[CELT-dev] One question about comparison between HE-AAC v2 and CELT

Alex Converse alex.converse at gmail.com
Thu Aug 5 08:34:15 PDT 2010

On Thu, Aug 5, 2010 at 11:01 AM, wei <tsingmei at gmail.com> wrote:
> But Cisco adopts HE-AAC in it's telepresence product which is the dominant
> HD video conference product. They use hardware to decrease the delay?

You may be confusing AAC-ELD with eAAC:

To quote 14496-3 suppart 1: "The enhanced low delay AAC object type
(ER AAC ELD) is identical to the ER AAC LD object type, plus the
utilization of a Low Delay Filterbank (LDFB) and an enhanced low delay
window. It also permits combinations with the PNS tool as well as the
Low Delay SBR tool. The ER AAC ELD object type provides the ability to
extend the usage of generic low bitrate audio coding to applications
requiring a very low delay of the encoding / decoding chain (e.g.
full-duplex real-time communications)."

eAAC is a synonym for HE-AAC or aacPlus.

AAC-ELD is not compatible with HE-AAC. AAC-ELD is based on many of the
same principles as HE-AAC but they use different SBR variants and are
based on different bitstream syntax flavors.

Alex Converse

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