MPEG1 and MPEG2 audio are compatible, which implies that an MPEG2 audio
decoder can handle MPEG1 bit streams, and that an MPEG1 decoder can play
back a compatible stereo downmix whenever an MPEG2 multichannel audio stream
This does not imply that MPEG1 and MPEG2 audio are the same.
MPEG1 audio has three *layers* (NOT *levels*). It describes single or
two-channel coding at sample rates of 32, 44.1 and 48 kHz. Bit rates go from
32kb/s up to 448kb/s.
MPEG2 audio has three layers as well, and it provides two extensions to
1) Low sample rates: it describes single and two-channel coding at sample
rates 16, 22.05 and 24 kHz. Bit rates go from 8kb/s to 160kb/s
2) Multi channel: it describes a system that can handle up to 5.1 channels.
Sample rates are 32, 44.1 and 48 kHz.
If you plan to make a decoder that can handle two-channel signals using the
regular sample rates, you can do with ISO/IEC 11172-3.
If you plan to cover low sample rates and/or multichannel, you need both
11172 and ISO/IEC 13818-3.
>>> >I have seen the FAQ already. But i am still confused. Just tell me does
>>> >MPEG1 and MPEG2 have separate mp3 layers or the audio standard is
>>> >common. I am working on an mp3 decoder and i want to know what type of
>>> >sourced generate mp3.
>>> Both have the same MPEG audio.
>>> So MPEG audio level-3 (MP3) is common for MPEG1 and MPEG2.
>>They are not the same... MPEG-1 (layer 3) is only 1 or 2 channel and
>>44.1kHz, or 48 kHz. MPEG-2 support 5 channels, (secondary language
>>changes), 16kHz, 22.05 kHz, and 24 kHz. I don't have the standards in
>>front of me, so there may be additional differences between the two.
>Still I believe my words are valid. If you look at
>you can see a detailed description about this matter like:
>"Do I have to use MPEG-1 Audio with MPEG-1 Video and MPEG-2 Audio with
>No, due to the compatibility, MPEG-2 Audio can be used with MPEG-1 Video as
>well. The other way around, MPEG-1 Audio can be used with MPEG-2 Video
>without any restrictions. Any combinations of MPEG-1 and MPEG-2 Audio and
>Video can be handled by the system as specified by the MPEG-Systems
>ISO/IEC 11172-1 for MPEG-1 and ISO/IEC 13818-3 for MPEG-2. "
>So you are allowed to use all audio profiles with both videostandards. Not
>all suppliers have done this. And using the most sofisticated audio with
>MPEG1 does not make much sense.