performance/quality for saturated movie

[Daedalus01]

hi

with a saturated movie (1600kbps) will there be any gains from setting the performance/quality to slowest instead of standard? im thinking not at all since the movie is saturated neway, so in terms of quality, slowest will actually be worse off (tho smaller filesize)

also how do i know if a movie is saturated? is 1600kbps enough? im trying to fit 3 mov on 1 dvd but keeping the ac3 audio

[Manao]

To know if your movie is saturated, force the decoding of the movie with FFDShow, tick 'OSD', and enable 'Frame mean Quantizer'. Thus you'll be able to see what quantizer was used for each frames. If every I and P frames are at quantizer 2, it means it's saturated.

Also, since AFAIK the rate control algorithm of DivX 5.2 is working fine, if you don't reach the bitrate you were asking for, that means it's saturated.

Now, for the interest of the slow mode in case of saturation, it all depends of what is enabled by the choice of the slow mode. Better( & slower ) ME will give you some quality improvements. More accurate RD optimisations, however, can either improve or decrease quality ( depending on where and how they are used ). If it decrease quality, it should almost imperceptible, and the filesize reduction should be interesting ( if you weren't saturating the codec ).

Since I don't know the inner working of DivX 5.2, I can only guess here. The best for you, however, is to make the test by yourself.

[Daedalus01]

hmm but it will take 20hr to encode a mov in slowest rather than 3hr in standard

my understanding is that with the slowest setting something called the Rate Distortion Algorithm is activated. Basically this looks at different bitrates for encoding a particular segment, and will choose the bitrate with the best filesize/quality ratio. This means that it does not automatically choose the highest bitrate allowed, especially if a much lower bitrate can give very similar results.

therefore since this is the only extra thing happening when encoding at slow, it shouldnt make a diff if the movie is saturated because the encoder would choose the highest bitrate available anyway, and still keep under the filesize.

i thought this from reading page 51 of the official divx guide