23.98 or 24fps Capture Rate for Sundance Submission

[Karim D. Ghantous]

Slight deviation from topic, but is there any problems in post caused by recording sound at 96khz over 48? Is there much of a reward for recording at 96?

You would be better off recording at 48kHz (but you can increase depth from 16-bit to 24-bit). I will say that much now, and see if I can find the article that explains exactly why. 95kHz introduces some undesirable artefacts (while bit depth doesn't).

 

[Michael Tiemann]

You would be better off recording at 48kHz (but you can increase depth from 16-bit to 24-bit). I will say that much now, and see if I can find the article that explains exactly why. 96kHz introduces some undesirable artefacts (while bit depth doesn't).

The discussion about 96KHz is slightly OT and is now being discussed here. What I'll say about that here is that if you are doing serious multi-track recording (8+ mics on a drumkit, 3+ mics on a Sarod, 6+ mics on a room, etc) and you want the summing math and other intermediate signal processing to preserve integrity at 48KHz, you want to work with 96KHz resolution. I agree that for straight-through recording->playback there is a tradeoff to be optimized between frequency response and accurate bit depth (not unlike larger pixels with lower resolution but greater S/N ratio vs. smaller pixels with higher resolution but lower S/N ratio). But once you start doing lots of signal processing, the benefits of 96KHz resolution become clear in the final masters.

 

[Joe Riggs]

Well, after 22 posts, I still don't think we have a definitive answer regarding sound recording and frame rates.

 

[Joe D'Arcy]

Hi Joe,

re: 25 to 24 conversion...

If you or someone you know has an old copy of FCP7, drag in your 25fps film & doubleclick it to load it- tools menu - conform 25 to 24 and voila! HOWEVER, duplicate your 25fps movie first before doing this & rename it @24 as this frame conversion does it at the root level & there is no going back. Going from 24 to 25 IS NOT SO EASY!!

Conform & pin the audio to 96 for cinema in Protools using a 24fps timebase QT proxy as a guide for lip-sync & bounce it as a 24bit 48khz .wav file.

You can even attach all these together into a DCP yourself for free using Open DCP if you export 24fps timebase TIFFs. Just make sure you have plenty of HDD space for those TIFFs, give yourself plenty of time to perform the JPEG2000 conversion and drag your final DCP onto a BIG .ntfs formatted USB stick (you can use the Paragon ntfs read & write plugin / 2 week free trial to do this on a Mac).

have fun!

Craig Lees
3dstories.co.uk
ED SX UK

Thanks Craig

 

[Michael Tiemann]

Well, after 22 posts, I still don't think we have a definitive answer regarding sound recording and frame rates.

Not true. Recording a good signal at 48K/24 bits is Just Fine and 48K masters deliver everything the human hear can deal with. 96K recording can, with the right microphones, pick up slightly finer details that help provide better definition for things like surround sound. More importantly, 96K audio processing is crucial for preserving the integrity of 48K phase information, so best for all mixing processes to run at 96K from start to finish, even when recording at 48K and mastering to 48K.

As for frame rates, even if Sundance were to play 23.976 fps at 24 fps (or vice-versa), the audio rate change is 1.001%, which computes to less than 1.75 cents, which is less "wrong" than are the built-in adjustments of equal temperament for the perfect fifth and its dual, the perfect fourth (which are both about 1.95 cents off). You can run into trouble if you somehow speed-adjust your audio tracks multiple times, so don't do that. Know what your true capture rate was, know what your mastering format is, and let the math do it zero or one times only.

I think the rule is: shoot HD formats (including UHD) at 23.976/48K and shoot other formats (including 4K DCI) at 24/48K. If you guessed right, you win. And if you guessed wrong, only the geekiest nerd will complain that your 2 hour shot of drying paint ran 7 seconds long or short.

As for 25 vs. 24, that's a whole different kettle of fish (and OT considering the subject line of the OP).

 

[Hrvoje Simic]

It's often done by re-timing the video and re-tuning the audio. Pretty trivial if done that way.

Audio conversion part is not trivial and can get very tricky.