AcmStreamNotPossible when using Naudio library on Windows Server 2008 RC2 (on Amazon EC2)

Question

Similar but different to: Firstly

NAudio error: "NoDriver calling acmFormatSuggest"

and now

ACM Stream Convert exception displaying AcmNotPossible

I'm having similar problems trying to get NAudio to work on an Amazon EC2 instance that has "no sound card"

I got the ACM codec from here: http://www.rarewares.org/mp3-lame-dshow-acm.php

However now I get a different error message:

"AcmNotPossible" which i'm trying to work out how to solve...

I've tried installed Virtual Sound Card on the EC2 instance but that has not helped... The instance is running Windows Server 2008

I've been reading about ACM on wikipedia: Audio Compression Manager (ACM) is a Windows multimedia framework that manages audio codecs (compressor/decompressors). ACM can also be considered an API specification. A codec must conform to the implicit ACM specification to work with Windows Multimedia. http://en.wikipedia.org/wiki/Windows_legacy_audio_components

Anyone got any ideas?

Answer 1

It is nothing to do with whether the machine has a soundcard, but what ACM codecs are installed. You may have installed an ACM codec on the machine, but you must pass exactly the right WaveFormat to it for it to recognise the incoming audio as something it can handle. The Mp3WaveFormat NAudio creates is one recognised by the Fraunhoffer ACM that ships with many versions of Windows.

You can use the NAudioDemo program to query the machine for installed ACM codecs. Each ACM codec can enumerate the input formats it supports (NAudioDemo also does this). I then look at the binary values in a debugger, and make a WaveFormat derived class that exactly matches the supported WaveFormat reported by the ACM codec.