Where the name mp3 comes from?

[kurbads]

What does it mean "Mpeg Layer 3"?
What are "Layers" 1 & 2?
If it originaly was VCD audio why VCD and DVD use mp2 instead of mp3?
What is relation between mp2 and mp3?
What happened to Mpeg3 format? Why there are only Mpeg1, Mpeg2 and Mpeg4 formats?

[jagabo]

Fraunhofer MPEG compression: MPEG 2, Layer 3

Layers 1 and 2 (MP1, MP2) are higher bitrate variations of MPEG audio compression.

http://www.fraunhofer.de/

[AlanHK]

http://en.wikipedia.org/wiki/MPEG

[Cornucopia]

MPEG1 encoding for audio has 3 "layers" of complexity. The more complex, the more difficult to encode and decode, resulting in extra steps and ultimately more DELAY in the line.

Layer 1 is simplest, lowest delay (can be easily done IN REALTIME on many LOW PC's and chips), meant for realtimer conversion & streaming from old Analog recording studio sound to data packets over ISDN line, then decoded back to Analog at another recording studio. Originally called "Musicam". Still in use sometimes (many more high quality options now).

Layer 2 a little more complex (in terms of subbands, psychoacoustic profile matching etc), a little more delay, meant for most standard MPEG use--VCD, DVD, DVB, HDV audio, etc.

Layer 3 MORE complex and not able to be done in realtime (originally, but now we have such faster computers). More subbands, more dynamic adjustment, etc. Highest efficiency. Called "MP3" for short. Popularized by Napster, et al. Great for music compression on the internet/mobile.

ALL 3 have similar bitrate choices (~64-384kbps) and samplerates (32, 44.1, 48kHz), but the more complex it is, the more efficient (and quality-retaining) it is (at any particular bitrate)

>>>edit: An MPEG1Layer1 file @384kbps ~= MPEG1Layer2 @256kbps ~= MPEG1Layer3 @192kbps.<<<

MPEG2 added lower bitrate choices (~24-64) and samplerates (8, 16, 22.05, 24), but everything else is the same. MPEG2 decoders can decode MPEG1 streams as well as MPEG2 streams (most are MPEG2 decoders, but they are usually encoded as MPEG1 unless those expanded rates are needed).

IIRC, MPEG2.5 added multichannel (5.1, 7.1) capability in Backwards-compatible mode (works by redundant downmixed channels for the stereo decode), or Non-Backwards-compatible "NBC" which was later changed to be called "AAC" (advanced audio compression).
AAC has been improved again in use with MPEG4.

MP3 has NOTHING to do with MPEG3 (which was the HiDef version of MPEG2, which got subsumed/folded into MPEG2 as additional Levels/Profiles).

Scott

[kurbads]

http://en.wikipedia.org/wiki/MPEG

It says: "MPEG-1: Initial video and audio compression standard. Later used as the standard for Video CD, and includes the popular Layer 3 (MP3) audio compression format. "
But in fact you can't add mp3 to VCD! No VCD authoring/encoding program will allow it. It will tell the mp3 audio is not in the right format end dismiss/reencode it. So a lot of widespread misunderstanding here.

Thank you Cornucopia for explanation.

[Cornucopia]

http://en.wikipedia.org/wiki/MPEG

It says: "MPEG-1: Initial video and audio compression standard. Later used as the standard for Video CD, and includes the popular Layer 3 (MP3) audio compression format. "
But in fact you can't add mp3 to VCD! No VCD authoring/encoding program will allow it. It will tell the mp3 audio is not in the right format end dismiss/reencode it. So a lot of widespread misunderstanding here.

Thank you Cornucopia for explanation.

You're wrong. I have successfully made 2 test authored VCD's with MP3 audio. Of course, VCD players (and DVD players that do VCD as well) don't like it. They'll play the video OK, but will have "skippy" audio. It's in there, they just don't know what to do with it. This even from players that understand raw MP3 files. (For the record, I've made a VCD with AC3 audio as well, SAME problem with playback).

You've also mis-read the quote. It's saying the MPEG1 standard includes MP3, not the VCD standard (>>>edit: re--including MP3<<<).

Scott