I have a question about converting 48 khz to 48.048 khz.

[Ryan Elder]

I am making a DCP of a short film of mine for festivals. I was told to convert it to 24 fps for the DCP. I did some reading on how to do that, and I was told that I would need to convert the audio from 48 khz to 48.048 khz to match the 24 pull up.

But in Premiere Pro, I don't have a 48.048 khz option to export with. Does anyone know what to do then?

[Cary Knoop]

You were misinformed, you need to keep the sampling rate at 48kHz but you need to alter the speed of the audio.

[Ryan Elder]

Oh okay, how do I alter the speed though?

[Ryan Elder]

Altering the speed also changes the pitch though, so will that be a problem? Or is there a way of altering the speed, whilst keeping the pitch the same?

[Cary Knoop]

You can resample the sound which maintains pitch but it comes at a small quality price.

Sox is a nice and free tool to change the speed and optionally remain pitch.

http://sox.sourceforge.net/

[Andrew Smith]

In context, changing the sample rate from 48khz to 48.048khz will result in the audio running at 0.999000999% of its prior speed, or something like that. Ditto for the pitch. That's close enough to 100%.

My guess is that you're not going to notice anything and neither will anyone else. Give it a test without the CPU intensive pitch-maintaining software calculated conversion and see how you go.

Andrew

[Ryan Elder]

Okay thanks, but the only way I know how to change the speed is by changing a clip on it's on. Is there a way to change the speed of the whole sequence, compared to every little audio clip individually? I tried watching some tutorials but they only talk about changing the speed on individual clips.

[Andrew Smith]

Export the audio out to a single finished file, then apply the changes to that.

Andrew

[Paul R Johnson]

Do people still produce in drop frame? I thought the NTSC days were over? Being in the UK we get very worried when asked to produce material in NTSC formats, because we have always had to guess if our converted products would actually play in the US. not at the work computer but isn't there a preset for drop frame in media encoder that converts the video AND audio as part of the conversion? I'd worry about doing any conversion as two separate files and hoping they started in sync. I'll have a look later, but I've never heard the 48+ and 48- formats even mentioned for a very long time. Is it still a common thing in the US?

[Rick Reineke]

I'm not positive about DCP, but most '24 frame' video is actually 23.976 and compatible with 48k audio. Pull up/down is not needed.. as was the case with cellulose film.

[Cary Knoop]

Originally Posted by Andrew Smith

In context, changing the sample rate from 48khz to 48.048khz......

Not sure where this idea comes from that you have to change the sampling rate to change the speed (and or pitch).

It is not true and unwise as 48kHz is the most common audio standard. Keep the sampling rate the same.

[Cary Knoop]

Originally Posted by Rick Reineke

I'm not positive about DCP, but most '24 frame' video is actually 23.976 and compatible with 48k audio. Pull up/down is not needed.. as was the case with cellulose film.

DCP is exactly 24p.

[Paul R Johnson]

thank God for that - I was imagining all kinds of crazy things happening if you had to transcode audio to package it up.

I did have a look in Premiere and Media Encoder and couldn't find any trace of this audio format - so makes sense now. 48K and leave out there!

[Patrick Tracy]

This article seems authoritative. It's a bit old as it refers to Pro Tools 7.3 as the newest version, but I suspect the issues he's discussing haven't changed.

https://www.trewaudio.com/articles/48048-khz/

[Andrew Smith]

Originally Posted by Cary Knoop

Not sure where this idea comes from that you have to change the sampling rate to change the speed (and or pitch).

It is not true and unwise as 48kHz is the most common audio standard. Keep the sampling rate the same.

Changes to duration time and pitch are a side effect of changing the declared sample rate in an audio file. It's a bit like slowing down or speeding up an audio tape playback speed. My very point was that it wasn't worth it to mess around with the sample rate and to leave it at 48k.

Andrew