[MEncoder-users] B-frames and GOP with MPEG-2 for DVD

[Nicolas Hesler]

Nico Sabbi wrote:
> Nicolas Hesler wrote:
>
>   
>> Nicolas Hesler wrote:
>>  
>>
>>     
>>> Nico Sabbi wrote:
>>>  
>>>    
>>>
>>>       
>>>> this -mc 0 -noskip is a myth, as far as I'm concerned: it may do some good
>>>> with -ovc copy, but not when encoding video
>>>>  
>>>>    
>>>>      
>>>>
>>>>         
>>> Really??? Good to know.
>>>  
>>>    
>>>
>>>       
>> I just did a quick test removing the -mc 0 and -noskip.  I get more 
>> errors than usual 
>>
>>     
>
>   


>> and the A-V deviates from 0.0. 
>> With -mc 0 and -noskip, I wasn't getting that deviation.
>>
>> Pos:  10.5s    253f (13%)  8.53fps Trem:   3min  35mb  A-V:0.052 [3818:223]
>>  
>>
>>     
>
> -mc 0 -noskip disables mencoder's synchronization code; that combination
> may work for some type of files, but not for many other types (e.g. 
> digital tv
> broadcast that typically have a large amount of audio preload).
> You should test the actual synchronization in the final encode rather than
> relying on those figures
>   
what errors?



I typically get these messages when encoding with -mc 0 -noskip:

ERROR: scr 0.940, dts 0.909, pts 0.951

BUFFER UNDEFLOW at stream 0, raising muxrate to 2635 kb/s, delta_scr: 167857

Without -mc 0 -noskip I get the same type of messages but also duplicate 
frame errors :

1 duplicate frame(s)!
ERROR: scr 1.642, dts 0.000, pts 1.266

and the out of sync messages:

Pos:   0.6s     15f ( 1%) 11.85fps Trem:   1min  11mb  A-V:0.058 [0:0]


Note: If I were to use format=dvd with the -mc 0 -noskip, I don't get 
any messages, which I take as a good sign. (But as I mentioned before, I 
have to use format=mpeg2 for Adobe Encore to accept the files)

If I use format=dvd without the -mc 0 -noskip, I get :

1 duplicate frame(s)!
Pos:   0.9s     22f ( 1%) 10.83fps Trem:   2min   8mb  A-V:0.084 [0:224]
Skipping frame!

Also, I'm transcoding from high bitrate MPEG-2 of 18.5 Mbs 1280x720 to 
my current avg of 6-7 Mbs at 720x480.

So, is -mc 0 -noskip still unnecessary, eventhough I'm getting these out 
of sync and duplicate frame messages?
My understanding is that the "Skipping Frame" message is a bad sign.