Fix #1595: Set ptl_multi_layer_enabled_flag when more than one layer is encoded

This solution sets ptl_multi_layer_enabled_flag automatically, when more than one layer is encoded.

This reduces the usefulness of the MultiLayerEnabledFlag command line parameter to the case, where enabling the flag for a single layer is wanted.

An alternative solution would be to fail instead of a warning and ask the user to manually enable MultiLayerEnabledFlag.

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• 27582af8 - Fix #1595: Set ptl_multi_layer_enabled_flag when more than one layer is encoded

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• c77e5dab - Fix #1595: Set ptl_multi_layer_enabled_flag when more than one layer is encoded

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mentioned in commit cac89561

I found this fix causes encoder crash for the case of additional conformance test for multilayer coding, specifically, the case of OLSMultiProfile_A_NHK.

The purpose of the conformance test is to validate the backward compatibility, where the base layer is coded with PTL indicating main10 with ptl_multilayer_enabled_flag equal to 0 whereas the enhancement layer is coded with PTL indicating multilayer main 10 with ptl_multilayer_enabled_flag equal to 1. command line example is as follows:

EncoderApp.exe -c encoder_randomaccess_vtm.cfg -c two_layers_multi_profiles.cfg -l0 --Profile=main_10 -l1 --Profile=multilayer_main_10 -l1 --MultiLayerEnabledFlag=1

The code changes by this MR forcibly set the ptl_multilayer_enabled_flag qeual to 1 whenever the number of layers are greater than 1, so PTL indicating main10 with ptl_multilayer_enabled_flag equal to 1 is generated which is violating the specifications.

To make the software easier for everyone to test multilayer coding functionality, I suggest the following changes:

• revert the code changes.
• add "MultiLayerEnabledFlag : 1" to multi-layer configurations (e.g. two_layers.cfg, etc)

By doing so, no one needs to care about --MultiLayerEnabledFlag for the most multilayer coding test cases. Only for the case of OLSMultiProfile_A_NHK, the encoder crash can be avoided by the following command:

EncoderApp.exe -c encoder_randomaccess_vtm.cfg -c two_layers_multi_profiles.cfg -l0 --Profile=main_10 -l1 --Profile=multilayer_main_10 -l0 --MultiLayerEnabledFlag=0

@s.iwamura Can you submit a merge request with your suggestions? Thanks.

@bossen submitted !2582 (merged)

mentioned in merge request !2582 (merged)

mentioned in commit b484700e

mentioned in commit 886fe038