MP1 and MP2 Specification Options

[filoe]

I am searching for a detailed MP1 and MP2 specification to write a decoder for both. And by the way if someone has a big and detailed aac(+) specification i could also need it.
So if someone has a good documenation or specification of these codecs i would be very thankful

[filoe]

Oh and another question. Am I allowed to create a mp1/2 decoder and publish it as freeware?
Or do I have to pay first.

[Snowman]

I am searching for a detailed MP1 and MP2 specification to write a decoder for both. And by the way if someone has a big and detailed aac(+) specification i could also need it.
So if someone has a good documenation or specification of these codecs i would be very thankful

The spec for MPEG-1 Audio Layer 1/2 is available at ISO/IEC http://www.iso.org/iso/home/store.htm (if I'm not mistaken it's ISO/IEC 11172-3), but you have to pay for it. There you can also get the spec for MPEG-4 HE-AAC (aka AACplus), this one is ISO/IEC 14496-3 (there is also an MPEG-2 flavor of (HE-)AAC defined in 13818-7, which is basically a subset of MPEG-4 HE-AAC).

At the ISO store, you can also get reference implementations as source code, which might not be computational optimal or in a software-engineering too nice shape, but work as intended.

[Porcus]

Am I allowed to create a mp1/2 decoder and publish it as freeware?

I am not a lawyer, but ffmpeg decodes both MP1 and MP2 and is available under (L)GPL. ffmpeg also encodes MP2.

[maikmerten]

Am I allowed to create a mp1/2 decoder and publish it as freeware?

I am not a lawyer, but ffmpeg decodes both MP1 and MP2 and is available under (L)GPL. ffmpeg also encodes MP2.

ffmpeg obviously also implements codecs with licensing terms that do not allow distribution without licensing fees. However, in case of MP2 it appears that all patents *may* have expired by now http://en.wikipedia.org/wiki/MPEG-1#Patents