What is ACM driver?

Audio Compression Manager (ACM) is the Windows multimedia framework that manages audio codecs. Codec is a computer program that compresses/decompresses digital audio data according to a given audio file format or streaming audio format.
ACM driver is dynamic-link library (DLL) which contains audio codecs for different audio formats.
ACM drivers can be recognized by their filename extension ".acm". For more details please see Audio_Compression_Manager

The code below can be used to list ACM codecs installed on your computer and see audio formats for specified codec.

        private void WhatIsAcmDriver()

        {

            foreach (DriverDetails dd in AudioCompressionManager.GetDriverList())

            {

                Console.WriteLine("# # #");

                Console.WriteLine("Driver: {0}", dd.LongName);

                foreach (FormatTagDetails ftd in AudioCompressionManager.GetFormatTagList(dd.Driver))

                {

                    Console.WriteLine("FormatTag: {0}", ftd.FormatTagName);

                    foreach (FormatDetails fd in AudioCompressionManager.GetFormatList(ftd.FormatTag, dd.Driver))

                    {

                        Console.WriteLine("Format: {0}", fd.FormatName);

                    }

                }

            }

        }

Output for "Microsoft GSM 6.10 Audio CODEC" (for example) driver see below
# # #
Driver: Microsoft GSM 6.10 Audio CODEC
FormatTag: GSM 6.10
Format: 8,000 kHz; Mono
Format: 11,025 kHz; Mono
Format: 22,050 kHz; Mono
Format: 44,100 kHz; Mono
FormatTag: PCM
Format: 8,000 kHz; 8 Bit; Mono
Format: 8,000 kHz; 16 Bit; Mono
Format: 11,025 kHz; 8 Bit; Mono
Format: 11,025 kHz; 16 Bit; Mono
Format: 22,050 kHz; 8 Bit; Mono
Format: 22,050 kHz; 16 Bit; Mono
Format: 44,100 kHz; 8 Bit; Mono
Format: 44,100 kHz; 16 Bit; Mono
# # #

Audio Library needed for this example is here(Alvas.Audio Free Trial).