Hydrogenaudio Forums > difference between MPEG2-AAC and MPEG4-AAC ?

Full Version: difference between MPEG2-AAC and MPEG4-AAC ?

Hydrogenaudio Forums > Lossy Audio Compression > AAC > AAC - Tech

legg

Apr 6 2005, 13:35

AAC is used as the common name for MPEG4-AAC. But there's also MPEG2-AAC.

Is MPEG-4 AAC built on MPEG-2 AAC? or is it a completely new standard?
What are the advantages of each? main differences?

Thanks in advance.

ps. If this has been asked before, excuse me, I did use the search button but found nothing.

Garf

Apr 6 2005, 14:59

MPEG4-AAC == MPEG2-AAC + PNS tool + AAC Long Term Prediction profile (AAC LTP)

For practical use, the availability of the PNS tool is useful for low bitrates. AAC LTP is basically never used.

legg

Apr 7 2005, 08:53

QUOTE(Garf @ Apr 6 2005, 02:59 PM)

MPEG4-AAC == MPEG2-AAC + PNS tool + AAC Long Term Prediction profile (AAC LTP)

For practical use, the availability of the PNS tool is useful for low bitrates. AAC LTP is basically never used.

So it should be safe to say that MPEG-2 AAC and MPEG-4 AAC are equivalent at average and higher bit rates (>128kbps)?

Also, is there a reason as to why AAC LTP basically never used?

Greetings.

Garf

Apr 7 2005, 09:03

More complexity, fairly little gain.

schonenberg

Apr 7 2005, 09:46

Will LTP ever be used?

rjamorim

Apr 7 2005, 10:00

QUOTE(schonenberg @ Apr 7 2005, 12:46 PM)

Will LTP ever be used?

It probably has its niches, but I don't think it will ever be popular. At least, not as popular as LC.

Garf

Apr 7 2005, 10:05

It won't help that HE-AAC's extensions are only specified for LC AAC.

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