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  1. Member
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    Feb 2003
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    Waltham, USA
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    Hi, I have a question regarding audio types. I understand that a wav file is just uncompressed audio and that mp2 and mp3 are compressed versions. However, I don't understand what ac3 files are. I also don't understand how I can convert sound from a simple wav file into 5.1? (which i'm assuming is dolby surround sound). Where or how is that information encoded? I guess i'm just lost on the theory part and don't understand the encoding aspects.

    thanks

    Nick
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  2. I'm not an audio expert (more into video). But here's the little that I do (sort of) know:

    wav - PCM uncompressed audio (there are other uncompressed audio formats out there, but wav is the 'PC standard'). PCM audio is supported by the DVD standard, but you really do not want to use it as the files are HUGE! eg. 3MB ac3 -> 115MB wav, that's wasted space that could be used for a higher bitrate on your video

    MP2 - mpeg1 layer 2 audio. This is the standard for VCD, CVD, and SVCD.

    MP3 - MPEG1 layer 3 (or MPEG2 layer 3). This is really only a format for PC's (and mp3 players).

    AC3 - compressed audio used on DVDs. AC3 is called 5.1 (do a google search I don't want to get into why) and contains 5 digitally encoded channels. Unlike dobly surround there is no bleeding between the channels.

    You can't take a 2channel wav -> 5 channel ac3. But you can take 5 (or 6 again dont' ask) wavs and generate a 5 channel ac3 file.
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  3. Member
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    Apr 2002
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    The State of Frustration
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    Click here for a guide to convert wave to AC3.
    Hello.
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  4. Member
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    Feb 2003
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    Waltham, USA
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    Thanks...so when people are using an avi file (divx, xvid or others) with just a simple audio, I can assume that the audio is now simply 2 channel audio and all the other channels have been lost. Therefore, trying to go back into 6 channels is not the same?
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  5. Member
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    Jun 2003
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    Montreal, Canada
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    Just a clarification. AC-3 is an encoding format, but you can mix 5.1 channels and encode it in AC-3, mix just 2 channels and encode it in AC-3 (a lot of french soundtracks or editor's comments are like that on DVDs), and I even recently came across a 1 channel AC-3 on a DVD (don't remember which)
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  6. I see plenty of guides on how to convert WAV to AC3 and AC3 to WAV. But my question is how do you convert mp2 to mp3? Any guides?

    Thanks Boxingjunkie
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  7. Never mind I think I found my own answer.

    Boxingjunkie
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  8. AC-3 is not limited to 5.1 channels. AC-3 is Dolby Digital, whether it be 1.0 (mono), 2.0 (stereo or matrixed Dolby surround, aka digital version of Dolby Pro-Logic), 4.0, 5.0, 5.1, and 6.1 (also called DD-EX and THX-EX).

    And 5.1 contains SIX digitally encoded signals, don't forget the LFE channel.

    A good example of AC-3 mono are the earlier versions of Stanley Kubrick dvd's.
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  9. Originally Posted by BOXINGJUNKIE
    I see plenty of guides on how to convert WAV to AC3 and AC3 to WAV. But my question is how do you convert mp2 to mp3? Any guides?
    I like to use CDex or RazorLame graphical utilities to make MP3 files from WAV, MP3 and MP2. The LAME MP3 encoder is used in both. Either of those programs can open a MP2 (layer 2) file and create a MP3 (layer 3) file. You need to also download the "lame" command-line utility for RazorLame to work right.


    RazorLame download
    http://www.dors.de/razorlame/download.php

    lame.exe download (for Windows)
    http://www.hot.ee/smpman/mp3/lame393.zip

    CDex download
    http://cdexos.sourceforge.net/downloads.php

    Audio conversion guide is here:
    http://www.doom9.org/audio-guides.htm

    LAME binaries for Linux/UNIX
    http://www.idiap.ch/~sanders/not_lame
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  10. While on the subject.

    I've captured DV to AVi stripped out the WAV with VirtualDub.

    Wav to mp2 (224) gives a smaller file than WAV to AC3(384). This leaves more room for bites to used for the video. Not a lot... but still, the more the better.

    The final format for me will be DVD. MP2 is not really DVD formate yet, it plays fine on my Standalone.

    Am I just looking for trouble by not using AC3?

    I've tried both, I don't hear a difference.
    Don't give in to DVD2ONE, that leads to the dark side.
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  11. WAV can also be compressed as well as uncompessed, the same as AVI can be compressed or uncompressed.
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