[MEncoder-users] Audio sync problems with HDV footage while performing an inverse telecine

[Laine Lee]

On 5/3/10 1:22 AM, "Eric Wescott" <wescotte at gmail.com> wrote:

>  I have about ~5,000 HDV files recorded using an Canon HV30 Camera set to
> it's HD 24F mode. In order to get a proper 24P video file you need to
> perform a inverse telecine. I'm using the following method to create huffyuv
> files which I then transcode again into Apple ProRes for use in Final Cut
> Pro. The page
> http://eugenia.gnomefiles.org/2007/07/13/canon-hv20-24p-pulldown/ lists
> several methods to perform the inverse telecine process but mencoder seems
> to be the only one to do it correctly for me. JES-Deinterlacer produces some
> strange video artifacts..
> 
> Anyway, I'm having some issues where some of the files have audio sync
> issues. Sometimes it's just off by a constant rate like and I just shift it
> in Final Cut and it's fine. Other times the file starts in sync and then
> gradually looses sync. I'd say about 10-20% of the files have audio sync
> problems. Here is my current process
> 
> mencoder  INPUT.m2t -noskip -fps 30000/1001 -vf
> pullup,softskip,harddup,scale=1920:1080 -ofps 24000/1001 -ovc lavc -lavcopts
> vcodec=ffvhuff:autoaspect -oac pcm -o OUTPUT.avi
> 
> ALSO, If I perform a
> 
> mencoder INPUT.m2t -ovc copy -oac copy OUTPUT.mpeg
> 
> and then transcode to huffy will produce different results and sometimes
> produce a correct final output.
> 
> I've tried the most recent builds and a few older ones.. I seem to have the
> same results. I originally followed the guide at
> 
> 
> Any suggestions?


If you can copy audio with the 2nd example, have you tried it with the
first?

I've had much better success with filmdint than I've ever had with pullup.
It depends entirely on the source, of course, but what happens if you use

 "filmdint=io=30:24/fast=0,softskip,harddup,scale=1920:1080 -noskip"?

Maybe you could use Socke's ffmpeg-sox pipe that adjusts ac3 audio tempo. To
raise the pitch slightly (shorten duration), the tempo adjustment factor is
higher than 1. You have to demux and work on the audio, then remux. I put in
the brackets because the first occurrence of sox is actual (not a path)

ffmpeg -v 0 -i input.ac3 -f sox - | [/usr/local/bin/]sox -S -V -p -p tempo
1.00003 | ffmpeg -v 0 -i - -acodec ac3 -ab 448000 -y adjusted_tempo_out.ac3

Play the video and use plus and minus keys to correct audio sync once near
beginning then once near end. For example, if audio has to be moved ahead
500 milliseconds (500 on the mplayer on screen display, 5 presses of the
plus key), subtract .5 from the total number of seconds of audio, then
divide the original number of seconds of audio by that number to get the
tempo adjustment factor.

I created an AppleScript droplet to calculate that and perform the operation
that can be downloaded with the other AppleScript droplets here:

http://lonestar.utsa.edu/llee/HDTV_to_DVD.html

Laine Lee