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User Manual : Optional Plug-ins
User Manual
242
Time Stretch and Pitch Change for Film Applications
There are three main categories of Cinema time stretching and pitch changing requirements:
1) Conversion of audio rushes from 24 to 25 or 25 to 24 when their associated video or film has to
be sped up or slowed down. The main reasons are:
a. The shooting has been done with film AND video, so one part of the rushes or the other have to
be sped up or slowed down.
b. The telecine process to bring the film rushes to video for editing didn't preserve the original speed,
intentionally or by mistake.
c. The shooting has been done on video at 25fps (intentionally or by mistake) and has to go to film.
Pyramix provides various solutions to this problem:
Batch conversion
of a whole media folder. Just select all media to stretch/squeeze / pitch change and select the menu
Quick Convert > Prosoniq MPEX2 module. All media will be processed in one shot. Media will have to
be re-synchronized in time with their video equivalent by using the reference "Clap".
In the case where all the media are already synchronized in time with their video equivalent (either man-
ually or because they've been properly stamped while recording), then simply send all these media to
their original TimeCode (time stamp) in a Pyramix project and select the menu item Project > Stretch /
Pitch. All media will be properly stretched/squeezed and their position will be also correctly updated.
The new original TimeCode (time stamp) can then be written back to the media by selecting the menu
item Clips > Operations > Update Media Original TC, so these new media can now be used exactly
as if they've been recorded and stamped at that new speed, allowing also auto-conformation or other
TimeCode based processes. All information stored in the clips referencing these media in the Timeline
(like fades, sync points, gain curve, ...) are also stretched/squeezed properly. Optionally the media can
be consolidated to convert only the required part
The two processes described above are necessary when a mix of different source material speed have
to be "normalized". In the case where it is known from the beginning that the whole editing and mix will
have to be stretched back to the other (original rushes) speed, Merging provides a very convenient
solution in term of hard-disk space, conversion time and finally sound quality. The Virtual Transport
Video Player allows playing the video editing at a different speed than the audio material allowing
matching (for instance and in the majority of cases) a video running at 24 frames per second with an
audio editing stamped at 25 frames per seconds. This avoids compressing the audio so it matches the
video being played too fast (25fps instead of 24) but preferably run the video at the correct speed
(24fps) and therefore the audio also.
Surround Post-processing
Conversion of a final mix from 24 to 25 for DVD/Video distribution of a film or 25 to 24 for film distribu-
tion of a video shot and edited movie.
Pyramix allows stretching/squeezing a whole surround mix by selecting the menu Project > Surround
Post-processing and choosing the Prosoniq MPEX2 24/25 Time Stretcher module. This function
stretches/squeezes a whole 5.1 mix without inter-channels phase artifacts thanks to the new Prosoniq
MPEX2 algorithm. This function allows processing multiple stem surround mixes stem by stem. Due to
artefacts introduced by most time stretching algorithms available until now, the normal procedure was to
separate the dialogue stem and the music/effects/ambiance stems, time-stretch them separately and
remix them afterward. Although the Surround Post-processing function allows this methodology, this is
no longer required due to the very high quality of the MPEX2 module. Therefore a complete mix can be
stretched in one pass retaining maximum sound quality.