About reverse telecine

Telecine is the process of converting motion picture film to the NTSC video format used in broadcast television. The most common telecine approach to converting film’s standard 24 fps frame rate to NTSC video’s 29.97 fps frame rate is to perform a 3:2 pulldown (also known as a 2:3:2:3 pulldown). 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.

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 repeats after four film frames.

For editing and effects purposes, it’s often desirable to remove the extra fields and restore the video to its original 24 fps rate. This process is known as reverse telecine. An additional benefit of restoring the original is that it’s easier to convert this to PAL, the European broadcast standard, which uses a 25 fps frame 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 in Compressor makes it easy to do this conversion.

Diagram showing 3:2 pulldown removal process, also known reverse telecine

When using the reverse telecine feature in Compressor, consider these issues:

  • 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.

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

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

If you take these telecined clips and edit them as NTSC video, the result is a final video file that has a broken cadence with an inconsistent 3:2 pattern. It’s much more difficult to remove the telecine from such a clip because 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 in Compressor automatically detects broken cadences and adjusts processing as needed.

Perform a reverse telecine frame rate conversion

  1. Do one of the following:

    • In the batch area, click an output row to select a setting in a job. With this method, the modifications you make will be used for outputting only that job.

    • In the Settings pane, select a custom setting from the Custom area. (If the Settings pane is hidden, press Shift-Command-1.) With this method, the modifications you make will be saved to the custom setting for future use.

  2. In the inspector pane, click Video to open the Video inspector.

    If the inspector pane is not visible, click the Inspector button in the upper-right corner of the Compressor window.

  3. In the Video Properties section of the Video inspector, choose 29.97 from the “Frame rate” pop-up menu.

  4. In the Quality section of the Video Inspector, choose Reverse Telecine from the “Retiming quality” pop-up menu.

  5. If you’re modifying the setting of a specific job, click Start Batch to begin transcoding.

    If you’re modifying a custom setting, there are no additional steps to take.