Problem with local bitrate setting having no effect

[m1a2lt]

When using the advanced setting in CCE and attempting to do a local bitrate increase on a grey/red area, no matter how how high I set the bitrate, it never improves. This happens in about 1 out of 5 tries and usually after about 75% of the movie has been done.

A second problem I run into is when I increase the local bitrate setting for a large area of grey (usually around 1-3 minutes), the later parts that were grey are now red with some areas having a ridiculous Q rating of 56+!!!! Obviously, no matter how high I turn the bitrate setting, it stays red. What can I do to stop this from happening or is this just something you have to accept in CCE?

[RB]

Originally posted by m1a2lt
A second problem I run into is when I increase the local bitrate setting for a large area of grey (usually around 1-3 minutes), the later parts that were grey are now red with some areas having a ridiculous Q rating of 56+!!!! Obviously, no matter how high I turn the bitrate setting, it stays red. What can I do to stop this from happening or is this just something you have to accept in CCE?

This is because you didn't raise the global average bitrate as well. Think about it again, it makes sense. You have a certain global average bitrate that the encoder must keep. Now you are raising the local bitrate for some area, of course to satisfy this request the encoder has to take away bitrate from some other parts of the video. It's like having to drive 100 km with an exact average speed of 100 kmph. Of course you can drive the first 80 km at 150 kmph, but then you'll also have to drive the last 20 km at a respectively lower speed [homework: what speed? :)].

And your first problem is exactly of the same kind. After about 75% into the video, you have raised local bitrates so that the bitrate remaining for the later video parts is just the global minimum bitrate set in that same dialog. The encoder can't steal any more bitrate from there because well, it would mean bitrate for the later parts would fall below the minimum bitrate.

You see, if you have certain fixed file size for the .MPV that you need to achieve (for DVD/SVCD etc.), in which case you simply can't raise the global average bitrate, this manual bitrate tweaking really doesn't make sense. Do a standard 2 pass VBR instead and let the encoder do the hard work.