[MPlayer-users] Creating a letterbox (PAL) VCD

[Michel Bardiaux]

Giacomo Comes a écrit :
> On Thu, Aug 30, 2007 at 02:38:18PM +0200, Colin Rosenthal wrote:
>> RC wrote:
>>> On Thu, 30 Aug 2007 11:02:10 +0200
>>> Colin Rosenthal <csr at statsbiblioteket.dk> wrote:
>>>
>>>   
>>>>     vcodec=mpeg1video:keyint=15:vrc_buf_size=327:vrc_minrate=1150:\
>>>> vbitrate=1150:vrc_maxrate=1150:acodec=mp2:abitrate=224:aspect=4/3
>>>>     
>>> No options?  You're just asking for horrible video quality.  
>>>
>>> This is all extensive covered in the docs.
>>>
>>>   
>> Well quite. The problem is that it is so extensively covered in the docs 
>> that it's rather hard to know which of the many filter options,
>> for example, might make a significant difference. For example, we tried 
>> the following two-pass encoding:
>>
>> FILTER="pp=hb/vb/dr/al/fd"
>>
>> mencoder -oac twolame -twolameopts br=224 -ovc lavc -of mpeg -mpegopts 
>> format=xvcd -vf \
>>     scale=352:198,expand=352:288:0:45,$FILTER,harddup -srate 44100 -af 
>> lavcresample=44100 -lavcopts \
>>     vcodec=mpeg1video:keyint=15:vrc_buf_size=327:vrc_minrate=1150:\
>> vbitrate=1150:vrc_maxrate=1150:acodec=mp2:abitrate=224:aspect=4/3:vpass=1 
>> -ofps 25  \
>>     -o /dev/null 070507_1210.wmv
>>
>> mencoder -oac twolame -twolameopts br=224 -ovc lavc -of mpeg -mpegopts 
>> format=xvcd -vf \
>>     scale=352:198,expand=352:288:0:45,$FILTER,harddup -srate 44100 -af 
>> lavcresample=44100 -lavcopts \
>>     vcodec=mpeg1video:keyint=15:vrc_buf_size=327:vrc_minrate=1150:\
>> vbitrate=1150:vrc_maxrate=1150:acodec=mp2:abitrate=224:aspect=4/3:vpass=2 
>> -ofps 25  \
>>     -o two_pass_filtered.mpeg 070507_1210.wmv
>>
>> but really couldn't see any improvement.
> 
> My comments about this thread.
> 
> your command line needs the following:
> remove "acodec=mp2:abitrate=224", you are using twolame so no need to set 
> options for the libavcodec mp2 encoder.
> I suggest to add vstrict=0
> You may also want to add vmax_b_frames=2 because VCD standard requires
> 2 B-frames but players should be able to play VCD without B-frames as well.
> 
> About the comments to use stereo audio:
> that's the default. No need to do anything.

Even if the input file is mono? Or worse, 5.1?

> 
> And about the video quality options:
> it depends of the source, of course, but my experience shows that adding
> mbd=2 is enough. The fact that you are forcing constant video bit rate,
> as required by the VCD standard, makes almost useless most of the options
> that improve quality. You should notice a difference if you use variable
> video bit rate (most DVD players can play VCD with variable video bitrate).
> 

-- 
Michel Bardiaux
R&D Director
T +32 [0] 2 790 29 41
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