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Converting from 30fps to 25fps?

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Jonas Bergmann
Converting from 30fps to 25fps?
on Jan 21, 2013 at 12:49:57 pm

Hello out there, hope you're having a great day, and that maybe some of you can help me out a bit:

I'm in trouble, cause I have som footage that I will have to convert from 30 fps to 25. No matter what I do I cant seem to find a way which will not either affect the sound or the picture in a bad way.

1. Is it possible for me to convert the frame rate without destroying the sound too much?

2. I will need to be able to log these file in to AVID later on, therefore; would there be any software to convert the filetypes to DnxHD?

I have tried Xilisoft, which seemed to be the best way of converting, cause it didnt seem to ruin my sound that much.

I have also tried converting the samplerate within AVID but it does not seem as I'm doing it right? Do you have any ideas on that matter?

Best regards,

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Michael Phillips
Re: Converting from 30fps to 25fps?
on Jan 21, 2013 at 2:29:35 pm

Well assuming that picture and sound need to remain in sync, the Media Composer's Mix & Match should do the trick. Open your 30fps (29.97) in its own matching project format such as 1080i/59.93, 29.97p. NTSC, etc.

Once that is done, from your 25fps project, open the 30fps bin. Media Composer automatically applies a motion adapter to adjust picture without changing original duration (sync remains). If there is still a quality issue, and you are capturing form tape sources or sources that provide an HD-SDI signal, you could look at a standards conversion with Teranex from Black Magic as your I/O device. Or have a facility do it as a service.

If you want to change the frame rate with a 1:1 or frame to frame conversion, then that is another matter. The result here would be a 20% slomo on the footage meaning if audio went untouched, it would immediately go out of sync. One could always change the sample rate to trick Media Composer into changing its time. This would be done by stripping the audio out as a BWF file, opening it in a free product like Wave Agent and changing the sample rate accordingly. I am not awake enough yet to do the math.


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Martin Jefferson
Re: Converting from 30fps to 25fps?
on Jan 21, 2013 at 9:13:42 pm

Is your footage 30 fps natively or was it shot at 23.98 and had pulldown added? If it is the latter, then perform an inverse telecine (I use Apple Compressor or Telestream Episode) to get it back to 23.98. 23.98-25 is a lot easier than 30-25. There is an audio program called Time Factory that does a brilliant job with large audio changes, but 30-25 is a 20% speed difference, and however you do it, it's going to be noticeable.

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