Cut off a choked demuxer's output codec/filter queues, effectively preventing
them from processing packets while the demuxer is choked. Avoids downstream
nodes from piling up extra input that a demuxer shouldn't currently be
sending.
The main benefit of this is to avoid queuing up excess packets that don't want
to be decoded yet, reducing memory consumption for idle inputs by preventing
them from being read earlier than needed.
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