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Old 26th January 2005, 00:18   #12  |  Link
hank315
HCenc author
 
Join Date: Nov 2003
Location: Netherlands
Posts: 570
Quote:
The Truth About Maximum Bitrate
This document was created to clear up misinterpretation of maximum bitrate.....
That's nice analogy and absolutely true!

Bitrate spikes are allowed as long as the VBV isn't "underflowed".
If your multiplexing program reports no underflows everything should be OK.

But even if a program like Bitrateviewer shows no spikes then you can underflow the VBV.
Bitrateviewer just calculates the average bitrate/second, this gives you a general idea what the bitrate looks like but if you have a few large frames in that second an underflow can occur.

You should try this:
Encode a short (20 sec) clip with a high bitrate (7000 kb/s) and load it in Bitrateviewer.
Open the video in a Hex editor and delete the first GOP, how to do that:
the file should begin with 00 00 01 B3, search for the next 00 00 01 B3 and delete everything before that string, now the first GOP is gone... save it and load it again in Bitrateviewer.
It will look different but it is the same video only the first GOP (12-15 frames) is deleted (+/- 0.5 sec. video).

Just want to make clear that it is the encoder that should make the bitstream DVD compliant by controlling the bittraffic in and out the VBV buffer.

Maybe you should take a look at my post tonight and try my (new) encoder

Last edited by hank315; 26th January 2005 at 16:11.
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