PAL Timecode for Film and 1080p/24 Production

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There are some simple rules to follow for PAL based film and HD 24p production when it comes to the use of timecode. The choice of timecode rate of course relates directly to the frame rate chosen for the production. But in the case of double system production where picture and sound are captured on separate recording devices, the post production use of the timecode will differ based on the transfer and frame rate of the chosen post production workflow.

Production

For production, the timecode always matches the rate of the capture frame rate. Even when working with double system sound. Unlike NTSC double system production, where the film rate and the sound rate have different timecode stamps, PAL should always use the same timecode rate for picture and sound.

For 25 frame productions, there is no issue since it follows standard PAL production practices. It is assumed that the entire process will be at 25fps and not discussed any further.

It is recommneded that a 24-frame rate capture should always use 24-frame timecode, even for audio. This is true for timecode on film such as the Aaton timecode system or the Arriflex timecode system as well as 1080p/24 HD production using a camera such as the Sony HDW-F900. Doing so will allow the most flexibility for postproduction workflow. More information at Aaton Timecode. It is possible to time stamp the audio with 25 frame timecode, but this limits the post production to only using a "PAL Method 2" workflow (Avid workflow term). This can, in some cases, be more limiting whereas the 24 frame timecode allows the choice of "Method 1" and "Method 2."

Time stamping the production audio at 25 frames, is is essence the same concept of letting the DAT playback machine create 25 frame timecode from 24 frame sources. The relationship is the same between the original picture at 24 fps and audio at 25fps. It is just being moved earlier into the production cycle.

It should also be noted that "dead-on" sync is only achieved at the top of every second, when audio sources are brought into an Avid editing system. Sample-based DAW synching systems like the Aaton InDaw can rework the sync relationship between the picture and sound. Unlike NTSC, where "dead-on sync is achieved every 1/6th of a second with a known 2:3 pulldown relationship.

Postproduction

Film to tape

When 24-frame captured material get transferred to video, the material is transferred at 25fps increasing the playback rate by 4.1%. This allows the video to have a 1:1 relationship with the film. During this transfer, the 24-frame timecode now counts as 25-frame timecode, making it usable in all postproduction editing systems. The only issue is the pitch of the transferred audio. It is now raised by .7 semitone.

If a 25-frame timecode were used during production for audio, the sync transfer would raise the 25-frame timecode to a 26.025 timecode rate rendering it useless.

Down-conversion

When down-converting from a 1080p/24 production, the Sony HDW-F500 VTR converts the timecode to 25fps by recalculating the timecode from 00:00:00:00. If audio were recorded single system with the Sony HDW-F900, the down-conversion would retain the 48kHz-sample rate, but the pitch would be raised by .7 semitone.


Editing (Avid systems)

When working with Avid editing systems in a 24 frame project type, the user can choose to work in either a PAL Method 1 (PM1) or PAL Method 2 (PM2). In systems previous to version 10 (Media Composer) and version 3 (Symphony and Symphony Universal), this selection was done in the "Film Settings." In the latest release, PM1 and PM2 is done at time of project creation.

PAL Method 1 allows picture and sound to be digitized at the same time and it is assumed that picture and sound are in sync at time of digitize. All sources are 25-frame timecode and all EDL creation will reflect these sources. During the editing process, all playback is done at 24 frame rate for playback. This is achieved by slowing up both picture and sound. EDL's can be created to track the digitizing sources as 25 frame timecode as well as 24 frame timecode to reflect a 1080p/24 down conversion (see here).

PAL Method 2 allows digitizing of picture and sound as separate streams and assumes that the audio being digitized is in sync with the original 24-frame capture. During playback, the Avid editing systems, only slow down picture to match the sync sound. This method is the preferred method when the digitized audio files are going to be used for the final audio mix via an OMF process.

Since the Avid does not yet support 24 frame timecode directly, to get the original audio with 24 frame timecode into the Avid, the user must set the DAT Player menu to create 25 frame timecode from the original 24 frame timecode. Re-dividing every second into 1/25th instead of 1/24th does this. The audio does not get played back at a faster rate thus is not subject to a pitch shift. The sample rate also stays at the original sampling rate. This is similar to the PAL pulldown process or PAL +1 method for picture, where 24-frame film is transferred to 25-frame video by adding 1 field every 12 frames. It should be noted that the 25-frame timecode conversion done by the Sony DAT players is not the same timecode conversion done by the Sony HDW-F500 VTR.

EDL creation needs to be done separately for both picture and sound in order to reflect the original sources accurately. Version 10 of Media Composer and version 3 of Symphony and Symphony Universal allows tracking of the each of these types of timecodes. The picture EDL will be generated from the "Start" timecode column. The audio in a PAL method 2 can be created from the "TC 25PD" column which counts as 25 frame pulldown, similar to the DAT player timecode conversion. For Digital Audio Workstations that can take in a 24 frame EDL, the same EDL described for the down conversion process below can be used for the audio as well as film timecode.

Picture EDL from a 1080p/24 down conversion is created via the "TC 24" timecode column which recalculates the "Start" timecode from 00:00:00:00 similar to the HDW-F500 VTR. This EDL creation is covered in this resource paper.