The GSM audio file format was created for telephone service in Europe, so it is mainly used for telephone quality voice. Compression and decompression are slow, the audio quality is very poor by current standards, but the main problem is that the raw GSM format is not supported by most audio players. If an application can't export voice recordings in a different format, it creates problems for using them in other applications.

1 GSM file compatibility issues

In fact, the GSM format is not as simple as Wikipedia describes it. According to the 6.10 specification, it is an 8 kHz file with a bitrate of 13 kbps. This is only true for raw files with the .gsm extension. Microsoft's GSM codec supports many more sample rates, up to 44100Hz, and the compressed data is stored in a RIFF container with a .wav extension.

There is a curious situation when a GSM file created in Windows cannot be played in telephony software, and a raw GSM file from Linphone cannot be played by Windows media player.

2 Choosing a tool for converting GSM files

There are a few GSM converters out there, but most are for IP telephony and only open one file at a time. Have you ever tried converting several thousand voice recordings at once? If you're looking to convert recordings from Asterisk or a similar system in bulk, you'll need something more advanced.

Audio Converter Plus is a versatile audio file converter program that will help you easily convert GSM files with excellent music quality. As an output format, it allows you to use both lossy and lossless formats of your choice. But much more importantly it can read Microsoft GSM in WAV container and save them in raw GSM format. I.e. it solves the compatibility problem I wrote about above.

3 Convert GSM to WAV step by step

Overall, the conversion process is no different from dozens of other guides that are already on our site.

Step 1. Download GSM To WAV Converter

Download Audio Converter Plus from our site: https://www.abyssmedia.com/downloads/audioconverter.exe

Step 2. Installation

Run the downloaded file audioconverter.exe to start installation, which is fast and requires no knowledge. After installation, double click on the converter icon, you will see the user interface below.

Step 3. Add GSM Files To Conversion List

Add the GSM audio files by using "Add File" or "Add Folder" buttons or simple drop GSM files into the converter.

Step 4. Select the output folder

In the lower right corner of the main program window, you'll see the Output Folder option. Just click the Browse button to set the output path, which is where the converted WAV files will go.

Step 5. Set Output Format

If you need to convert MS-GSM to raw GSM, then choose this codec from the list of output formats. For conversion in the opposite direction, select the WAV format. As for the sampling frequency, leave it the same as the original file. The converter will change it itself if necessary.

Step 6. Start Converting

Click on the "Convert" button, the conversion task will be started immediately. After the process is completed, you will see a flashing converter icon on the taskbar.

4 Conclusion

Frankly, this article might not exist if software developers were more responsible about standards. Creating incompatible implementations of the GSM codec did not benefit anyone. Alas, Microsoft solved the problem in the simplest way and simply stopped supporting the GSM 6.10 codec in Windows Media Foundation. Now using an audio converter has become the only option.

Considering that the patent for using the MP3 codec has already expired, I hope that IP telephony applications will switch to it and forget about the outdated GSM forever.

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