Are all mp3 encoder/decoders equal?

  • Thread starter Thread starter davelivinstone
  • Start date Start date
I have Scmpx and Razor Lame.
Both work fine.

I think if your posting on Nowhere,you don't want to encode higher than 160 anyway.
Waldo would be the one to ask on that.


Pete
 
'The way you decode is fixed'

Incorrect, as there is different encoding algorythms, there is different decoding algorythms. There is accepted standards, but you can get very different results from one codec to another.

W.
 
Nope. There is one and only one algorithm. Howvere, ther are many differen implementations, and several of them have severe bugs. But it's not a question of choosing different ways of doing it, as with encoding, but of bugs. A specific mp3 stream should always result in the same raw bit stream (with the exception of output errors).

See: http://privatewww.essex.ac.uk/~djmrob/mp3decoders/intro.html
for more info and extensive test data on tons of decoders.
 
If every algorythm was the same, there wouldn't be errors in some over others! The CBR/VBR algorythm is completely different, etc.

There is many subsets of encode, which require different algorythms to decode, and some decoders fall back on older algorythms etc.

W.
 
TheRealWaldo said:
If every algorythm was the same, there wouldn't be errors in some over others!
Click to expand...

Yes there would, because as I said, there are errors in the implementation of the algorithm. One algorithm can be *implemented* in different ways. There differences in decoding an mp3 stream is because of errors in the decoding implementation. Not because of differences in the algorithm.


The CBR/VBR algorythm is completely different, etc.
Click to expand...

Yes, just as the algorithm for decoding real audio is completely different from the algorithm for decoding mp3, because the data is stored differently.

There is many subsets of encode, which require different algorythms to decode, and some decoders fall back on older algorythms etc.
Click to expand...

Did you look at the link I posted?
 
CBR and VBR are MP3 types.

BTW, I write codecs ;) You can say that there is one algorithm, but that's a misnomer, has been for years. Used to be only one, now you have version 1 (ISO/IEC 11172-3), version 2 (ISO/IEC 13818-3), version 2.5, etc., you also have layer I, II, and III, CBR and VBR. Each is a seperate algorythm. Now, whilst the 'recommended algorythm' that comes from the creator of the format should be used, it isn't always. The format also varies slightly from encoder to encoder, and doesn't always follow the same rules. Yes, they are also implemented differently, but some are completely modified.

eg. You can use a version 2 decoder to play a 2.5 mp3, but it's not going to sound as good, or decode the same as a 2.5 decoder. The algorythm IS different between those two formats, but they have a few similarities.

Simple fact of the matter, however you choose to describe it, there IS a difference in the output between decoders.

I'm not going to get into a back and fourth war over terminology!

W.
 
Well, nothing you say in this last post actually disagrees with what I have said, except for one minor point, so I guess this means you now agree. :)

You still use 'recommended algorythm' [sic] to mean the standard reference implementation. Specific code is not the same thing as an algorithm. Code is implementation of an algorithm.
 
1.0 and 2.0 have different algorythms altogether however, if you check the ISO specification.

W.
 
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