Jeff Hyche wrote: > 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 >
If that is the formula for bpp then the bpp that transcode reports to me is some other bpp, because no matter how I massage the numbers I never get anything like what transcode reports ;^) Note also that when you are dealing with commercial dvd source, you don't know the actual quality of the source because it is typically 1/3 - 2/3 white noise added to get the material to fill the dvd. Given that, I'd say that bpp is entirely meaningless.
