The code related to config parameters LambdaModifier0 through LambdaModifier3 has two problems.

First, the code does not use temporal_id to select what LambdaModifier to apply for a picture.This means that picture structures that are not dyadic will get incorrect lambdas if LambdaModifierX are specified.

Second, LambdaModifierX used for temporal layers above 3 are uninitialized. In practice, this may cause severe compression efficiency losses for some pictures when the GOP size is 16 or larger.

Neither of these problems affect any of the common condition picture structures.

The attached patch fixes the problem by adding new initialized parameters LambdaModifier4 through LambdaModifier7, and using the temporal layer as read from the config file as index instead of selecting LambdaModifier based on the GOP size.