Film, PAL and Avid



Shooting Film for PAL Post Production

Film can be shot at either 24fps or 25fps for a PAL finish. There are two ways to transfer the film to tape.

Telecine A: 25 FPS frame-for-frame from the negative or workprint. Either film that origianted at 24 FPS or 25 FPS can be transferred this way. If the film was shot at 25 FPS, there is no modification in the playrate. If the film was shot at 24 FPS, it is being played 4.166% faster.

Telecine B: 24 FPS adding a field at the 12th and 24th film frame (24 FPS film is cine-expanded to 25 frames). Film shot at 24 FPS is played at that rate with an additional frame generated in the telecine process so one second of film still plays at that duration on the PAL tape.
This means of film-to-tape transfer for PAL is not supported in an Avid Film Project. Telecine B works fine for a 25 FPS PAL video project.

PAL video explained.


The Avid Project

When setting up the Avid project you will select PAL, and 35mm or 16mm, and either 24 or 25 FPS. If you select 25 FPS, the images will play at 25 FPS (the rate they were transferred to video). If you select 24 FPS then the images will play at 24 FPS (-4.166% from the transfer rate).


Method #1

Digitizing Sound with Picture

Using Telecine A: Sound and picture can be digitized together from the video at 25fps.

In Avid PAL 24 FPS film project: Both picture and sound will play back at 24fps by slowing them down. Audio, if digitized with picture, plays back at a slower rate by dropping samples. For instance, 44.1 kHz audio plays back with a sample rate of 42.336 kHz. (In PAL projects, the pulldown switch on the Video Slave Driver is always set at x1.00).

Digital Cut back to tape offers two choices: Play at 24 FPS with pulldown field every 12 frames, or speed up 4.166% to acheive a 25fps playback.

Avid PAL 25 FPS film project: The picture and sound will have been in sync during telecine and will be captured from the videotape and played back in the Avid at 25 FPS, with no further speed corrections.


Method #2

Digitizing Sound and Picture Separately

Using Telecine A: This is a double system process where picture and sound are digitizied separately and synched on the Avid.

Avid PAL 24 FPS film project: When the preference is set, in film settings, only the picture is slowed down to 24fps and sound is not. Sound will be digitized directly from the field DAT or Nagra and are assumed to be in sync with film shot at 24fps.(In PAL projects, the pulldown switch on the Video Slave Driver is always set at x1.00).

Digital Cut back to tape offers two choices: Play at 24 FPS with pulldown field every 12 frames, or speed up 4.166% to acheive a 25fps* playback.

* the only method supported for audio mediafiles to be imported into an AudioVision or Pro Tools.

EDL's generated for this type of project will be frame accurate for the picture track and +/- 1 frame for audio. Separate EDL's need to be generated for picture and track because of this.

Avid PAL 25 FPS film project: If the film was shot at 24 FPS and telecine was done by method #1, dbl. system sound would have to be sped up by 4.166% going into the Avid Composer. Some DAT players allow speed adjustments up to +/- 6%.


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e-mail Alan Stewart.