When playing a stream, the input metadata is transferred to the queue_item.
However, that was not done if there was no input metadata, which meant that
old metadata was not getting erased.
When pipe playback is started, but no data is written to the pipe, the input
loop would bring the cpu to 100%. This fix limits the loop like it was before
player refactor.
This fixes a bug from commit 37ce8dd6 where seek_http (which is called when
pausing playback) for non-seekable streams would return -1, thus signalling
an error, even though it is not. The player would think that the stream
could not be played and then skip to the next item.
This change is preparation to use ffmpeg's resampling capabilities to keep local
audio in sync (by up/downsampling slightly). This requires that sample rates are
not fixed for a transcode profile.
Added benefit of this is that we don't need quite as many xcode profiles.
rescaling, meaning we can do without parallel ffmpeg interfaces.
This also moves artwork rescaling from libswscale to libavfilter, which
seems to fix a problem with PNG rescaling.
