Merging and Measuring Loudness Levels of 5.1 WAV Stems with FFmpeg

Merging and Measuring Loudness Levels of 5.1 WAV Stems using FFmpeg

In the world of audio production, it is often necessary to merge multiple audio stems into a single file for various purposes such as distribution, archiving or further processing. This article will focus on merging six mono WAV stems (L, R, C, LFE, Ls, Rs) that are part of a 5.1 mix and measuring the loudness levels of the resulting merged file.

Merging WAV Stems using FFmpeg

FFmpeg is a powerful, open-source tool that can be used for a variety of audio and video processing tasks. To merge multiple WAV stems into a single file, you can use the following command:

In this command, -i is used to specify the input files, and -filter\_complex is used to define the filter graph that will be applied to the inputs. In this case, the concat filter is used to merge the six input audio streams into a single output stream.

Measuring Loudness Levels using FFmpeg

Once the WAV stems have been merged, it is important to measure the loudness levels of the resulting file to ensure compliance with various industry standards such as the EBU R128 or the ATSC A/85. FFmpeg can also be used to measure the loudness levels of an audio file using the ebu\_loudness filter.

In this command, the ebu\_loudness filter is used to measure the integrated loudness (I), loudness range (LRA) and short-term loudness (SL) of the merged.wav file. The filter outputs the results to the console, but you can also specify an output file using the -f option.

Key Concepts

• WAV stems: separate audio files that contain different audio channels of a 5.1 surround sound mix.

• FFmpeg: an open-source multimedia framework that can be used for a variety of audio and video processing tasks.

• Loudness levels: a measure of the perceived volume of an audio signal, expressed in LUFS (Loudness Units Full Scale).

• EBU R128: a recommendation from the European Broadcasting Union that specifies loudness normalization for audio and audio-visual content.

• ATSC A/85: a standard from the Advanced Television Systems Committee that specifies loudness normalization for television broadcasting in the United States.

In this article, we have covered the basics of merging multiple WAV stems into a single file using FFmpeg and measuring the loudness levels of the resulting merged file. By following these steps, you can ensure that your 5.1 surround sound mix meets various industry standards for loudness normalization.

References

• FFmpeg website
• EBU R128 recommendation
• ATSC A/85 standard