VirtualDub help - Dialogs: Audio compression
Processing: Main UI Editing Filtering Rendering/saving Artifacts The pipeline Direct mode Display panes Frameserver Video filter reference Video shader reference Video capture Hardware setup Driver selection Audio setup Pipeline Filtering Info panel Multi-segment mode Timing dialog Performance Troubleshooting Dialogs: Video filters Video frame rate control Video color depth Video range Video compression Audio filters Audio interleaving Audio compression Audio conversion Audio volume Capture settings Preferences On a crash... | VirtualDub can use audio codecs installed in Windows to compress video.
Note | Audio codecs are external drivers created by third parties and are not part of VirtualDub. VirtualDub does not install codecs by itself and does not provide any audio compression technology of its own.
  Selecting a audio codec Currently installed audio codecs are listed on the left. Select No compression (PCM) to disable audio compression, or choose a codec. Once a codec is chosen, the available compression formats produced by the codec are shown on the right. By default, VirtualDub only displays those formats that can be produced by the codec from the current audio source and filtering settings. Uncheck show all formats to display all formats allowed by the codec, but note that attempting a conversion unsupported by the codec will generally result in an error.
  Note | Not all codecs are usable -- sometimes programs install versions of a codec designed only to decompress audio, not to compress it. Also, sometimes the codecs are keyed to a particular program due to licensing concerns, and thus won't work in VirtualDub. In particular, codecs installed by some versions of Windows Media are not licensed for general use and won't work except for in an ASF file under Windows Media Player.
  Note | Installing two codecs that compress and decompress the same format may confuse VirtualDub. This includes having more than one MP3 codec, or having both Windows Media Audio and "DivX Audio" installed.
  Note | There are four common versions of the MPEG Layer-3 codec that appear the same, except for the compression formats supported: `L3CODECX.ACM` - no compression supported `L3CODECA.ACM` (Advanced) - up to 56Kbps `L3CODECP.ACM` (Professional) - up to 128Kbps `L3CODECP.ACM` (Radium warez version) - up to 256Kbps All four of these codecs are very similar and have the same ID in the Windows Audio Compression Manager, so two programs that come with different versions sometimes overwrite each others' codecs when installing. If you used to have certain MP3 compression options and no longer have them, it's possible a program you recently installed has done this.