(Japanese)

Compressing audio data in PowerPoint slide files

The bitrate of audio files recorded with PowerPoint seems too large for “speech”. This tool tries to shrink the file size of pptx/ppsx files by making lower the bitrate of internal audio data (e.g., inserted by Insert > Audio > Record Audio).

• Compress internal m4a audio files to 64kbps bitrate.
• Does not compress images or videos.

Installation

1. Create a main folder (for example, lecrec-tools), a subfolder ppt-in, and download the following script to the main folder (use right-click > Save Link As…).
   • Windows: compress_pptaudio-win.bat
   • macOS/Linux: compress_pptaudio-mac.sh
   • For a simpler step, you can download the archive of this project, and extract the zip file.
2. Download ffmpeg from this site (zeranoe), and extract the zip file.
   • Version: Select release build (4.2.3 on 2020.5.26)
   • Architecture: Select your OS
   • Linking: Static
   • You can also download from ffmpeg original site
3. Copy ffmpeg.exe (or ffmpeg for macOS) from the extracted folder to the main folder created (or extracted) in step 1.

If you already have ffmpeg installed, you can skip step 2 and 3. If have not set the environment variable (path) for ffmpeg yet, you can edit the script (the line with PATH) or simply follow step 3 (copy the ffmpeg executable file).

Usage

1. Put pptx and/or ppsx files under the ppt-in folder. (Backup the files, just in case.)
2. Run the script file (See also Note).
   • Windows: double click compress_pptaudio-win.bat
   • macOS (Linux, Windowsのbash): run compress_pptaudio-mac.sh from terminal
3. Output compressed files can be found in the ppt-out folder.

Note

Windows

• If you are using Windows 10, you will see a warning message for the first time. Click “More info” and then select “Run anyway”.
• Wait until the opened (black) window is automatically closed.
• Do not run the script again before the window is closed.

macOS (Linux, Windows bash)

1. Open bash (terminal). If you use macOS, type “terminal” from Launchpad or Spotlight search.
2. Change the current folder by typing the following command.

    $ cd /Users/<user name>/Documents/lecrec-tools-master
   

   (Press return after you typed. <user name> should be replaced by your user name of the PC.)

3. Run the script by typing one of the following two commands.

    $ chmod 755 compress_pptaudio-mac.sh
    $ ./compress_pptaudio-mac.sh
   

   (chmod is required only once after the download)

Else

• This script converts internal m4a audiofiles to bitrate 64kbps. If you prefer to use other bitrate, change BITRATE inside the script.
• If you use other audio formats, edit the lines that contain m4a inside the script.