In order to compute a THD score, a pure tone must be used as input signal.
Also, its frequency must be known. For this reason, this CL adds a number of
changes in the APM-QA pipeline. More in detail, input signal metadata is loaded
and passed to the THD evaluation score instance. This makes the eval_scores
module less reusable, but it is fine since the module has been specifically
designed for the APM-QA module.
BUG=webrtc:7494
Review-Url: https://codereview.webrtc.org/3010413002
Cr-Commit-Position: refs/heads/master@{#19970}
5d26edcc02