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Difference between decoding?, I.E. Real-time versus decoding to .wav
Man-eating cow
post Aug 9 2003, 17:40
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My friend and I are having an argument over mp3s (or really just any kind of lossy encoded audio in general, but I'll use mp3s for sake of conciseness). He claims that the output from an mp3 decoded in real-time in an audio player, like just hitting Play in foobar or whatever, is different from what you would get if you decoded the mp3 to a wav file and then listened to the wav file. I say that it's the same decoder either way, except the real-time decoding just skips the writing the file to disk.

As far as I know, when an mp3 is decoded in real-time, it is just converted to PCM audio and sent to the sound card, whereas when you decode to a wav you just have a PCM wav that is stored on the hard drive, then sent to the sound card. The output should be identical, but he stubbornly refuses to accept that.

Who is right? And if possible, does anyone have any links that show proof? (He's not likely to believe me otherwise, he'll just say "Oh that's just some forum, who knows what they think smile.gif )

(I can clarify either of our positions if needed)
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AtaqueEG
post Aug 9 2003, 18:31
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There could be differences. For example, Foobar has the option to dither the sound output or not, and it could make a difference.

You know, with two people, blind testing is really easy. Do this: load the same song (agree on songs you know) in Foobar compressed and decompressed in player of choice. One of you listens (with headphones and NOT looking at computer monitor) while the other plays either one of the two files, WITHOUT telling the other one which one. Repeat 15-20 times. Tell the one who listens to write down which file did he think was playing each time. If the listening guy could tell the correct file playing in more than 95% of the cases, then he CAN hear a difference, which means, of course, that THERE IS A DIFFERENCE. If not, well, you win your argument.

I have a feeling though, that you will.

Oh! Something else: THE SETTINGS FOR BOTH DECODING AND PLAYING MUST BE THE SAME

Have fun


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sld
post Aug 9 2003, 18:33
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There may be inaudible differences that may be basically un-ABXable.
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AtaqueEG
post Aug 9 2003, 18:39
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QUOTE (sld @ Aug 9 2003, 11:33 AM)
There may be inaudible differences that may be basically un-ABXable.

Inaudible, un-ABXable differences are irrelevant.
In fact, such "differences" might not even exist, you know


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I'm the one in the picture, sitting on a giant cabbage in Mexico, circa 1978.
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AstralStorm
post Aug 9 2003, 21:59
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This is slightly old, but still useful:
http://mp3decoders.mp3-tech.org

This post has been edited by AstralStorm: Aug 9 2003, 21:59


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