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MPEG4 AAC LD
pratheekp
post Jan 19 2011, 13:36
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Can MPEG4 AAC LD be made from AAC LC by reducing its main 4 delays without using LTP?? or is LTP a major component in AAC-LD???
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saratoga
post Jan 19 2011, 17:47
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QUOTE (pratheekp @ Jan 19 2011, 07:36) *
Can MPEG4 AAC LD be made from AAC LC by reducing its main 4 delays without using LTP?? or is LTP a major component in AAC-LD???


LTP is a dead and forgotten AAC extension. LD is the low delay profile for AAC. They're not really related. I don't know if its possible to use LTP with LD, but theres not much reason to want to.
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pratheekp
post Jan 20 2011, 05:34
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But in the MPEG4 spec its told that AAC-LD is the low delay profile for AAC-LTP....
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pratheekp
post Jan 20 2011, 09:40
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Can any1 provide me good links for ER AAC-LD coding...thanx in advance...
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pratheekp
post Jan 20 2011, 11:08
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delay in AAC-LC can be reduced using
1. 512/480 samples instead of 1024
2. No block switching
3. Filter bank delay
4. No(min) bit reservoir size

But how can we achieve these conditions?
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.alexander.
post Jan 20 2011, 11:18
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Level for the Low Delay AAC Profile:

Max channels/object 2, Max sample rate 48kHz, epConfig 0
LTP is not permitted. Pulse data is not permited.

QUOTE (pratheekp @ Jan 20 2011, 11:40) *
Can any1 provide me good links for ER AAC-LD coding...thanx in advance...


search mpegif.org mailing lists


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pratheekp
post Jan 21 2011, 14:04
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I want to include LTP in ER AAC LD profile. I want to know whether LTP can be optionally enabled or is it mandatory every time. Also if mandatory why....and if not why...pls answer...
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saratoga
post Jan 21 2011, 20:16
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QUOTE (pratheekp @ Jan 21 2011, 08:04) *
I want to include LTP in ER AAC LD profile.


LTP is a dead format. You do not want to include it with anything.

QUOTE (pratheekp @ Jan 21 2011, 08:04) *
I want to know whether LTP can be optionally enabled or is it mandatory every time. Also if mandatory why....and if not why...pls answer...


According to the post above yours, it is not allowed.
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C.R.Helmrich
post Jan 21 2011, 21:56
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IIRC all AAC LD flavors are based on AAC Low Complexity (LC). LTP is not allowed in LC because it increases the decoder (and also encoder) complexity significantly. LTP needs quite a lot of computation for little gain on "real-world" natural audio material.

Chris


--------------------
If I don't reply to your reply, it means I agree with you.
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pratheekp
post Jan 24 2011, 09:09
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Thanks to all who responded...bt i juz want to know that if i'm including LTP...even though it may lead to larger computation...do i have the option to optionally enable/disable the tool as it is possible with other tools in AAC
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.alexander.
post Jan 24 2011, 13:08
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QUOTE (C.R.Helmrich @ Jan 21 2011, 23:56) *
IIRC all AAC LD flavors are based on AAC Low Complexity (LC). LTP is not allowed in LC because it increases the decoder (and also encoder) complexity significantly. LTP needs quite a lot of computation for little gain on "real-world" natural audio material.

Chris


Decoding of LTP should not be computationally complex, what really makes AAC-LD decoder weird is ER related stuff like error-sensitivity categories and HCR.
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