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[non-BE] Resolve "Dry 2dir MASA encoded incorrectly"

Tapani Pihlajakuja requested to merge 1034-dry-2dir-masa-encoded-incorrectly into main

Reason why this change is needed

With a relatively specific MASA format input where the scene is acoustically dry and there is a single source analysed into the second direction of MASA format, the MASA metadata encoding path can result in wrong preprocessing of metadata. This results in wrong values being encoded and poor quality in the end.

Description of the change

The fix in general changes to use of correct number of directions in the energy ratio compensation function (thus avoiding incorrect energy ratios) and specifically also adds copying of spherical indices in addition to azimuth and elevation in encoder when metadata is moved as it spherical indices are also sometimes directly used in encoding.

Update: As a result of further analysis of LTV test run, it became evident that there is also a similar case where first direction of 2dir data contains the active direction. In this case, the difference is not too audible but it is non-BE due to changing direction encoding accuracy.

Update 2: Analysing LTV test run of OMASA also lead to a fix in direction metadata combining function to ensure that OMASA premixing at low bitrates results in proper MASA format in the energy ratio sense. It was also noted that the ratio threshold for "silent direction" should be a bit smaller than it was.

Affected operating points

  • The produced bitstream changes for all MASA operating points (into correct one) when the input content is specific to the case. Thus, also output is non-BE when this happens.
  • The produced bitstream changes also for all OMASA operating points when condition is met.
  • The produced bitstream should be interoperable as only the preprocessing of metadata is changed and bitstream encoding does not change.
Edited by Tapani Pihlajakuja

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