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Ryan Krickow
Bit & Sample Rate
on Aug 5, 2008 at 7:24:17 pm

I'm planning on recording the audio for an independent feature film shooting on HD at 23.98fps at 24bit 48kHz. I'm wondering what the most common bit and sample rate are for most feature films both independent and blockbuster. Is 24bit 48kHz standard? Should I be recording at a different rate? Any references to movies would really be appreciated. Thanks!


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David Jones
Re: Bit & Sample Rate
on Aug 5, 2008 at 8:00:17 pm

Don't get Ty started on bit depth...lol!

As far as I believe, 24bit 48kHz is standard.

The funny thing is that (as of right now) there are no video cameras that record audio higher than 16bit; only portable hard drives. As Ty will gladly point out, there is a big difference in sound quality between 16 and 24.


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Ty Ford
Re: Bit & Sample Rate
on Aug 5, 2008 at 9:48:24 pm

Hello Ryan and welcome to the Cow Audio Forum.

24-bit, 48 is fine for dialog and most other things. I'm sure that some folks are working above 48 KHz, but there's so much loss when you go to DVD, I'm not sure its worth it.

Even with blue ray, you have to convince me that going higher in sample rate or bit depth during production is worth it to the consumer.

::Dave. ;):

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide






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Ryan Krickow
Re: Bit & Sample Rate
on Aug 5, 2008 at 11:10:57 pm

If we're finishing on HDCAM SR I know the maximum audio quality is 24-bit 48kHz. So, if we plan on doing a film-out from the HDCAM SR tape will there be any audio problems there. Is the quality still high enough? My understanding is that it gets compressed even further when creating an optical sound track negative to be put on the print. Also, I'm very curious what most movies in the theater are using- if either of you happen to know? Thanks!



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David Jones
Re: Bit & Sample Rate
on Aug 6, 2008 at 2:56:36 am

I'm not sure anyone is doing much outputting to film anymore. The studios have gone to 2k and 4k digital for "prints" as it were. They will still supply prints on 35mm to theaters who haven't switched over to a DCP, but that will come to an end soon, too. Of course, maybe someone with more insight into this will post here.

Some info from wikipedia: according to the Digital Cinema Intiatives specification for audio, is broadcast wave format at 24 bits and 48kHz or 96kHz sampling (as I understand it, this is for projection).


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Greg Curda
Re: Bit & Sample Rate
on Oct 3, 2008 at 3:00:03 pm

Hi Ryan,

As far as I know 48/24 is the standard for HDSR. If they actually do a film out, then the mix (Dolby Digital, I assume) will also be at 48/24. The 2 track LtRt, used to make the optical track, is a collapse of the 5.1, and is compressed to fit into analog optical spec. This is (at this point) a fallback track in case the Dolby Digital fails. The optical is the same as the old Dolby Stereo, and decodes to left, center, right, surround.

G





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