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I have an m4a audio file and would like to identify the settings that were used to create the recording and determine the resulting file size. Is there a command or program that will display the settings?

The existing file, when loaded into Audacity, shows "Mono, 32000Hz, 32-bit float"; however, when I use these settings to export an equivalent audio file, the file size is almost double. It would appear that I am missing a critical setting(s)!

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Try ffprobe <filename> on each file. Compare the results.

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  • I am not familiar with this software, but don't I need a few more parameters? ffprobe -v error -show_format -show_streams Audio.m4a seems to list a bunch of settings for the file Audio.mp4 My understanding is that bit rate (bit_rate=54439) is important in determining the file size of an exported recording.
    – CentaurusA
    Sep 11 '20 at 2:24
  • Thank you for pointing me to ffprobe. As indicated in my earlier comment, I think the command needs some additional parameters (according to another web post I located). But, I got enough information to help me reduce the file size to about the right order of magnitude.
    – CentaurusA
    Sep 11 '20 at 13:21
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Media information tools such as ffprobe will provide information on the nature of the media, which may include format, encoder used, bitrate, duration, sampling frequency, etc. However, it will never show you the "settings". Simply because "settings" are defined by the encoder, and can be different between different implementations of the same encoding.

Thus, writing out the file to a file with comparable length may require a little experimentation with the compression settings of the codec you use to export the file. If the size is double, you will need to increase compression settings until the resulting file size matches your expectations. When increasing compression settings, audio quality decreases. So check whether the quality of the resulting file is acceptable for your goals.

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  • I was hoping to avoid such a trial-and-error solution by finding out how an existing file had been created and using the same "settings" to export a new recording. Your information indicates that this isn't possible. That is unfortunate, but using the ffprobe switches that I found in another post did give me the bitrate which, when combined, with the base settings in Audacity, did produce an acceptable file size. It appears that this is the best I can expect. So, thank you for your insights.
    – CentaurusA
    Sep 11 '20 at 13:18

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