[M4IF Technotes] escape codeword header

[Chien-Hsin Lin]

Hi! Peter:
I thought the formules are used when you decode the run and level in the
bitstreams then we apply the adjustment for decoding.
What I would like to know is the encoding the VLC codeword with ESC type 1
and typ2
So, the original LEVEL and RUN like
LEVEL_S - LMAX   = sign(LEVEL) * abs(LEVEL)
RUN_S - RMAX - 1 = RUN
The left hand parts are the new (LEVEL_S - LMAX) and (RUN_S - RUNMAX-1) for
TCOEF lookup and right hand sides of RUN and LEVEL are the result when we do
the run length encoding.
Please correct me if I am wrong about the encoding part?
Thanks for the answering my questions.
Chien-Hsin Lin
on 8/17/01 6:14 PM, Peter Haighton at peterh   videospheres.com wrote:
> Hello Chien-Hsin,
> 
> You are mostly correct.  You use the VLC encoded after the escape code and
> then use the following formulas.
> 
> For type 1: LEVEL= sign(LEVEL) x [ abs( LEVEL) + LMAX ]
> For type 2: RUN= RUN + RMAX + 1
> 
> Peter
> --
> Peter Haighton
> VideoSpheres Inc.
> 84 Hines Road
> Kanata, Ontario
> Canada, K2K 3G3
> Tel: (613) 270-9646 x3022
> Fax: (613) 271-9442
> email: peterh   VideoSpheres.com
> 
> See http://www.m4if.org for the latest on MPEG-4
> 
> 
> -----Original Message-----
> From: technotes-admin   lists.m4if.org
> [mailto:technotes-admin   lists.m4if.org]On Behalf Of Chien-Hsin Lin
> Sent: Friday, August 17, 2023 1:58 PM
> To: technotes   lists.m4if.org; chlin   apple.com
> Subject: [M4IF Technotes] escape codeword header
> 
> 
> Hi!
> 
> I have some question regarding the escape type 1 and type 2
> It seems to me for type 1 ESC where ESC + "0" is the header part and
> codeword is encoded by Table B-16 and B-17 table with adjustment for
> LEVEL-LEVEL_MAX(from L MAX table).
> 
> And type is ESC+"10" followed by new run which is RUN-RUN_MAX from R MAX
> table.
> The formats are
> 
> 
> 1. Type 1: ESC (0000_011) + "0" + new codeword based on (L-L_MAX)
> 2. Type 2: ESC (0000_011) +"10" + new codeword based on (R-R_MAX)
> 
> 
> I would like to know if that is correct or did I miss something else?
> 
> Thanks
> 
> 
> 
> Chien-Hsin Lin
> 
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