3.1.8.1.2 Sub-Band Diffing

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Sub-band diffing is used to determine whether a difference tile or an original tile is sent to the RLGR Entropy Encoder ([MS-RDPRFX] section 3.1.8.1.7).

The sending of an original tile entails dispatching the nine non-LL3 bands and the deltas of the LL3 band to the RLGR Entropy Encoder. An LL3 delta is defined as the difference between a given LL3 element and the previous element within the same tile. The first LL3 element is transmitted without modification. The differences in the LL3 band are denoted as DwtQ-LL-Deltas.

Sending an original tile to the RLGR Entropy Encoder is represented as:

DwtQ-NonLL, DwtQ-LL-Deltas -> RLGR Entropy Encoder

A difference tile is defined as the difference between the DwtQ elements of two consecutive frames Fm and Fn (where m > n):

Diffm = DwtQm - DwtQn

Diff is composed of Diff-LL and Diff-NonLL. All the bands of a diff tile are sent to the RLGR Entropy Encoder:

Diff-NonLL, Diff-LL -> RLGR Entropy Encoder