Introduction
This guide illustrates the process of conversion of .ac3 audio file in the .waw or .mp3 format thanks to the open source mAC3dec software.

mAC3dec may be downloaded from the Software MAC page, where you may also find useful information on the installation of the software and the link to the official site.

Details for use are as follows:

Open the program by clicking twice on mAC3dec file. Click on "Add AC-3..." voice of the menu "File" to open the .ac3 file that you want to convert.

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Now you must chose in what type of format you want to convert the .ac3 file. The choice illustrated in the picture is between .WAV (non-compressed format) and .MP3 (the well-known audio compression format). Then select one of these two formats from the list "Format".

Remember that the .wav file may weigh more than the .ac3 file that we had at the beginning (even more than four times), while the size of the .mp3 file would result about 1/3 of the .ac3 file.

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Click on "Custom" voice i n the "Sample Rate" list .

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The configuration window will now appear according to the chosen format : see on the right the configuration window of WAV format. Then set up as illustrated in the picture:

Compressor: None

Rate: 48.000 (DVD derived audio)

Size: 16 bit

Use: Stereo

Click on "OK" button to close the window.

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By selecting MP3 format, the "MP3 Options" button will appear below. Click this button, to enter the configuration window of the MP3 format as illustrated in the picture below.

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In the "mp3 options" windows set up as below:

Channels: Stereo

Quality: High

Sampling Rate: 48.000 kHz

Method: CBR

Bitrate: the value of the bitrate determines the quality of sound and the size of the .mp3 file obtained with the codification. The higher the bitrate, the better the quality, and the heavier the file will be too. So you must choose the bitrate according to your requirements. The minimal value for an acceptable quality can be fixed at 128 while 160 and 192 are medium values that are often used.

Click on "OK" button to close the window.

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Check some important options of the program by means of the "Preferences" voice of the "mAC3dec" menu:

If you select the "Same Destination as Input" box, the converted file may be saved in the same folder where the .ac3 file is.

Select the "Disable Progress Bar" box to disable the progress bar during the codification process in order to make the operation faster.

Then check that the "Dolby Downmixing" option is flagged.

Click on "OK" button to close the window.

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To start the conversion process, click on "Start" button. Then check that the "Normalize" box is flagged.

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During the process, the program shows you information about time elapsed, the percentage of progress and the size of the created file. It is possible to interrupt the operations at any time by clicking on "Cancel" button.

At the end of the process, you will obtain the file in .wav or .mp3 format, ready to be heard.

To put this file together with the video file (.m2v file extracted by DVD together with .ac3 file with OSEx and converted for example in .mov-3ivx format with DIVA), you must join both video and audio flows by means of QuickTime Pro software (purchasable from Apple) or any compatible software for video editing.