[FFmpeg-devel] CBR Bitrate control in MPEG-2 video encoder

[Sven Brandau]

Am 26.05.2010 21:30, schrieb Michael Niedermayer:
> On Wed, May 26, 2010 at 09:22:18PM +0200, Sven Brandau wrote:
>    
>> Am 25.05.2010 23:30, schrieb Michael Niedermayer:
>>      
>>> cbr (constant bitrate) does not mean constant framesize
>>> the bitrate that enters the vbv should be constant
>>>
>>>        
>> And how are you measure the bitrate? In a very simple way you will take the
>> whole time of the video stream and calculate the bitrate from file size.
>> The only question is (beside the vbv constrains) how small is the time unit
>> in which the bitrate will be calculated. 1s? 30s? ...?
>>      
> you must read and understand the mpeg specs and how vbv works, this discussion
> is pointless otherwise.
>
>    

Yes ok.  :-)

But how calculate the ffmpeg cmd tool the showed bitrate during 
encoding? I guess without the knowledge of the mpeg-2 vbv model?

>>      
>>> and only a true mpeg2 stream analyzer can tell you the bitrate prior to
>>> the vbv. Your mail does not sound like you used such a tool
>>>
>>>
>>>        
>> You are right, I don't have such a tool. Have you ever tried such a tool on
>> the ffmpeg MPEG-2 video encoder?
>>      
> some people did
>
>    

Ok, and how is ensured that the ffmpeg MPEG-2 video encoder fullfills 
the specs for vbv? Was there a test with a

true mpeg2 stream analyzer and the result was fine for a set test streams?