player: use fixed timeout for cache pausing (buffering) duration

This tried to be clever by waiting for a longer time each time the
buffer was underrunning, or shorter if it was getting better. I think
this was pretty weird behavior and makes no sense. If the user really
wants the stream to buffer longer, he/she/it can just pause the player
(the network caches will continue to be filled until they're full).
Every time I actually noticed this code triggering in my own use, I
didn't find it helpful. Apart from that it was pretty hard to test.

Some waiting is needed to avoid that the player just plays the available
data as fast as possible (to compensate for late frames and underrunning
audio). Just use a fixed wait time, which can now be controlled by the
new --cache-pause-wait option.

DOCS/man/options.rst

@@ -3856,6 +3856,15 @@ Cache
     data and stalls decoding/playback (default: yes). If enabled, it will
     pause and unpause once more data is available, aka "buffering".
 
+``--cache-pause-wait=<seconds>``
+    Number of seconds the packet cache should have buffered before starting
+    playback again if "buffering" was entered (default: 1). This can be used
+    to control how long the player rebuffers if ``--cache-pause`` is enabled,
+    and the demuxer underruns. If the given time is higher than the maximum
+    set with ``--cache-secs`` or  ``--demuxer-readahead-secs``, or prefetching
+    ends before that for some other reason (like file end), playback resumes
+    earlier.
+
 
 Network
 -------

options/options.c

@@ -451,6 +451,7 @@ const m_option_t mp_opts[] = {
     OPT_FLAG("demuxer-thread", demuxer_thread, 0),
     OPT_FLAG("prefetch-playlist", prefetch_open, 0),
     OPT_FLAG("cache-pause", cache_pausing, 0),
+    OPT_FLOAT("cache-pause-wait", cache_pause_wait, M_OPT_MIN, .min = 0),
 
     OPT_DOUBLE("mf-fps", mf_fps, 0),
     OPT_STRING("mf-type", mf_type, 0),
@@ -894,6 +895,7 @@ const struct MPOpts mp_default_opts = {
     .demuxer_thread = 1,
     .hls_bitrate = INT_MAX,
     .cache_pausing = 1,
+    .cache_pause_wait = 1.0,
     .chapterrange = {-1, -1},
     .ab_loop = {MP_NOPTS_VALUE, MP_NOPTS_VALUE},
     .edition_id = -1,

options/options.h

@@ -263,6 +263,7 @@ typedef struct MPOpts {
     char *sub_demuxer_name;
 
     int cache_pausing;
+    float cache_pause_wait;
 
     struct image_writer_opts *screenshot_image_opts;
     char *screenshot_template;

player/core.h

@@ -432,7 +432,7 @@ typedef struct MPContext {
     bool playing_msg_shown;
 
     bool paused_for_cache;
-    double cache_stop_time, cache_wait_time;
+    double cache_stop_time;
     int cache_buffer;
 
     // Set after showing warning about decoding being too slow for realtime

player/playloop.c

@@ -234,7 +234,6 @@ void reset_playback_state(struct MPContext *mpctx)
     mpctx->current_seek = (struct seek_params){0};
     mpctx->playback_pts = MP_NOPTS_VALUE;
     mpctx->last_seek_pts = MP_NOPTS_VALUE;
-    mpctx->cache_wait_time = 0;
     mpctx->step_frames = 0;
     mpctx->ab_loop_clip = true;
     mpctx->restart_complete = false;
@@ -620,14 +619,8 @@ static void handle_pause_on_low_cache(struct MPContext *mpctx)
     if (mpctx->restart_complete && use_pause_on_low_cache) {
         if (mpctx->paused && mpctx->paused_for_cache) {
             if (!s.underrun && (!opts->cache_pausing || s.idle ||
-                                s.ts_duration >= mpctx->cache_wait_time))
+                                s.ts_duration >= opts->cache_pause_wait))
             {
-                double elapsed_time = now - mpctx->cache_stop_time;
-                if (elapsed_time > mpctx->cache_wait_time) {
-                    mpctx->cache_wait_time *= 1.5 + 0.1;
-                } else {
-                    mpctx->cache_wait_time /= 1.5 - 0.1;
-                }
                 mpctx->paused_for_cache = false;
                 update_internal_pause_state(mpctx);
                 force_update = true;
@@ -641,10 +634,9 @@ static void handle_pause_on_low_cache(struct MPContext *mpctx)
                 force_update = true;
             }
         }
-        mpctx->cache_wait_time = MPCLAMP(mpctx->cache_wait_time, 1, 10);
         if (mpctx->paused_for_cache) {
             cache_buffer =
-                100 * MPCLAMP(s.ts_duration / mpctx->cache_wait_time, 0, 0.99);
+                100 * MPCLAMP(s.ts_duration / opts->cache_pause_wait, 0, 0.99);
         }
     }