[x264-devel] Re: Constant Bitrate

[Loren Merritt]

On Wed, 14 Mar 2007, Alex Izvorski wrote:
> On Thu, 2007-03-15 at 14:52 +0330, Azadeh Rasouli wrote:
>>
>>  Can anyone tell me how I can have a constant bit-rate when I'm using
>> x.264 for coding? when I use x.264's option (e.g. -B 400)  for
>> running, bitrate is increased a lot (more than the time when the
>> target bitrate is not specified) and it's a lot more than the bit-rate
>> that I want to have.
>>
>> I typed :
>>
>>     ./x264 -v --b-rdo -t 2  -r 3 --frames 3 foreman.yuv -o output.x264
>> 176x144  -------> result : 372.73 kb/s
>>    ./x264 -v --b-rdo -t 2 -B 400 -r 3 --frames 3 foreman.yuv -o
>> output.x264 176x144 -----> result : 469.07 kb/s
>
> Try giving it the following options: --bitrate=400 --vbv-maxrate=400 .

--vbv-maxrate is optional. It defaults to equal to --bitrate, if vbv is 
enabled.
--vbv-bufsize is what's missing. There can't be a default value, because 
if you don't know what value you want then you shouldn't be using cbr.

That said, Manao is right. You shouldn't be using cbr in this case.

--Loren Merritt

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