On 06/30/2006 10:35:38 AM, Phil Ehrens wrote:
I admit to having no idea what the bpp reported by transcode actually
means. When I use transcode I only ever see two values of bpp, if I
recall correctly they are 0.174 and 0.214. They seem to have no
significance when the results are examined. Somebody who knows more
about it may have something meaningful to add.
The bpp that I'm refering to is documented on page 44 of the transcode
manpage. Or atlest it's age 44 when printed out. I acutally really
only use it for a guide. If I see the bpp value as really low I might
redo it but I've pretty much got my standards down to where I want them.
Bits per pixel (bits/pixel) is a value transcode calculates and
prints when starting up. It is mainly useful when encoding to MPEG4
(xvid, divx, etc). You'll see line like
[transcode] V: bits/pixel | 0.237
Simplified said, bits/pixel quantifies how good an encode will be.
Although this value depends heavily on the used input material, as
a general rule of thump it can be said that value greater or close
to 0.2 will result in good encodes, encodes with values less than 0.15
will have noticeable artifacts.
Bits per pixel depends on the resolution, bitrate and frames per
second. If you have a low value ( < 0.15), you might want to raise
the bitrate or encode at a lower resolution. The exact formula is
bitrate*1000
bpp = ----------------
width*height*fps
