[MEncoder-users] x264: vbv bufsize

[Nicolas Hesler]

Loren Merritt wrote:
> On Thu, 6 Dec 2007, Nicolas Hesler wrote:
>
>   
>> What is the vbv bufsize exactly and how do I calculate what size it
>> should be?
>>
>> Let's say for bitrate 3000 and vbv_maxrate 4500
>>
>> or
>>
>> bitrate 3000 and vbv_maxrate 9500
>>     
>
> vbv bufsize is the amount of memory a constant bitrate decoder needs to 
> allocate to buffering the incoming compressed bitstream. You don't 
> calculate it. There are 4 possible cases:
> * You want to target a specific hardware deocder, and its documentation 
> says what bufsize it uses. Copy that size.
> * You want to target a specific hardware deocder, and its documentation 
> doesn't say what bufsize it uses. You're screwed.
> * You want to stream to a generic software player. Any bufsize works, but 
> the end user needs to specify the same (or larger) bufsize when playing. 
> It's a tradeoff between quality and latency, and there are no rules for 
> choosing an optimal value, any more than there are rules for choosing an 
> optimal bitrate.
> * You aren't streaming nor targetting a hardware decoder. Don't use 
> constant bitrate.
>
> --Loren Merritt
>   
Thanks.  That clears that up.  But how do you set min and max bitrate on 
a variable bitrate encode with x264?