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Compressing your audio to Mp3 for an AVI file

This method is very simple and involves importing your wav audio to virtualdub and selecting Lame MP3 compression settings. (You may need to download the AMVapp for the LAME ACM MP3 codec)

Setup Options

You should ideally add your audio either during the 2nd pass of your DivX/XviD encode or by muxing it after. To mux the audio after you have encoded the video, load your encoded video into Virtualdub and in the Video menu choose "direct stream copy".

To compress your audio in Virtualdub, go to the Audio menu and choose "Audio from other file..." and you will be able to load your WAV file.

Then, choose Full processing mode in the Audio menu, and then finally choose Compression from the Audio menu.

A new window will appear with a list of possible audio compressors, you will want to choose Lame MP3. DO NOT choose the entry called MPEG Layer-3 as that is inferior to the Lame compressor.

Once selected, in the box on the right, a long list of settings will appear. The first thing you should ask yourself is what is the "sample frequency of my audio and is it in stereo?". CDs are always 44.1KHz, dvds are 48KHz. There is a problem that lots of people seem to have in Virtualdub with "Audio Compression not possible" errors. So please read this carefully:

Virtualdub cannot encode something at 44.1kHz Stereo if the source is 48kHz or mono etc. The reason you are getting the error is because you are encoding the stream without converting the input to match the selected compression type. So, make sure that you select the right options for your input audio - if you have a 48kHz stream then choose that as the encoding option.

In the Lame compression box you will see a list like this:

44100 Hz, 320 kbps CBR, Stereo 40KB/s
44100 Hz, 256 kbps CBR, Stereo 32KB/s
44100 Hz, 224 kbps CBR, Stereo 28KB/s
44100 Hz, 192 kbps CBR, Stereo 24KB/s
44100 Hz, 160 kbps ABR, Stereo 20KB/s
44100 Hz, 160 kbps CBR, Stereo 20KB/s
...
44100 Hz, 128 kbps CBR, Stereo 16KB/s
44100 Hz, 124 kbps ABR, Stereo 16KB/s

These mean as follows: 44.1KHz audio at 320kbits per second, Constant BitRate, Stereo. The eagle-eyed amongst you will notice that there are ABR (Average BitRate) options.

In the previous guide ABR was recommended but it has come to my attention that files encoded with ABR are not as stable as I once thought. So, I recommend choosing a CBR option. As for the bitrate 160kbps is fine but anything 128 or higher will be "ok". If you can do 192 or higher then that would be even better but it depends on how much space you want to spend on your audio encode. Something close to CD quality would be 224 kbps or above.

When you've set everything up, return to the main vdub window, go to the File menu and choose "Save as Avi" and you're done.