[x265] Dynamic rate control

[Mario *LigH* Rohkrämer]

Am 13.10.2015, 15:50 Uhr, schrieb Ralf Globisch <rglobisch at csir.co.za>:

> Joshua, just checking if I'm understanding you correctly: are you  
> suggesting I change the x265_param::vbvBufferSize parameter before  
> calling x265_encoder_reconfig?
>
> Currently I am only setting x265_param::bitrate. If I need to set  
> vbvBufferSize what > sort of values should it contain in relation to
> the desired bitrate in kbps?
>
> Thanks,
> Ralf

The "Video Buffer Verifier" is a system to tell the encoder the maximum  
capacity of a decoding buffer and the maximum speed this buffer can be  
filled. In consumer players, it relates to the capacity of RAM built in to  
use as the decoding buffer (for DVD Video players, it used to be 224 KB =  
112 DVD sectors with 2048 bytes each) and "1x" DVD drive reading speed  
(9.8 Mbps data netto). Blu-ray has a considerably higher capapcity and  
limit values, just don't remember without searching... Guides for x264  
recommend '--vbv-maxrate 40000 --vbv-bufsize 30000'.

In case of network streaming, you can define both vbvMaxRate [kbps] to the  
estimated available bitrate in your network (maybe with some overhead, *  
0.9), and vbvBufferSize [kbit] to the amount of data required to fill a  
buffer for a desired number of seconds (e.g. 5 s * vbv_maxrate). This may  
guide the bitrate control more certainly to stay in the range you need;  
but it will take time to adapt, if it works at all...

No warranties.

-- 

Fun and success!
Mario *LigH* Rohkrämer
mailto:contact at ligh.de