PAL/SECAM Telecine

Standard PAL/SECAM Telecine

PAL/SECAM video runs at exactly 25 fps, but film runs at 24 fps.  Since the difference between 25 fps and 24 fps is so small, most PAL/SECAM films are telecined by simply speeding up the film by 4% to 25 fps.  Since the video is sped up, they also have to speed up the audio by 4%.  In addition, the audio is pitch-corrected to prevent voices and other sound effects from being too high pitched.

Do I Need to Inverse Telecine Standard PAL/SECAM Telecined Videos?

The answer to this question can be yes or no.  Unlike NTSC telecining, PAL/SECAM telecining generally does not produce duplicated fields.  However, even without the duplication of fields, interlacing artifacts can still arise.  This is possible because there are two different ways in which the fields can be arranged in a PAL/SECAM telecined video:

"Good" PAL/SECAM Telecine (no interlacing artifacts)

"Perverse" PAL/SECAM Telecine (interlacing artifacts visible on a computer monitor)

In the "good" PAL/SECAM telecine technique, all of the fields are placed in the correct frames.  This means that there will be no interlacing artifacts.
In the "perverse" PAL/SECAM telecine technique, half of the fields are shifted by one frame.  This means that fields that do not belong together are stuck into the same frame.  For example, the film field 2T will be combined with the film field 1B to produce TV Frame #1 (see the diagram directly above).  This telecine method looks fine on a television, but produces interlacing artifacts on a computer monitor.

Fortunately, the artifacts of "perverse" telecine can be corrected without any loss of detail.  If you look at the diagram directly above, you'll see that if we shift all of the top fields to the right by one frame, we'll have the correct output.  2T will then be combined with 2B, 3T will then be combined with 3B, and so on.  There will no longer be any interlacing artifacts.  Both Smart Deinterlacer and Telecide can perform the field shifting necessary to correct "perverse" telecined PAL/SECAM video.  You can download these filters from my VirtualDub Plug-ins page.

Once any "perverse" telecine is corrected in a PAL/SECAM telecined video, there are no interlacing artifacts, the file size is roughly the same, and the video plays as smoothly as the original 24 fps film.  The only disadvantage to standard PAL/SECAM telecined videos is that they run 4% faster than the original film.  For most purposes, the increased speed presents no problem.

If you did want to convert the movie back to its original 24 fps, you'd first have to use a program like VirtualDub to change the frame rate back to 24 fps.  Then you'd have to use an audio editor like Cool Edit to slow down the audio by about 4% while pitch-correcting the audio to keep the pitch from being too low.

Alternate PAL/SECAM Telecine

I have never seen this method being used, but I believe that certain cartoons and other programs use an alternate telecine method.  Basically, instead of speeding up the video, one frame is added to the video every second to change the frame rate from 24 fps to 25 fps.  I'm not sure how this extra frame is introduced, but I believe it is added through two separate fields like in NTSC telecining.  If this is true, then interlacing artifacts will be present in the video.

To inverse telecine this kind of video, you should be able to use the Telecide filter for VirtualDub.  (You can get it from my VirtualDub Plug-ins page.)

If you have any information about this kind of telecining, please Contact Me about it.