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nordic bro
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Joined: 25 Oct 2003
Posts: 585
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 Posted: Mon Mar 19, 2012 5:44 pm Post subject: mkv/mp4 -> mpg, picture skips |
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I have a 50fps mkv/mp4 vid I need to convert to ~30fps mpeg2 to burn to dvd and watch on my std-def tv. I used this:
| Code: | mencoder -really-quiet -of mpeg -mpegopts format=dvd:tsaf
-oac lavc -srate 48000 -af lavcresample=48000 -aid 0 -ovc lavc -vf scale=720:-10,expand=aspect=4/3,harddup -lavcopts vcodec=mpeg2video:threads=2:vrc_buf_size=1835:vrc_maxrate=9800:
vbitrate=4400:keyint=18:trell:mbd=2:vstrict=0:acodec=ac3:abitrate=192:
aspect=4/3 -fps 50.000 -ofps 30000/1001 -o out.mpg in.mkv |
everything goes fine except for an annoying skip due to (I think) mencoder constantly dropping frames to presumably keep audio/video in sync.
the visual skipping is only noticeable during certain camera angles when something fast is moving across the screen - unfortunately it's a car race where there's lots of fast-moving things on the screen 
I tried "-noskip" which fixed the visual skipping perfectly but a/v is horribly out of sync; I tried "-mc 0 -noskip" which proved no better.
so does anyone know how I can get rid of the skipping but preserve a/v sync?
thanks.
incidentally I added some linebreaks to my mencoder code but only for posting, so my forum post wouldn't be so wide. |
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cord
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Joined: 28 Apr 2007
Posts: 344
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| Posted: Mon Mar 19, 2012 7:12 pm Post subject: |
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| Do you really need exactly 30fps in output video? If not so, and your source video scan type is 'progressive' (I guess it's your HD video camera content), you can do 50p -> 50i fps conversion (without changing timestamps) simply by dropping one field. And 50i fps is the PAL standard DVD. You can play it with any problems. |
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nordic bro
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Joined: 25 Oct 2003
Posts: 585
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| Posted: Tue Mar 20, 2012 6:12 pm Post subject: |
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| Quote: | | Do you really need exactly 30fps in output video? |
yeah unfortunately it looks like I do. my tv is non-hd ntsc and while I didn't think it would work, I tried re-encoding with -fps/ofps 50.000 and after burning to dvd it has even worse a/v skipping on the tv. |
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cord
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Joined: 28 Apr 2007
Posts: 344
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| Posted: Wed Mar 21, 2012 2:47 pm Post subject: |
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| nordic bro wrote: | | Quote: | | Do you really need exactly 30fps in output video? |
yeah unfortunately it looks like I do. |
So, in that case I don't know what to suggest you. AFAIK there is 3 variants,
1st you simply change the fps from 50 to 30 in header, and sound will be stretched down to appropriate duration (sound will be low timbre).
2nd you change fps 50->30 without changing duration (by dropping frames). Video will be strobed.
3d you don't change sound duration and don't drop video frames. You will get out of a-v sync.
ps Why you don't want to do 50p->60p->60i conversion (if you have NTSC-only hardware)? The '50-60' will be less loosing, than '50-30'  |
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