vc2-maximum-quantisation-index

Compute the maximum quantisation index which is useful for a particular VC-2 codec configuration.

Using the same approach as the vc2-bit-widths-table command, this command works out the most extreme values which a VC-2 quantiser might encounter (given certain assumptions about the behaviour of the encoder design, see Caveats). Using this information, it is possible to find the smallest quantisation index sufficient to quantise all transform coefficients to zero.

Though the VC-2 standard does not rule out larger quantisation indices being used, there is no reason for a sensible encoder implementation to use such a any larger quantisation index.

Note

The values printed by this tool are valid only for the wavelet transform, depth, picture bit width and quantisation matrix specified. See Caveats for further limitations and assumptions made by this software.

Example usage

$ vc2-static-filter-analysis \
    --wavelet-index le_gall_5_3 \
    --dwt-depth 2 \
    --output static_analysis.json

$ vc2-maximum-quantisation-index \
    static_analysis.json \
    --picture-bit-width 10 \
    --custom-quantisation-matrix \
        0 LL 1 \
        1 HL 2   1 LH 0   1 HH 4 \
        2 HL 1   2 LH 3   2 HH 3
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Arguments

The complete set of arguments can be listed using --help

usage: vc2-maximum-quantisation-index [-h] --picture-bit-width
                                      PICTURE_BIT_WIDTH
                                      [--custom-quantisation-matrix CUSTOM_QUANTISATION_MATRIX [CUSTOM_QUANTISATION_MATRIX ...]]
                                      [--verbose]
                                      static_filter_analysis

Compute the maximum quantisation index which is useful for a particular VC-2
codec configuration.

positional arguments:
  static_filter_analysis
                        The static analysis JSON data produced by vc2-static-
                        filter-analysis.

optional arguments:
  -h, --help            show this help message and exit
  --picture-bit-width PICTURE_BIT_WIDTH, -b PICTURE_BIT_WIDTH
                        The number of bits in the picture signal.
  --custom-quantisation-matrix CUSTOM_QUANTISATION_MATRIX [CUSTOM_QUANTISATION_MATRIX ...], -q CUSTOM_QUANTISATION_MATRIX [CUSTOM_QUANTISATION_MATRIX ...]
                        Define the custom quantisation matrix used by a codec.
                        Optional except for filters without a default
                        quantisation matrix defined. Should be specified as a
                        series 3-argument tuples giving the level, orientation
                        and quantisation matrix value for every entry in the
                        quantisation matrix.
  --verbose, -v         Show more detailed status information during
                        execution.