player: redo how stream caching and pausing on low cache works

Add the --cache-secs option, which literally overrides the value of
--demuxer-readahead-secs if the stream cache is active. The default
value is very high (10 seconds), which means it can act as network
cache.

Remove the old behavior of trying to pause once the byte cache runs
low. Instead, do something similar wit the demuxer cache. The nice
thing is that we can guess how many seconds of video it has cached,
and we can make better decisions. But for now, apply a relatively
naive heuristic: if the cache is below 0.5 secs, pause, and wait
until at least 2 secs are available.

Note that due to timestamp reordering, the estimated cached duration
of video might be inaccurate, depending on the file format. If the
file format has DTS, it's easy, otherwise the duration will seemingly
jump back and forth.

1 files changed, 6 insertions, 0 deletions

diff --git a/demux/demux.h b/demux/demux.h
index 92ef461077..d0f70c6f57 100644
--- a/demux/demux.h
+++ b/demux/demux.h
@@ -54,6 +54,12 @@ enum demux_ctrl {
     DEMUXER_CTRL_RESYNC,
     DEMUXER_CTRL_IDENTIFY_PROGRAM,
     DEMUXER_CTRL_STREAM_CTRL,
+    DEMUXER_CTRL_GET_READER_STATE,
+};
+
+struct demux_ctrl_reader_state {
+    bool eof, underrun, idle;
+    double ts_range[2]; // start, end
 };
 
 struct demux_ctrl_stream_ctrl {