duration                                 : 58 min 59 s
Bit rate                                 : 854 kb/s
Width                                    : 960 pixels
Height                                   : 540 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS

I was expecting the bit rate to drop but that seems a huge drop. Is this 
to be expected? Is there a recommended path to lower the frame rate?

Cheers