shiva-x
19th May 2003, 23:11
I dunno exactly what the "Auto determine bias setting" option in DOCCE4U does. Maybe I don't use DOCCE4U the way it was meant to, as I only do movie-only DVDs. Anyway here is an example of how I do set the bias in CCE.
Movie : Training Day R2
Running Time : 1h 57m 04s
Calculated Bitrate : 4300 kbps
First pass : ONE pass VBR :
Quantization Factor : Q40.
Min bitrate : 0.
Max bitrate : 9000.
Second pass : Multipass VBR :
1 pass
Click "Advanced..."
Global bitrate setings :
avg : 4300
min : 0
max : 9000
now let's set the bias
at first I set the bias to (AverageBitRate/100), so here it is : 4300/100 = 43.
I watch both avg and max Q factors : avg=3.35 max=3.80
I try to decrease bitrate by one unit (bias=42) : avg=3.34 max=3.86 -> I was wrong trying to decrease the bias.
I try to increase the bitrate by one unit (bias=44) : avg=3.35 max=3.73 -> great :-).
While at least one of the Q factors decreases, the other staying constant (or growing up but very little as when I set the bias from 45 to 46, the avg Q factor goes from 3.35 to 3.36 but the max Q factor goes down from 3.66 to 3.60) or both Q factors decrease, I continue increasing the bias. In this film, I had to decrease the bias until bias=50, where the Q factors are equal and minimal (avg=max=3.34).
So 50 is my optimal bias.
Imagine my bias entry value is too high, my Q factors will either gow down or stay constant when I try to decrease the bias. If both Q factors stay constant or get lower, I continue decreasing the bias until they get bigger. I had this problem encoding "Panic Room". My initial guess was way too high. My Q factors were minimal so I had to lower the bias until one of the Q factors grew up.
Using this method always gives me excellent quality results. Of course, someone can say this is because I use a very high bitrate for encoding, which is not totally wrong. Anyway I can spot the image defects when I set the bias too high (distorted images) or too low ("mosquito" noise).
I posted this thread because I think it could be a great feature to add in DOCCE4U. I think this method of smart bias setting could be automated (Or maybe DOCE4U uses this method already and I lost 2 hours writing this unuseful text :confused: ).
Movie : Training Day R2
Running Time : 1h 57m 04s
Calculated Bitrate : 4300 kbps
First pass : ONE pass VBR :
Quantization Factor : Q40.
Min bitrate : 0.
Max bitrate : 9000.
Second pass : Multipass VBR :
1 pass
Click "Advanced..."
Global bitrate setings :
avg : 4300
min : 0
max : 9000
now let's set the bias
at first I set the bias to (AverageBitRate/100), so here it is : 4300/100 = 43.
I watch both avg and max Q factors : avg=3.35 max=3.80
I try to decrease bitrate by one unit (bias=42) : avg=3.34 max=3.86 -> I was wrong trying to decrease the bias.
I try to increase the bitrate by one unit (bias=44) : avg=3.35 max=3.73 -> great :-).
While at least one of the Q factors decreases, the other staying constant (or growing up but very little as when I set the bias from 45 to 46, the avg Q factor goes from 3.35 to 3.36 but the max Q factor goes down from 3.66 to 3.60) or both Q factors decrease, I continue increasing the bias. In this film, I had to decrease the bias until bias=50, where the Q factors are equal and minimal (avg=max=3.34).
So 50 is my optimal bias.
Imagine my bias entry value is too high, my Q factors will either gow down or stay constant when I try to decrease the bias. If both Q factors stay constant or get lower, I continue decreasing the bias until they get bigger. I had this problem encoding "Panic Room". My initial guess was way too high. My Q factors were minimal so I had to lower the bias until one of the Q factors grew up.
Using this method always gives me excellent quality results. Of course, someone can say this is because I use a very high bitrate for encoding, which is not totally wrong. Anyway I can spot the image defects when I set the bias too high (distorted images) or too low ("mosquito" noise).
I posted this thread because I think it could be a great feature to add in DOCCE4U. I think this method of smart bias setting could be automated (Or maybe DOCE4U uses this method already and I lost 2 hours writing this unuseful text :confused: ).