Changing Bvop default values usually increase or decrease gobal quality ?

[Zenzile]

I know that a B-frame can be encoded with higher quantizer than P-frames and get a similar quality cause they are more easy to encode but by default the x1.5 + 1 result often to a high quantizer and so, artefacts on B-frames.

Set the quantizer ratio to 1 or the quantizer offset to 0 should give better quality to Bframes but is the global quality risk to be strongly decrease ? I ask for a bitrate between 1000 and 1500 kbits.

sorry for my bad english, i do my best.

[elguaxo]

Some interesting threads that deal with this topic:

http://forum.doom9.org/showthread.php?t=96170
http://forum.doom9.org/showthread.php?p=791227#post791227
http://forum.doom9.org/showthread.php?t=119399 <- this one is even a sticky!

[Blue_MiSfit]

Indeed. Some basics:

1) B-Frames can have a higher quantizer that P-Frames, but still look good. These extra bits that you save with B-Frames can be used in the rest of the movie to increase overall quality

2) 1 B-Frame is the default, but you can usually do 2-3 without any problems, depending on your playback device. Any software player can handle as many as you throw at it, but some hardware devices only like 1 (or sometimes none).

3) Even if you select more than 3 B-frames, the encoder will rarely use more than 2 in a row.

~MiSfit