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Old 11th February 2019, 01:30   #1  |  Link
Join Date: Apr 2009
Location: North Europe
Posts: 518
Speech-encoding at low bitrate with AAC?

I'm trying to find out what type of setting I should use to encode audio (speech mostly) at ~64kbps with Apple AAC-codec.
Is Apple CVBR (Constrained VBR), with HE-AAC enabled, better to use when encoding low bitrate, than using normal Apple VBR (also called TVBR, I think. LC-AAC)?

This ABX-test uses Apple CVBR (with HE-AAC enabled) and not normal Apple VBR (also called TVBR, I think) when comparing codecs at low bitrate,
"Public Multiformat Listening Test @ ~64 kbps (March 2011)",

At 96kbps bitrate, IgorC wrote this though:
TVBR - --tvbr 46 - real bitrate ~94-95 kbps - have score 4,391 in public test
CVBR --cvbr 96 - real bitrate ~100-101 kbps - score is 4,342.

It's bitrate variation. Both CVBR and TVBR are pretty the same.
Use any of them.

EDIT: Thanks for the answer tebasuna51 & SeeMoreDigital!

Last edited by Forteen88; 12th February 2019 at 11:43. Reason: thanking
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Old 11th February 2019, 10:22   #2  |  Link
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Join Date: Feb 2005
Location: Spain
Posts: 6,051
The difference between LC-AAC (TVBR allowed) and HE-AAC (TVBR not available) is the use of SBR (Spectral Band Replication) for high frequencies in HE.

LC-AAC is better than HE-AAC with bitrates over 96 Kb/s, HE-AAC is better with bitrates below 96 Kb/s.

If you want ~64kbps you must use HE-AAC CVBR.
BeHappy, AviSynth audio transcoder.
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Old 11th February 2019, 17:35   #3  |  Link
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Join Date: Jun 2003
Location: Notts, UK
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HE-AAC v2 (SBR with Parametric stereo)?!

See here for more info: https://forum.doom9.org/showthread.p...14#post1789614
| I've been testing hardware media playback devices and software A/V encoders and decoders since 2001 | My Network Layout & A/V Gear |

Last edited by SeeMoreDigital; 11th February 2019 at 23:15.
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