ExifTool Forum

General => Metadata => Topic started by: linuxline on May 10, 2018, 08:06:28 PM

Title: Emphasis & Duration
Post by: linuxline on May 10, 2018, 08:06:28 PM
Hello,

"Emphasis" refers to what aspect of metadata? This was part of the results from the command line ExifTool for an audio file.

<tr><td>Emphasis</td><td>None</td></tr>

Also, metadata result "Duration" of the audio file did not show the exact length. The result stated a length of time with the word "approx." in commas. Could you describe why this is so, especially when all of the other results are so accurate?

Thank you!

Title: Re: Emphasis & Duration
Post by: StarGeek on May 10, 2018, 09:49:23 PM
According to this page (https://www.mp3-tech.org/programmer/frame_header.html)

"The emphasis indication is here to tell the decoder that the file must be de-emphasized, ie the decoder must 're-equalize' the sound after a Dolby-like noise supression. It is rarely used."


Title: Re: Emphasis & Duration
Post by: Phil Harvey on May 10, 2018, 09:56:28 PM
The length is approximate because it is (most likely) calculated as the file size divided by the bitrate, which doesn't account for the existence of headers or metadata in the file.

- Phil
Title: Re: Emphasis & Duration
Post by: linuxline on May 11, 2018, 06:43:33 AM
Thank you very much again! That all makes sense, especially how you explained.