Encode AC3
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Encoding AC3 from lossless TrueHD or DTS-HD.MA audio tracks
- Demux audio.w64 file with eac3to applying -down6 to mix the surround channels for the 7.1 tracks if it's the case.
- Open in Sound Forge the audio.w64 file that you just created with eac3to and highlight the center channel wich usually is the third stream, which has primarily dialogue (no music or other sound effects).
- Process -> Normalize. Check the Average RMS level (loudness) and then press Scan Levels. When the scan is done, a value for the RMS should be show (remember that value, or write that somewhere in a .txt). Now you need to press Cancel and not Ok, otherwise Sound Force will normalize the audio.
- File -> Save As. Make sure "Dolby Digital AC-3 Pro" is selected, also the "5.1 Surround DVD".
Click "Custom" button and make sure the settings from the Tab Audio Service match with the picture from below which is that we use for HD encodes Then set the Dialog normalization to the RMS value you wrote down earlier or you remeber it (-22 dB in the dialog for this case.)
- On the Preprocessing tab Uncheck all input filtering and surround channel processing. Make sure that RF overmodulation protection is unchecked. For the Line mode profile, the recommended value is "Film: Light", aswell none being good also.
- Finally, press OK and then Save the .ac3 file to the folder of your choice and wait the audio being encoded.
- The resulting file will be your final main audio to be used later on down the line in muxing.