Sooner or later you will come to a strange audio format
that you cannot convert to wave. But usually if you can play the audio
you can convert it with Winamp.
DVD audio specifications state that the audio soundtrack
can come in three varieties:
1. Dolby Digital (formerly AC-3)
2. MPEG-2
3. PCM Wave
PCM is lovely to get because it is the computers preferred
audio format and this makes it easy to copy, just use direct stream
copy and your done. AC3 is the best audio format at the moment although
it is soon to be replaced by AAC audio (Advanced Audio Coding) which
is like a high quality MP3 version of AC3 audio. AAC used to be called
NBC (Non-Backward-Compatible), because it was not compatible with the
MPEG-1 audio formats. AAC and AC-3 use similar methods of compression
but AAC uses a filterbank with a finer frequency resolution giving a
much better compression and playback quality.
Anyway, sometimes you get a movie that uses a MPEG-2 (Mp2)
audio track instead of AC3. This presents a problem because neither
Flask Mpeg nor Ac3dec are able to decode Mp2 audio. So here are a couple
of things you can do:
If you are using Fask Mpeg, use the "Direct stream Copy"
option. This will extract the Mp2 audio at the same time your video
converts and should keep them in time.
Open your Mp2 file in Winamp. Everyone knows how to use
Winamp and its free of course ;^). Right-Click and choose
Options > Preferences...
Choose the Audio I/O tab. Now instead of the normal OUT_WAVE.DLL
option, choose OUT_DISK.DLL. Press 'Apply' and Winamp will ask where
you wish to save the file. Choose a location and wait until the audio
is converted into a huge one and a half Gigabyte wave file.
Now open your video file and wave file in VirtualDub (as
explained in the Mpeg2avi tutorial) and convert the wave to MP3 or WMA
audio.
If you don't use Flask Mpeg
If you don't extract the audio with Flask Mpeg, you can
probably use Vstrip, Vobsnoopy, GraphEdit or the TMPGEnc's Demultiplexer
to extract the Mp2 audio. Then you can convert it to Wave with
Winamp as already explained. The usage of all these programs are
explained in my other guides.
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