[MEncoder-users] Bitrate question

[James Hastings-Trew]

On 11-03-31 12:33 PM, larrystotler at netscape.net wrote:
> Hi guys
>
> I've re-encoded some of my stuff using the -vf pullup,softskip option and have run into an anomaly.
>
> I have all 7 seasons of NCIS on DVD.  I re-ripped them and re-encoded them with the recommended settings for progressive videos.  The first 6 seasons are fine, and all files seem to be around the same size of about 450MB using XviD 2 pass and 1280 bitrate.  However, I have some strangeness in Season 7.  Some of the files are around 400MB.  I verified my scripts and I have bitrate=1280 specified on all episodes.  However, when I use -identify on the ones that are smaller, I get lower bitrates reported.  Episode 1 gives 1014.9kbps, where episode gives 1275kbps(which is about the average of the other season's episodes).  I re-ran the encode and got the same results....
>
> Any idea why these couple of episodes are showing lower file sizes and kbps?
>
> Episode 13 - 1037.9
> Episode 12 - 1085.8
> Episode 19 - 1180.1
>
> Thanx
It won't use more bits than it has to. If those episodes contain a lot 
of dark scenes, or a lot of scenes with more static content, or blank 
sky, etc. then they will be smaller. The fads and styles of TV 
production change... herky jerky constantly moving camera action gives 
way to more deliberate framing and more considered camera placement. A 
gritty urban look might get changed to a colour drenched "futuristic" 
look. Bright studio lighting gives way to available light or a darker 
mood. All of these esthetic changes will have an effect on video 
compression.