[MEncoder-users] Bits per pixel, bitrate and resolution

[Joe Emenaker]

Jeff Clagg wrote:
> I don't think bpp is very useful for ANYTHING:
>   
Well, I use it for *one* thing... and you can tell me if you think that 
I'm crazy here. The vids that I download off of the net come in all 
kinds of crazy containers and formats. I like to keep them on a network 
drive so that I can get to them from all machines in the house, but I 
don't want to have to install a bunch of obscure codecs on every 
machine. So, I decided to re-encode *everything* to xvid/mp3, preserving 
resolution and bitrate of the source. I wrote a script which does 
this... but it also calculates what the resulting bpp would be and the 
script only proceeds if the bpp is within a certain range. If it's too 
high, then I figure I'm wasting bitrate on quality I'm not going to 
notice. Too low, and there was probably a miscalculation somewhere, 
since the resulting quality will probably be unwatchable.
> - if you must have a rule of thumb, you would be better served by an
>   understanding that, all else being equal, bitrate should scale in
>   proportion to the SQUARE ROOT of the number of pixels
>   
I'm intrigued! Do you have any docs that you can point me to which 
discuss the reasoning for this?

- Joe