sample rate converter

NTSC sync. film is shot at 24 fps but NTSC video runs at 23.976 fps (24 × 1000 / 1001). when audio recorded at 24-fps clock plays back at 23.976 fps it drifts 0.1 % slow, and vice versa. pull-down ratifies a 24-fps capture for 23.976 playback (samples shifted to 47952 Hz from 48000). pull-up goes the other way (48048 Hz from 48000). use these only when your facility specifically needs to align the audio clock to the NTSC video clock — most modern post chains run film at 24 fps end-to-end and do not need either pull mode.