Conforming audio
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Premiere Pro processes each audio channel, including
audio channels in video clips, as 32-bit floating-point data at
the sequence sample rate. This processing assures maximum editing
performance and audio quality. Premiere Pro conforms certain types
of audio to match the 32-bit format and the sequence sample rate.
If conforming is required, it is done when a file is imported into
a project for the first time. Conforming takes some time and disk
space. A progress bar appears at the lower right of the Premiere
Pro window when conforming begins. Premiere Pro saves conformed
audio in CFA audio preview files. You can determine
where to save these audio preview files by specifying a Scratch
Disk location for Audio Previews in the Project Settings dialog
box.
You can work with audio files, even applying effects to them,
before they are fully conformed. However, you can preview only the
parts of the files that have been conformed. You cannot hear unconformed
sections on playback.
These rules determine which types of audio get conformed:
Uncompressed audioPremiere Pro
does not conform audio in uncompressed clips that were recorded
in one of the natively supported sample rates, when you use these clips
in sequences with matching sample rates.
Premiere Pro does conform audio in uncompressed clips when
you use them in sequences with non-matching sample rates. However
no conforming is done until you export the sequences or create audio
preview files.
Premiere Pro does conform audio in uncompressed formats that
were not recorded in a natively supported sample rate. In most of
these cases, it will upsample the audio either to the nearest supported
sample rate, or to a supported sample rate that is an even multiple
of the source audio sample rate. For example, it will upsample an
11024Hz source to 11025Hz, since that is the nearest supported rate,
and there is no supported rate that is an even multiple of 11024.
Compressed audioPremiere Pro
does conform all compressed audio, such as audio found in mp3, WMA,
MPEG, or compressed MOV files. It conforms this audio at the sample rate
of its source file. For example it will conform a 44100Hz mp3 file
at 44100Hz. However, if the conformed audio is used in a sequence
with a non-matching sampling rate, as when a 44100Hz clip is used
in a 44000Hz sequence, the audio will play back at the sample rate
of the sequence without further conforming.
Premiere Pro does not conform a file that was conformed
in one sequence when you import it into another sequence with the
same audio sample rate, so long as you haven’t moved or renamed
the file since it was conformed. Premiere Pro keeps the location
of the conform files for all files it has conformed in the Media Cache
Database.
 To avoid conforming, use audio editing
software, or transcoding software, to convert your files to natively-supported
uncompressed formats at the supported sampling rates. In
addition to conforming some files, Premiere Pro also creates a PEK file
for any file containing audio when it is first imported into a project.
It uses these PEK files for drawing the audio waveforms in Timelines.
Premiere Pro stores PEK files in the location specified for Media
Cache Files through the Media pane of the Preferences dialog box.
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