Conversion Method for 96KHz to 48KHz Production Recordings, preserving original TC

[jeremiahmoore]

Conversion Method - 96k to 48k Production Recordings, preserving original TC: For those days when you record your production sound at 96 but need to deliver in 48, whether on purpose or accidentally. 

 

The below is written for Mac users; I'm not sure if Wave Agent or Twisted Wave are available in other platforms. 

 

Wave Agent is free and is from Sound Devices

Twisted Wave has a batch processor, and is available on the web; commercial and reasonable though I think is subscription at this time, it's my understanding licenses are perpetual if your subscription expires. 

 

OUTLINE:

Issue is: TC is calculated based on samples since midnight / at frame rate. Therefore, a straight sample rate conversion results in metadata being off by huge amounts. The timecode calculation must be updated to match the changed sample rate. 

References:
    See "Editing Sampling Rate and Frame Rate" in page 15 of Wave Agent users guide: 
   https://cdn.sounddevices.com/wp-content/uploads/2019/04/waveagent_en.pdf

 

WORKFLOW:

In Finder
    - make dup / temp copy of sounds, because we're going to change the metadata and write the changes into them. This is an intermediary step and these can be deleted when done. 

 

in Wave Agent
    - Scan 96k files into WaveAgent
    - Take Note of correct timecodes for file starts. Perhaps shoot a screenshot for reference. 
    - set "Preserve Start TC" checkbox to ON
    - change Sample Rate to 48000
    - (NOTE:  Timecode entries will appear wrong, as they are being calculated using sample since midnight, but using a different sample rate; once this is changed back via resampling, the TC will be corrected.  Also: Sounds will play at half speed.)
    - click "Save" on all sounds
    - set "Preserve Start TC" checkbox to OFF
    - change sample rate to 96000
    - click "Save" on all sounds
    - (NOTE: We've now updated the timecode to be at the 48K rate, but rewritten the headers to be at the 96k origination sample rate.)

in Twistedwave
    - load into batch
    - set SRC to run 96k to 48k conversion
    - do any other processing such as limiter from 32bit to 24bit
    - save in WAV

back in Wave Agent
    - check timecode 
    - check that sounds play properly

in Finder
    - delete temp copies of sounds w/ changed metadata. 

 

 

 

[jeremiahmoore]

Method 2: Soundminer Mirror

 

I've yet to test this personally, but Justin Drury the developer of soundminer has confirmed that SM recalculates the starting timecode of any sounds resampled in SM, including on delivery and mirror.  

Steps would be:
- scan to WaveAgent to check timecode of source files. 
- scan to Soundminer (use a dialogue database to ensure all necessary fields are there)
- run mirror to convert to desired output format
- scan mirrored files into WaveAgent to validate correct Timecode metadata. 
 

Please note: Soundminer is expensive commercial software. 

It's used fairly commonly in Audio Post to manage sound libraries. 

 

-jeremiah