[x264-devel] achieving "contrained VBR" using crf, vbv and client buffering - wise?

[Ran RanUser]

Hello,

I don't have a vbv aware stream analyzer tool, but the following seems to
be working in my test environment when I simulate lowered download speeds.

Please let me know if my assumptions are incorrect and if I'm asking for
trouble :)

Objective:

- need to provide videos such that a user with X-kbps can view (using
RTMP/RTSP/HLS or other streaming protocols)

- achieving a "constrained VBR" effect by using crf, vbv-maxrate,
vbv-bufsize

Test:

- I want to target users that have 800kbps or higher download bandwidth
- will use 64kbps audio
- use crf 20
- vbv-maxrate=730
- vbv-bufsize=2190
- client is using a Flash player with 5 second client buffer

Assumptions:

- during any given second, the peak video bitrate  will not exceed 2190kbps
- for any 3 second stretch, the average video bit rate will not exceed
730kbps
- my client (Flash player) buffer of 5 seconds will be sufficient to handle
1390kbps additional bandwidth requirement that could occur during any 3
second period (2190 - 800kbps)

Since I don't have a vbv streaming analyzer to check, can any devs confirm
or deny these assumptions?  If this will not work as I expect, where is my
misunderstanding?  How would you achieve a "constrained" vbr encode (where
peaks must be less than X for Y period?)

Thank you, I greatly appreciate your time!
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x264-devel/attachments/20130521/c333ef15/attachment.html>