The question of whether or not one is wasting bandwidth is based on how the
alt-ref frame is generated and used for prediction of other frames. It is
possible to increase bitrate if one inserts a alt-frame with not much
information and which no other frame refers to. But in general a judicious
use of alt-ref frame is intended to reduce the bitrate.
Recommended frequency - Depends on application, complexity and the content.
And I think ref encoder can generate alt-ref frames.
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Analogue and Digital Integrated Circuit Design
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