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Topic: why is AAC called mp4? (Read 7537 times) previous topic - next topic
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why is AAC called mp4?

one silly question: why has AAC also got the mp4 extension? Is it the mp4 format, say the sequel to mp3?

an explanation would be nice  thanks!
FB2K,APE&LAME

why is AAC called mp4?

Reply #1 –
AAC is usually found in an MPEG-4 container; so MP4.

MP3 is MPEG-1 audio's layer 3, so MP3.

MPEG-3 was meant to be for HDTV, but MPEG-2 was found to be adequate, so MPEG-3 was never made, AFAIK.

why is AAC called mp4?

Reply #2 –
MP3 = MPEG 1/2 Layer 3
is an Audio Codec
see http://en.wikipedia.org/wiki/Mp3

MP4 = MPEG 4
contains many media formats (aac is in MPEG-4 Part 3), a media container (MPEG-4 Part 14) and some more stuff. This container may be used to wrap around aac coded audio data. In this case you should use the mp4 extension.
see http://en.wikipedia.org/wiki/MPEG_4

Added some wikipedia links

why is AAC called mp4?

Reply #3 –
There is also MPEG-2 AAC and it's not much different than MPEG-4 AAC.  MP4 is the extension for the standard file format (as defined by MPEG-4 Part 14) that commonly is used to hold AAC.

why is AAC called mp4?

Reply #4 –
MPEG-4 AAC just adds PNS and LTP to MPEG-2 AAC I think.

why is AAC called mp4?

Reply #6 –
Can someone clarify if the difference between MPEG 2 AAC and MPEG 4 AAC is a different codec?

Ie would you need a different codec to encode MPEG 2 AAC than MPEG 4 AAC? I thought the codec was different to the container.....

Thanks!

why is AAC called mp4?

Reply #7 –
Quote from: brock_05 on
Can someone clarify if the difference between MPEG 2 AAC and MPEG 4 AAC is a different codec?

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why is AAC called mp4?

Reply #8 –
the codec is the same. It just contains more tools, like shown in that graphic by eevan.

MPEG-2 AAC used either a RAW stream (no container format), ADTS or ADIF. MPEG-4 AAC uses ADTS, ADIF, or the MP4 container (the latter being the usual.
There's a small difference in the ADTS (or ADIF? or both?) between MPEG-2 and MPEG-4, but that's all.