Check MP3 gain volume level of all phrases in OBI 3.9



before using OBI to produce our DTB, we used to check/balance/increase/decrease the volume level of all the audio files MP3 of a
given book with an external tool named MP3 Gain. We are now moving from Plextalk to OBI. Using MP3Gain, we used to adjust the
volume level to 88db (for instance) for all our MP3 files in one shoot.

1) How is this done in OBI ? I mean how can I be sure that all the recorded MP3 are of a given level (88db) ? I know there is the DB Vu-mtres view , but this is just the display of the level of one phrase after one phrase. This Vu-Mtres view is scaled in - 30 , - 24 , - 18 and so on up to 0. What are these units (-30, -24...) ? I mean how can I compare this level to dbs ?

2) In OBI 3.9 in Tools, there is a way to 'process the audio' (Traitement audio in french) to increase or normalize or update the voice by a factor
of 1 or 1.1 or 1.2 etc...fine. But this is a 'relative' adjustement. What we are looking for if for all books we process and amongst all of them
we need to be sure the audio files are all set around 88db, so that our listeners do not have to worry of the volume level of the chapters of
their books.

Thanks for your help

Hi Eric,

Obi provides basic audio processing functionality. If you want to use advance audio processing, then you can use output of Obi in professional audio processing tools, just as you were doing earlier.

You can apply audio processing to complete project by exporting the project to DAISY format, applying audio processing to all files with external tool and importing the DAISY project back into Obi.

If you want to apply audio processing on a specific phrase or a section then you can use "export or replace audio" menu from the context menu of the Content View. It provides commands to export the audio of phrase/section, on which you can apply audio processing with external software and then import it back at the same place in the Obi project. These commands take care of the phrase timings by itself while import.

There is one caution, please ensure that the audio processing done by external software does not resample the audio files .e. avoid processes like increasing/decreasing speech rate etc. these processes change the length and time of the audio files which may spoil smil timings.

With regards

Thanks Rachana. It is clear. I think we will continue to use our external audio processing tool to insure all audio recordings are at the same volume level.

Any idea what are the units in the OBI vu-meter display ? (-30, -24, -18...0) ? Is there a relation with decibels ?


Hello again,

Yes, they are in decibels.