Sample Rate and Frame Rate Settings for Production Sound

Q: What sample rate & frame rate should I set my 702T/744T to when recording sound for picture? The short answer. . . Set sample and frame rate to what pre-production tells you (and get it in writing!) This may appear to be an attempt to ‘pass the buck’, but in actual fact this is, as you will appreciate as you read further, the most important recommendation in this Sound Note. A production’s choice of sample rate and frame rate depends on numerous variables including, but not necessarily limited to:
  • picture acquisition media format (film, SD or HD Video),
  • picture editorial project frame rate (24p, 23.976p, 29.97, 25, 30 etc).
  • delivery format (theatrical film release, NTSC TV , PAL TV or combination),
  • production budget,
  • sync dailies method (in telecine or AVID/FCP),
  • sound post edit and mix preferences,
  • manufacturer and software version of non-linear editing systems to be used (AVID, FCP, PROTOOLS, NUENDO etc).
In addition, one of sound post production's main concerns is maintaining the cleanest digital audio signal path from acquisition, through transfer, sync dailies, edit, mix and layback to deliverable master. Therefore, they devise a workflow with the primary goal of avoiding or reducing occurrences of sample rate conversion or analogue transfer. These factors make it nearly impossible to outline a definitive set of sample and frame rate rules that will guarantee problem-free post production in all scenarios. Each workflow has its advantages, compromises and drawbacks. Therefore, it is up to each production to decide, in collaboration with their technical departments, the best way to proceed in order to meet budget and deliver final product in the required formats on time. Unfortunately, answers are not always forthcoming from pre-production prior to shoot, perhaps because the post house’s capabilities and requirements are not known on day one. If this is the case, listed below are a few basic guidelines to get you underway. Be aware, however, that there are a range of other possibilities that may better suit a particular production's workflow.

Setting Guidelines

  1. As stated earlier, if at all possible, you MUST try and confirm your selection with pre-production or post. These are only general guidelines, NOT rules. There will always be exceptions.
  2. Audio for film and TV broadcast should always be recorded at 48 kHz or one of its variants, 48.048 kHz and 47.952 kHz. If you have been instructed to shoot at 48.048 kHz or 47.952 kHz, always select the ‘fake’ stamped sample rates of 48.048F or 47.952F respectively unless otherwise instructed by pre-production.
  3. If you are about to shoot and you have been unable to get any information from pre-production, use the following suggestions to determine which sample rate / frame rate combination to use. These will provide post with the greatest flexibility. 48k / 25 If picture is to be shot at true 24 or 25 fps and is to be edited in a PAL video environment. 48k / 30 If picture is shot at true 24 fps and to be edited in an NTSC environment. 48k / 29.97NDF If picture is shot on video at 23.976 or 29.97 and to be edited in an NTSC environment.
  4. Although 23.976 and 24 fps frame rates are being used more and more for sound rushes, do not use them without express permission from pre-production.
  5. Do not use DROP FRAME rates without express permission from pre-production.
Have fun!