[SLS-DC] [EXTERNAL] Re: 123B2 Corrigendum

Wed Aug 4 14:48:55 UTC 2021

Hi Aaron,

Is it correct to assume for D=3 case defined in current definition k_z(t)=2, although rare,  the compression is not optimal under the high entropy mode? Or, possibly not compressing?
I agree with the changes proposed to put D=3 to be all low entropy samples if high entropy condition is rare. Also, I agree the note in 5.4.3.3.5.1.4 needs to be updated as well.

Best,
Mark Wong
NASA GSFC Flight Microwave & Telecommunication Systems Branch
Phone: 1-301-286-6549

From: SLS-DC <sls-dc-bounces at mailman.ccsds.org> On Behalf Of Gian.Paolo.Calzolari at esa.int
Sent: Wednesday, August 4, 2021 4:26 AM
To: Roberto.Camarero at esa.int
Cc: sls-dc at mailman.ccsds.org; SLS-DC <sls-dc-bounces at mailman.ccsds.org>
Subject: [EXTERNAL] Re: [SLS-DC] 123B2 Corrigendum

Just an hint.
We have already a Technical Corrigendum 3 to CCSDS 123.0-B-2, Issued February 2019 and I fear the (unwritten)  rule is that 3 is the maximum number of corrigenda.
Therefore you better check with Tom (cc'ed here) about this.

CIao

Gian Paolo
(Not AD :o)

From:        Roberto.Camarero at esa.int<mailto:Roberto.Camarero at esa.int>
To:        "Kiely, Aaron B (US 332B)" <aaron.b.kiely at jpl.nasa.gov<mailto:aaron.b.kiely at jpl.nasa.gov>>
Cc:        "sls-dc at mailman.ccsds.org<mailto:sls-dc at mailman.ccsds.org>" <sls-dc at mailman.ccsds.org<mailto:sls-dc at mailman.ccsds.org>>
Date:        04-08-21 09:52
Subject:        Re: [SLS-DC] 123B2 Corrigendum
Sent by:        "SLS-DC" <sls-dc-bounces at mailman.ccsds.org<mailto:sls-dc-bounces at mailman.ccsds.org>>
________________________________

Dear Aaron, dear all,

Good catch Aaron.
My only question would be if we are not missing a definition for t>0 and D=3 in that case, in which k_z(t)=1 should be used according to Annex F in the Green Book.
If not, I understand that by this change we force D=3 samples to be encoded with low entropy codes only. In that case we should probably also change Annex F and the Note in 5.4.3.3.5.1.4 to "When D<=3, the condition...".

Kind regards,

Roberto

ESA - European Space Agency
Roberto Camarero
Onboard Payload Data Processing Engineer
TEC-EFD / Electrical Engineering Department
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From:        "Kiely, Aaron B (US 332B)" <aaron.b.kiely at jpl.nasa.gov<mailto:aaron.b.kiely at jpl.nasa.gov>>
To:        "sls-dc at mailman.ccsds.org<mailto:sls-dc at mailman.ccsds.org>" <sls-dc at mailman.ccsds.org<mailto:sls-dc at mailman.ccsds.org>>
Date:        08/04/2021 12:52 AM
Subject:        [SLS-DC] 123B2 Corrigendum
Sent by:        "SLS-DC" <sls-dc-bounces at mailman.ccsds.org<mailto:sls-dc-bounces at mailman.ccsds.org>>
________________________________

Dear Working Group,

There is a minor issue with 123B2.

The NOTE in 5.4.3.3.5.2 of 123B2 states that, "For high-entropy samples, it can be shown that k_z(t)>=2." In fact, as the standard is written this isn't true, it's just extremely rare - it can only happen when bit depth is D=3. (See Annex F of the Green Book.)

We intended for the idea of this note to be normative, eliminating the need to implement a code that would be used only for a very special case. I believe we should request a corrigendum to do the following:
               1.    In 5.4.3.3.5.2, change
                                                 k_z(t) is the largest positive integer k_z(t)<=max{D-2,2}, such that...
                                to
                                                 k_z(t) is the largest integer 2<=k_z(t)<=max{D-2,2}, such that...
               2.     Delete the NOTE in 5.4.3.3.5.2.
               3.    In 5.4.3.3.5.1.4, change
                                                 For t>0...
                                to
                                                 For t>0 and D>3, ...

Please let me know if this looks right, and if we have consensus I'll forward this to the Editor and Area Director.

Thanks,
Aaron[attachment "smime.p7s" deleted by Roberto Camarero/estec/ESA]
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