Audio Pull-Down -0.1 % (NTSC)
When you work with film projects that have been transferred to NTSC, the audio must be slowed down in order to remain in sync.
Audio suffers a generation loss and speed change during the film transfer. Therefore, most audio engineers prefer to use the original tapes from the film shoot when working on a film project that has been transferred to NTSC video.
To slow down audio playback in Nuendo, you might need an external sample clock source to pull the clock speed down by 0.1 %.
For this to work, your audio card must be set to external sync and connected to the clock device via word clock, VST System Link, or some other clocking method. Furthermore, you must tell Nuendo that it is being synchronized with an external clock source. This is done in the Studio Setup dialog.
Because video and audio playback speeds are independent in Nuendo, the video will remain at the same speed while the audio is slowed down (pulled down). This ensures that the production audio and film transfer remain in sync.
Either you receive an OMF, AES 31, or OpenTL file that contains audio from the original source tapes conformed to the edited video or you have to record the source tapes into Nuendo yourself. In both cases, you have audio in Nuendo that is edited to the picture but will not stay in sync with the video unless you pull down the sample rate.
When Nuendo is running at a non-standard sample rate (47.952 kHz = 48 kHz pull-down), digital transfers into Nuendo from external equipment must be made with the external equipment locked to the same sample clock as your audio card. Most devices are capable of a 0.1 % change in sample rate and will function normally.
Any audio mixdowns that are exported from Nuendo when the sample clock is pulled down will play back in other applications and devices faster because that sample clock will be running at the standard 48 kHz.
The idea is that when you have completed the audio mix for your film project, the video will be sped back up to film speed for the final transfer back to film and your audio mix can then be played at the standard 48 kHz sample rate (no pull-down) and will remain in sync with the picture.
Using this method preserves the quality of the original audio recording made during filming and allows for a digital mixdown transfer at film speed without any generation loss or sample rate conversion.