About Reverse Telecine

The Deinterlace pop-up menu includes a setting for reversing the telecine.

About Reverse Telecine

The most common approach to distributing film’s 24 fps among NTSC video’s 29.97 fps is to perform a 3:2 pull-down (also known as a 2:3:2:3 pull-down). If you alternate recording two fields of one film frame and then three fields of the next, the 24 frames in 1 second of film end up filling the 30 frames in 1 second of video.

Figure. Diagram showing 3:2 pulldown process for distributing film's 24 frames among NTSC video's 29.97 frames.

As shown above, the 3:2 pattern (actually a 2:3:2:3 pattern since frame A is recorded to two fields followed by frame B recorded to three fields) repeats after four film frames. Virtually all high-end commercials, movies, and non-live television shows use this process prior to being broadcast.

For editing and effects purposes, it is often desirable to remove the extra fields and restore the video to its original 23.98 fps rate. An additional benefit of restoring the original 23.98 fps rate is that it is easier to convert this to the PAL 25 fps rate.

The lower frame rate also has the advantage of requiring fewer frames per second of video, leading to smaller file sizes. The reverse telecine feature makes it easy to do this.

Figure. Diagram showing 3:2 pulldown removal process, also known reverce telecine.

About the Cadence

When film is telecined to NTSC video, it has a constant cadence. This means that the 3:2 pattern is consistent and uninterrupted. It is relatively easy to remove the telecine from a constant cadence clip since you only have to determine the pattern once.

If you take these telecined clips and edit them as NTSC video, the result will be a final video file that has a broken cadence with an inconsistent 3:2 pattern. It is much more difficult to remove the telecine from this clip since you have to constantly verify the cadence to make sure you don’t inadvertently choose incorrect fields when creating the 23.98 fps video.

The Reverse Telecine feature included with Compressor automatically detects broken cadences and adjusts its processing as needed.

Other Reverse Telecine Issues

There are a few other issues to be aware of when you use the Reverse Telecine feature.

All Other Frame Controls Settings Are Disabled

Since the goal of the Reverse Telecine feature is progressive 23.98 fps video, all the other options of the Frame Controls pane are disabled when Reverse Telecine is selected.

About Reverse Telecine and Segmented Encoding

Because of the unpredictable nature of the processing when reversing the telecine, segmented encoding does not work as efficiently as it does when reverse telecine is not being used.

About Pausing the Transcode Process

If you pause the transcode process, the transcode must start from the beginning when you restart it.

Creating PAL Video During the Reverse Telecine Process

It is a common practice to convert 23.98 fps or 24 fps video to PAL’s 25 fps rate by speeding up the playback by 4 percent. If you are starting with NTSC 29.97 fps video from a telecine, you can convert it to PAL video using two jobs.

  • First job: Apply a setting to the job that performs the reverse telecine process and results in an NTSC frame size at 23.98 fps.

    Note: You could apply a setting that also converts the video to PAL; however, the format conversion will not be done using Frame Controls and may not be of suitable quality.

  • Second job: Create the second job by having the first job selected and choosing Job > New Job With Target Output. This creates a job that is chained to the output of the first job. You can now apply a setting that sets the output format to PAL and use the Frame Controls feature to ensure a high-quality output file.

    See About Adding and Copying Jobs for more information about chaining jobs.