Converting Audio From 23.98 to 24?

[nade281]

Hello all,

I did a mix for a client in Audition. The editor tells me that the sound is drifting out of sync. It seems that the video was shot at 24 fps but the sound was recorded at 23.98. Is there any way I can adjust my audio so it can sync with 24fps video? The editor is working in Final Cut 7.

[C.Salmassy]

Hi, Nade.

Yes, it's call "pull-up sync".  What you want to do is BATCH PROCESS your dailies audio to a NEW FOLDER.

You need to create  a new FAVORITE called Sample Rate Conversion on all of the audio so it plays 0.1% faster.  This is the process that the batch utility will execute.

1) open a test file in the waveform editor

2) select FAVORITES / Start Recording Favorite

3) select EFFECTS / Time & Pitch / Stretch & Pitch (process)

4)       a.if they are not already, set Algorithm: Audition   Precision: High

          b. under STRETCH AND PITCH check LOCK S & P (Resample)

          c. set/type Stretch to 99.9%

          d. click APPLY

5) select FAVORITES / Stop Recording Favorite

6) save the name of the new favorite process, I called mine "Sample Rate Convert + 0.1% [23.976 to 24fps]"

7) select EDIT / Batch Process to open the Batch tab

8) set Favorite: ( your newly name process)

9) click the folder in the upper left corner to select which files are to be batch processed

10) in the bottom left corner, open the Export Settings

          a. if the editor wants and prefix or postfix (ie ..._conv or   _24), add that here

          b. set the exported file location (never overwrite existing - always preserve originals)

          c. the rest of the file parameters, I would maintain; Check the "Remove Files..." option.

11) click okay; to run the batch, click RUN in the bottom right corner.

12) as a test, you can place the original of one file in a mutitrack session on track1 and the  processed version on track1 and compare how the processed gets ahead of the original

I would suggest you do a handful, send them to the editor, and wait for confirmation before batching the rest, however if you do step 12 and it's correct, you should be good to go.

By the way, I just re-read your post...thought it was dailies...everything still applies, just one file to convert instead of many.  You don't need to record the Favorite, but it is nice to have the process saved for a later application. 

The same holds true for a "pulldown" functions [24 to 23.976 / 100.1% playback rate for the conversion]

Shame on them for giving you a 23.976 when the delivery spec is 24.

Cheers,

-C

[nade281]

Thanks for the reply! It seems that did not work though, which maybe means that wasn't the issue? I've tried everything on my end, and I made sure the settings matched. The producer told me to make sure my timecode is running at 30 fps. Could this be a factor and how do I confirm this in the settings?

[ryclark]

Audition doesn't use time-code as such. It's master clock is whatever the sample rate frequency is set to in your audio hardware interface, generally 48k samples per second. Audition then just derives it's timeline read out from that, dividing by 1600 if you want 30fps or by 2000 if you want your read out at 24fps.

Your audio may need speeding up .1% as outlined above to make it match the length of the video if the speed does really differ from original audio recording. However can your editor tell you how far out it is, in frames, so that you can then calculate the discrepancy accurately against the total duration of the audio or video? When you were processing the audio did you do any editing of the audio clips? Or was it just a mixing and level setting job?

[_durin_]

Audition's Time Stretch tool can also stretch to match a specific duration, which may solve the problem without needing to do the calculations one's self.

[C.Salmassy]

Hi, again.

Here is what concerns me.

- nobody has mentioned what the Native Framerate of the original footage is: 23.976 or 24?

- if the footage was shot at 24fps, was all of the audio / video editorial done at the same rate to match? What ryclark says is true in that 48k Fs is the frequency of the clock in Audition and in FCP, and

what you were saying earlier, that you were running 48k Fs with 23.976 tc and his FCP is running 48k Fs 24tc, MAYBE his system may be seeing the 23.976 tc timestamp in the broadcast .wav file and sample rate converting it to 24 (+0.1%) when in actuality, it's not needed at all. 

- Is your client-supplied video running at 23.976 or 24? If 24, your timeline in Audition, which is set at 23.976, does it stay frame-locked with the timecode window burn in the video?

- If your video file DOES NOT have a window burn, make them resupply a video with Guide Audio and a Window Burn of the tc

Solution 2a.

Try delivering a non-broadcast .wav (turn off the metadata function) AND an .aif file (no timestamp) of your original final output. I bet the .aif file will stay in sync.

Solution 2b. (in this case, working at 24fps natively) *

- Goto EDIT / Preferences / Mutlitrack and set the Default Start Time to 59:00:00 and click OK

- Make a new Session (ctrl-N) at 24fps / 48k Fs (in the TC window at the bottom of the timeline, rt-clk and select 24fps).

- Once you have a brand new session, make sure to create a video and enough audio tracks to match the original session.

- In the audio bin, dbl-clk the original session; type ctrl-A to select everything in the session; if any of the clips are locked in time, please deselect this option now (rt-clk menu); type ctrl-G to group all media together; type ctrl-C to copy the media

- Dbl-clk the NEW 24fps session; type ctrl-V to paste all of your media into the new session - all of the clips are still in sync with each other

- Checking the video file for the first tc frame, set your point/cursor to the tc location, and with SNAP ON, grab and move all of the clips together so that the video starts at the cursor with the same tc frame in the timeline display and the video display

- Your video TC window should stay in sync with the tc display at the base of the timeline because everything is counting at 24fps.  If your timeline is drifting ahead of the video tc window at a rate of 3 frames a minute, then the video is actually 23.976 fps.

If, however, everything is in sync in your system at 24fps, then I suggest you go into Premiere with both your NEW audio export and the original video, sync the two on a timeline, dump the original audio, and export a new video matching the settings of the source video.  Give this to the client to show how everything is in perfect sync.

Needless to say,your session must be formatted to match the video file or it's going to be a nightmare, and to be honest, this should ALWAYS be your SOP at the start of any project (formatting your new session to match the client video).

If all else fails, send me a private message with your contact info, and I'll speak with you over the phone. I'll even speak with your producer...let's get this done.

[nade281]

Thanks for all your help!

Unfortunately, a solution was never found. The editor decided to fix the problem by himself by adjusting the video. I don't know it if actually worked, and it does bother me that I never found out the problem. I've done work for the same client, just different videos and have never had that problem.