[Mp4-tech] Enhanced HE-AAC baseline version

[Andreas Schneider]

Hi Anup,
anup kc <anupkc01 yahoo.com> wrote on 28/10/2023 06:26:52 AM:
> >Could you please point out to which part of the 3GPP specification you 
are 
> >referring?
> Hi Andreas
> 
> I was referring to the Encoder Spec doc- 3GPP TS 26.405 V1.0.0 
> (2004-05)- where in page 16 it said that 
> "frame_class - Is set to 0.
> num_env_idx - Is set to 0 if all values in the iid and icc vectors 
> after quantization are unchanged since previous frame.
> Is set to 1 for all other cases."
> If the maximum value of num_env_idx is 1 with frameclass always set 
> to 0 ,doesnt it mean that the maximum number of envelopes is 1 ?

This is correct. However, this is just the specification of the reference 
encoder. It points out that this particular encoder is internally limited 
to 1 envelope.
Hence this is not a normative statement that only 1 ps-envelope shall be 
used.
In fact, since baseline-ps and the unrestricted version of ps share the 
same bitstream format, a compliant encoder may also signal features that 
go beyond the capabilities of a baseline decoder (like IPD/OPD). So the 
limitation to baseline just places restrictions on decoder behaviour (i.e. 
disregard IPD/OPD-data, map 34 stereo bands to 20).
I hope this helps,
Andreas
> 
> -Anup
> 
> 
> Andreas Schneider <snd codingtechnologies.com> wrote:
> Hello Anup,
> Do you Yahoo!?
> Take Yahoo! Mail with you! Get it on your mobile phone.

--
Andreas Schneider, Research Engineer
Coding Technologies GmbH
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