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

[Sven Brandau]

Hi Michael,

thanks for help!

Sven

Am 26.05.2010 21:55, schrieb Michael Niedermayer:
> On Wed, May 26, 2010 at 09:54:01PM +0200, Sven Brandau wrote:
>    
>> 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
>>      
> wrongly in this sense :)
>
>
>    
>> guess without the knowledge of the mpeg-2 vbv model?
>>      
> exactly
>
>
>    
>>      
>>>>
>>>>          
>>>>> 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?
>>      
> iam not aware of any vbv issues and i know some people tested streams from
> ffmpeg. Id assume they would have reported it where there issues ...
> https://lists.mplayerhq.hu/mailman/listinfo/ffmpeg-devel