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-   -   KVCD: Frame Rate conversion? (http://www.digitalfaq.com/archives/encode/2607-kvcd-frame-rate.html)

serrabastien 02-14-2003 03:56 AM

KVCD: Frame Rate conversion?
 
Hi all,

i would like to convert some divx to kvcd but i have one question concerning the frame rate. My dvd player is a PAL version so i think i have to convert the frame rate to 25fps. How do you do that ?

I've made one try : the frame rate of the divx was 23,976. Then before encoding i've changed the destination frame rate to 25 to match with PAL standard. But the final mpg appears to have one "artificial" frame inserted each second (which sounds logical in fact) :( . It's a bit irritating !!! :cry:

Please help !!!

Thx

Fiz 02-14-2003 04:11 AM

Hi Z

You should find that your player will still play NTSC KVCD movies so there should be no need to convert the framerate! Most players have support for both PAL and NTSC (as part of the VCD 2.0 standard).
If it shows black and white, use the s-video out or RGB scart output to your TV. :)

If you are still not convinced it works then you can use the AssumpeFPS function in Avisynth.

The command is:

AssumpeFps(25)

just below your AviSource line. Then encode as PAL in TMegEnc. You need to ensure your audio is sped up slightly as well. :wink:

Cheers.

serrabastien 02-14-2003 04:23 AM

thx, i'll try in NTSC.
But in that case i must use NTSC picture format i think (480x480 not 480x576 for example).

Does the assumeFPS fonction give good results (no jeerky picture) ?

Fiz 02-14-2003 05:17 AM

Quote:

Originally Posted by Z
But in that case i must use NTSC picture format i think (480x480 not 480x576 for example).

Thats correct. I've never actually tried mixing resolutions with video formats but better to be safe! :wink:

Quote:

Originally Posted by Z
Does the assumeFPS fonction give good results (no jeerky picture) ?

It should be smooth as it speeds the movie up slightly to make 25fps instead of 23.976. The audio frame rate also needs to be converted.

serrabastien 02-14-2003 05:21 AM

Quote:

Originally Posted by Z
[...] The audio frame rate also needs to be converted.

How ?

Fiz 02-14-2003 06:14 AM

Download BeSweet and BeSweet GUI (you can grab it from Doom9.org). Its an audio format converter like HeadAc3he and has the option to change the frame rate for the audio.

The other option if your divx source has mp3 audio, you could try this. Add the line "EnsureVBRMP3Sync()" after the line for AssumeFPS.

e.g.
AviSource("c:\myfile.avi")
AssumeFPS(25)
EnsureVBRMP3Sync()

Load the AVS into Virutal Dub. Extract the audio (it will save as WAV format and will be quite large!) Use Headac3he as normal to convert WAV to MP2. I haven't ever done this myself but it's worth a try. Whats life without experimenting :wink:

Jellygoose 02-14-2003 09:00 AM

I don't think EnsureVBRMP3Sync() will speed up the audio just like BeSweet... I think it's for the purpose to keep audio in sync when encoding from VBR MP3 to constant bitrate.

Fiz 02-14-2003 09:20 AM

Quote:

Originally Posted by Jellygoose
I don't think EnsureVBRMP3Sync() will speed up the audio just like BeSweet... I think it's for the purpose to keep audio in sync when encoding from VBR MP3 to constant bitrate.

Jellygoose, I agree, but ... EnsureVBRMP3Sync() is also used for CBR mp3s when the the trim function is used to maintain sync with the video. I was just wondering if it can keep the audio in sync with video even if it the video was sped up. (Thinking about it, maybe it should be before the Assumefps() statement.) I'm pretty certain it won't work, but it was just a thought. :wink:

BeSweet will definitely do it though. :D

Gaudi 02-16-2003 01:58 PM

Quote:

Originally Posted by 'Z
Quote:

Originally Posted by Z
[...] The audio frame rate also needs to be converted.

How ?

Well, I have been using this technique to convert from PAL movies into a NTSC KVCDx3.
Use the AssumeFPS() filter to change the video stream playback rate. And then, extract the audio with VirtualDub as mp3 (or anything else) and use this command for BeSweet encoding. It will do a flawless length conversion.
Using this my movies ALWAYS keep in sync:
  • BeSweet.exe -core( -input "YourInputFile.mp3" -output "YourOutputFile.mp2" -logfile audio.log ) -ota( -g max -r 25000 23976 -shibatch( --rate 44100 ) ) -2lame( -e -b 128 -m s )

Note the bold part, that is the command that perform the FPS conversion for the audio file. You can change all other options as you like so as to encode to different samplerate, etc.
Remember that the pitch will change a little (no matter if going from 23.976 to 25 or the other way round, but will be noticeable if the difference is bigger).


Gaudi


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