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

[Nicolas Hesler]

Nicolas Hesler wrote:
> Nico Sabbi wrote:
>   
>> Nicolas Hesler wrote:
>>
>>   
>>     
>>> So even if I get 1 duplicate frame (which seems to be case, in all my 
>>> videos), it could still be in absolute sync?
>>>  
>>>
>>>     
>>>       
>> yes
>>
>>   
>>     
>
> I just ran another test using a couple of different clips with -noskip 
> and -mc 0 removed and noticed the following:
>
> The duplicate frames happen at the same intervals on different clips.   
> It seems as though they always happen at 1.0s (25f), 83.4s (2002f), 
> 166.8s(4004f), and so on until near the last frames.   Can you explain 
> why it says it's skipping frames in such a pattern?  (Because my current 
> clips are small, I'm compiling a large clip to see if the pattern 
> continues). 
>
> ENABLED SOFT TELECINING, FPS=29.97, INITIAL PATTERN IS TFF:0, RFF:1
>
> 1 duplicate frame(s)!
> Pos:   1.0s     25f ( 0%)  5.39fps Trem:  10min 120mb  A-V:0.085 [7292:224]
> Skipping frame!
> Pos:  83.4s   2002f (39%)  6.01fps Trem:   8min 157mb  A-V:0.061 [5998:224]
> Skipping frame!
> Pos: 166.8s   4004f (79%)  6.01fps Trem:   2min 158mb  A-V:0.061 [5996:224]
> Skipping frame!
> Pos: 208.5s   5005f (99%)  5.99fps Trem:   0min 157mb  A-V:0.060 [5963:224]
> Skipping frame!
> Pos: 210.7s   5058f (100%)  6.04fps Trem:   0min 156mb  A-V:0.028 [5908:224]
> Flushing video frames
> Writing index...
>
> Overhead: 1.496% (2416636 / 161523716)
> Writing header...
>
> Video stream: 5908.883 kbit/s  (738610 B/s)  size: 155632964 bytes  
> 210.710 secs  5058 frames
>
> Audio stream:  224.000 kbit/s  (28000 B/s)  size: 5911808 bytes  211.136 
> secs
>
>   
OK, So now I've refined my command line a little more, I've added the 
muxrate to mpegopts (which removed the error messages I was getting) and 
I've removed the -mc 0 and -noskip until I can figure out if I have a 
sync problem or not.   The curious thing about the skipping frames is 
that my input is exactly 24fps (not 23.976) and my output is 23.976.  If 
you take the difference (0.024 x the seconds where it was skipping 
frames, you end up with almost exact integers of 2,4,6, etc.) any ideas 
on that?

BUT, I've got another problem (that it appears I've had all along with 
mencoder encodes), which I've only just discovered and that is that I 
have pulsating (grain/artifacts) frames at what I'm guessing is every 
keyint.   It's not noticeable on every video I've encoded but some 
become unwatchable. I've tried encoding with b frames and closed gop, 
but to no avail.   I've tried simplifying my command line to make 
testing for manageable but had no luck with

( mencoder -oac lavc -ovc lavc -of mpeg -mpegopts 
format=mpeg2:muxrate=10080:tsaf:telecine
-vf scale=720:480,harddup -srate 48000 -af lavcresample=48000:0:2
-lavcopts 
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=7000:vbitrate=6000:keyint=12:
trell:mbd=2:vpass=1:acodec=ac3:abitrate=224:aspect=16/9:vstrict=0 -ofps 
24000/1001 -o $output $input)

Any ideas on how to resolve the pulsating???

current command line:

mencoder -oac lavc -ovc lavc -of mpeg -mpegopts 
format=mpeg2:muxrate=10080:tsaf:telecine
-vf scale=720:480,harddup -srate 48000 -af lavcresample=48000:0:2
-lavcopts 
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=7000:vbitrate=6000:keyint=12:
trell:mbd=2:precmp=2:subcmp=2:cmp=2:dia=-10:predia=-10:cbp:mv0:vqmin=1:lmin=1:dc=10:
vpass=1:acodec=ac3:abitrate=224:aspect=16/9:vstrict=0 -ofps 24000/1001 
-o $output $input