[MPlayer-users] Two-passes encoding - What happens exactly?

[Nico Sabbi]

Alain Barthélemy wrote:

>Le mardi 01 juin 2004, 16:11:22 ou environ Nico Sabbi <nsabbi at tiscali.it> a écrit:
>  
>
>>Alain Barthélemy wrote:
>>
>>    
>>
>>>Le lundi 31 mai 2004, 16:11:22 ou environ The Wanderer 
>>><inverseparadox at comcast.net> a écrit:
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>>>
>>>      
>>>
>>>>Alain Barthélemy wrote:
>>>>
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>>>>
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>>>>>Let's have an example. I do a lot of encoding of TV signal. TV signal
>>>>>is never of optimum quality of course. Here is my instruction line:
>>>>>
>>>>>mencoder -tv driver=v4l:width=640:height=480:amode=0 -ovc lavc 
>>>>>-lavcopts vcodec=mpeg4:vbitrate=1800:mbd=2:acodec=mp3:v4mv -oac 
>>>>>mp3lame -lameopts cbr:br=96:mode=3 -vf crop=620:460,pp=tn/lb,scale 
>>>>>-zoom -xy 640 -sws 1 tv:// -o movie.avi -endpos <sec>
>>>>>
>>>>>I am not original. I just try what I read on the list.
>>>>>    
>>>>>
>>>>>          
>>>>>
>>>>Any particular reason you don't use -oac lavc -lavcopts
>>>>acodec=mp3:abitrate=96:... ? Do you just really need mono sound?
>>>>
>>>>-- 
>>>>    The Wanderer
>>>>  
>>>>
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>>>What does abitrate=96 do here? If I read the manpage, I see: 
>>>
>>>abitrate = <value>
>>>  Audio bitrate in kBit (default 224)
>>>
>>>What does it do with mono/stereo sound and there is always a default value 
>>>(224).
>>>
>>>Why 224 as default? Why not 128 as default?
>>>
>>>
>>>
>>>      
>>>
>>because the default codec is mp2 (which compresses much less and worse), 
>>not mp3
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>
>Now one answer leads to another question. I was talking about default abitrate
>and you talk about default codec. What is the task of -oac mp3lame -lameopts
>...? I thought lame encoded with mp3 as audio codec (at least in my setting).
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it does, and as far as I know using -oac mp3lame is the only way to 
encode to mp3: when I posted the patch to encode audio
using libavcodec acodec=mp3 was not accepted 
(avcodec_find_encoder_by_name() failed).
Maybe now libavcodec has some bridge code that calls lame to encode audio??