24P Workflow from HDW-F900 (CineAlta) Cameras and Avid Editing Systems (24p Project type)

24FPS

23.976FPS

Camera is shooting at true 24 frames per second. This is the main method of working for a PAL postproduction workflow where NTSC is also needed. The production may also choose to acquire at 25P. The decision here is to decide where the 4.1% change should occur: for the PAL or the NTSC release. Working with the camera at 24fps is exactly the same as working with a film based workflow minus the film to tape transfer of course.

 For NTSC postproduction workflow, the production can decide to shoot at either 23.976fps or 24fps. The decision to work one way or the other is largely dependent on the audio processes desired downstream. 23.976 is used since it matches the resulting rate of film once transferred to tape. It is not recommended to use 23.976-acquisition rate if a PAL postproduction process is planned.

If using double system process on the set, the camera and the DAT can both be recording 24-frame timecode creating a 1:1 sync relationship between the picture and sound. This is also the method used in film production for PAL post processes.

If using double system on the set, the DAT recorder does not have a 23.987 timecode rate. Set the DAT recorder to 29.97 fps, non-drop timecode. Keep in mind that 29.97 is the speed of the recording. Drop and non-drop are both available as a counting scheme.

The Avid editing systems are based on a true 24-frame workflow. They can digitize audio that is reference to either 24fps or 23.976. Once digitized, all playback is resolved to 24 frames per second. 24 fps = 48kHz. When DAT recording is in sync with 24 frame per second picture, the audio can be digitized via the digital AES/EBU. The DAT deck needs to be set up to generate 30-non-drop timecode from the internal 24-frame timecode used on the set. When digitizing via the AES/EBU, the audio pulldown switch is ignored since all sync information is contained within the signal. Only when digitizing via analog inputs does the audio pulldown switch affect the digitize process. Keep in mind the downconversion process issues when dealing with true 24fps to NTSC. Please refer to this.

It is believed that for PAL, the DAT 25 frame timecode generation from the 24 frame source is NOT the same process used by the HDW-F500 VTR during the down conversion. The resulting timecodes will not have a common timecode. 24p.com will conduct further testing in this area and update this page when completed.

Digitizing via the digital AES/EBU is not possible in Avid editing systems when the audio is in sync with a 23.976 source. The audio must be digitized via the analog channels with the pulldown switch set to .99.

One can choose to use the Zaxcom Cameo SV, a mixer for audio I/O that will do sample rate conversion on the fly. Using this, will allow user to digitize picture and sound as AES/EBU.

In this case, both the down converted NTSC dub from the 24P original and the audio will have the same timecode. If digitizing double system, AutoSync can be used to sync the picture and sound based on the common timecode.

If picture and sound were recorded directly to the original HD source tapes, then the audio setting is .99 and analog input channels must be used.

Once clips have been synchronized, the user then needs to recreate the original 24-frame timecode that exists on the HD 24p tapes. The "Start" timecode column reflects the timecode of the source from which the clip was digitized. In NTSC it will be 30 non-drop or drop (although non-drop should always be used for 1080p/24 down conversions to NTSC) and 25 fps for PAL. The auxiliary timecode columns are used to track alternate sources or compensate for offset errors. In this case, the user will need the "TC24" column. The user highlights the "Start" timecode column and then performs a "command D" or "Control D" depending on platform. A small dialog window will appear asking into which column should this information be "pasted." Scroll down and select "TC24" from the list. During the "copy/paste" function, the system recalculates the original 24 frame timecode based on the same rules as the down conversion from the HDW-F500 VTR:

1. NTSC – undoes the 2:3 relationship between 24 and 30 (see table)
2. PAL – recalculates from 00:00:00:00 the number of frames based on 24 instead of 25.

The Avid editing systems can track for a single 24 frame sequence, the original 24fps timecode, the NTSC timecode as well as PAL and PAL pulldown for both source and record.

EDL Manager 10.0 will generate 24 frame EDL’s from these sequences. Please refer to the EDL Manager User’s guide for more information. EDL Manager 10.0 will also generate a "digital Cut" EDL which inserts the proper field identification of the pulldown phase. This is also appropriate for 1080p/24 down converts to NTSC. This information can important to downstream processes such as tape to tape color correction and MPEG2 encoders.

24/30 timecode relationship for 10 frames (see chapter 7, Digital Filmmaking for full description)

24

30 (frame + field)

:00

:00.1

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:00.2

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:01.1

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:01.2

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:02.1

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:02.2

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:03.1

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:03.2

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:04.1

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:05.1

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:06.1

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:07.1

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:08.1

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:10.2