[M4IF Technotes] Method 1 Quantisation

[Peter Haighton]

Hi Yossi,
The standard states that
level = dc_coeff//dc_scaler but it also says that for
H.263 (short header=1) dc_scaler is always 8
so that means that both sections are correct.
Hope this helps
Peter
-----Original Message-----
From: technotes-admin   lists.m4if.org
[mailto:technotes-admin   lists.m4if.org]On Behalf Of Yossi
Sent: Tuesday, June 05, 2023 10:02 AM
To: technotes   lists.m4if.org
Subject: [M4IF Technotes] Method 1 Quantisation
Sirs,
MPEG4 Video Verification Model (VM 16.0) presents two quantisation methods:
H263 and MPEG4 (pp. 61-63).
Section 3.4.4.2 describes Method 1 (H263), where Intra DC quantisation is
level = dc_coeff // 8
Section 3.4.5.1.1 describes Method 2 (MPEG4), where Intra DC quantisation is
level = dc_coeff//dc_scaler, where dc_scaler is a non-linear scaler based on
Qp.
However, Section 3.4.5.1.1 states, "Note: This section is valid for H.263
quantisation also."
Is the Intra DC quantisation method presented in Sec. 3.4.4.2 incorrect? In
particular, I am looking at the Simple Profile that allows only Method 1 for
quantization (see Table 9-1 in Part 2 of the MPEG4 Standard, page 201).
Should Intra DC quantisation for Simple Profile follow Section 3.4.4.2 or
Section 3.4.5.1.1?
Thank you,
Yossi Shain
NeoMagic Israel
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