[MEncoder-users] avi sync questions

[Wes Morgan]

On Sat, 5 Apr 2008, Jorge Peixoto de Morais Neto wrote:

>>  mencoder -oac copy -ovc xvid -ffourcc XVID -ofps 24000/1001 \
>>      -passlogfile BAND_BROTHERS_D1.log -vf crop=712:480:4:0,harddup \
>>      -aid 128 -msglevel all=-1:statusline=5 -xvidencopts \
>>      autoaspect:chroma_opt:keyframe_boost=15:max_bframes=0:quant_type=mpeg\
>>      :quant_intra_matrix=/usr/home/morganw/.transcode/intra.matrix:\
>>      quant_intra_matrix=/usr/home/morganw/.transcode/inter.matrix:\
>>      turbo:threads=1:bitrate=1500:pass=1 -channels 6 \
>>      -o /dev/null -dvd-device BAND_BROTHERS_D1 dvd://1
>>
>
> This is probably unrelated to your current problem, but there is a
> problem with your command line:
> ":quant_intra_matrix=/usr/home/morganw/.transcode/intra.matrix:\
> quant_intra_matrix=/usr/home/morganw/.transcode/inter.matrix:\"
>
> should be
>
> :quant_intra_matrix=/usr/home/morganw/.transcode/intra.matrix:\
> quant_inter_matrix=/usr/home/morganw/.transcode/inter.matrix:\
>
> Also,
> 1)Why are you using custom matrices? Where did you get these from?

Somewhere off of doom9, I believe. However, the sync problem exists 
independent of the matrices. As an aside, though, are the custom matrices 
worth the trouble?

> 2)Remove the "msglevel all=-1". Do you get any warnings?

Aside from some of the usual things you find with various dvds (framerate 
switches, duplicate frames), no errors.

> 3)Give us some information about the original movie. Framerate, for
> example. And is the original movie progressive or interlaced?

All kinds. I've ripped over 100 dvds, some telecined (to which I add the 
softskip and pullup filters), some very old movies that were encoded at 
30fps, etc. The script analyzes 1000 frames from the beginning of every 
chapter and looks for rate switches to find mixed telecine content and crop 
parameters. In the end every movie eventually loses sync, some faster 
than others.

> 4) 712 is not a multiple of 16. It is generally wise to choose
> dimensions that are multiple of 16.

To preserve as many lines of resolution as possible rather than cropping 
them. I'm aware this effects compressibility. Would it be "better" to 
scale it down to a multiple of 16 after cropping, then? Believe it or not, 
I was actually noticing the missing vertical resolution on some DVDs. It 
was a decision made during the encodefest as I examined output.

> 5) Why are you explicitly specifying "-ofps 24000/1001" ?

If I remember correctly, at some point I ran into some movies which were 
in fact 24fps but would be encoded at 29fps. The option is set from 
mplayer's "ID_VIDEO_FPS" output.

> 6) Who recommended you "keyframe_boost=15" ?

It was likely from either doom9 or archives of this mailing list. I did 
most of my research in those places.

In the past I have done test encodes with many different options, 
including of course the default options, and all had the sync issues. That 
led me to believe that the issue was independent of the video encoder 
options.

Oh, I forgot to mention, as another data point... I used to use handbrake 
to do these type of encodes, and it did not have the sync problem. However 
it has a lot of drawbacks that make it undesireable. I've also had some 
sync issues with the latest version of it as well.