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SusannNutter
Known Participant
November 23, 2015
Question

Change audio sample rate

  • November 23, 2015
  • 1 reply
  • 2549 views

Captivate 8

In the attempt to lessen the size of my Captivate files, it's been suggested to change the sample rate of the audio files. Currently at 44100, is it possible to change it to 22050 (near FM)?

I read something from Rod Ward suggesting to record at a high quality and then set the audio quality for the published output a lower one - no lower than 64kbps, However, when I did this (at 1 channel, 44100, 128 CD quality, FM bitrate 64) there was no significant reduction.

SO - what's the best way to reduce auido size for a project?

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1 reply

RodWard
Community Expert
RodWardCommunity Expert
Community Expert
November 24, 2015

HI there Susan.

Are you talking about reducing the size of your CPTX project file or reducing the size of the published output?  You don't really need to reduce the size of the CPTX.  It's better to have the original audio files in the project file as high quality uncompressed WAV files.  When Captivate publishes out, it converts these WAV files to compressed MP3 at whatever reduction in quality you specify. 

There are two different things in play here:

The audio sampling rate is number of samples per second that are used to digitize a particular sound. Higher rates produce better results.

Bitrate, measured in kilobits per second or kbps for short, describes the rate at which bits are transferred from one location to another. In other words, it measures how much data is transmitted in a given amount of time. In the audio world, bitrate is used as a measurement of the quality of an audio file.  The higher the bitrate, the more data is being used to define the audio clip, meaning it will more accurately reproduce the original sound.

For my own Captivate courses, where I do my own voiceover work, I prefer to record audio at a sample rate of 44100 or 48000.  I don't find l get sufficient data for good clear audio at a sample rate of 22050.

As mentioned in my e-books about Troubleshooting Adobe Captivate, you can usually get away with setting the published output quality to around 64 kbps without noticeable loss in clarity.  This SHOULD significantly reduce the output project file size.

So record and store your audio at HIGH quality settings, but work out what you can tolerate for the output bitrate and set Captivate to publish to that.

    S
    SusannNutterAuthor
    Known Participant
    November 24, 2015

    Thanks much, Rod!

    I get it that recording my voiceovers at 44100 will be fine. But I'm still confused as to where to indicate published output quality to 64 kbps. When I chose Audio > Settings and indicated FM Bitrate,(64kbps), I got no significant reduction in output project file size. Is there another place for me to choose published output quality?

    This seems to be the right path - I apparently don't know where to make the 64kbps selection.

    SMILES,

    Susann

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