player: add --audio-stream-silence

Completely insane that this has to be done. Crap for compensating HDMI
crap.

DOCS/man/options.rst

@@ -1341,6 +1341,17 @@ Audio
 
     Default: 0.2 (200 ms).
 
+``--audio-stream-silence=<yes|no>``
+    Cash-grab consumer audio hardware (such as A/V receivers) often ignore
+    initial audio sent over HDMI. This can happen every time audio over HDMI
+    is stopped and resumed. In order to compensate for this, you can enable
+    this option to not to stop and restart audio on seeks, and fill the gaps
+    with silence. Likewise, when pausing playback, audio is not stopped, and
+    silence is played while paused. Note that if no audio track is selected,
+    the audio device will still be closed immediately.
+
+    Not all AOs support this.
+
 Subtitles
 ---------
 

audio/out/ao.c

@@ -183,6 +183,8 @@ static struct ao *ao_init(bool probing, struct mpv_global *global,
     ao->api_priv = talloc_zero_size(ao, ao->api->priv_size);
     assert(!ao->api->priv_defaults && !ao->api->options);
 
+    ao->stream_silence = flags & AO_INIT_STREAM_SILENCE;
+
     int r = ao->driver->init(ao);
     if (r < 0) {
         // Silly exception for coreaudio spdif redirection

audio/out/ao.h

@@ -56,6 +56,8 @@ enum {
     // Only accept multichannel configurations that are guaranteed to work
     // (i.e. not sending arbitrary layouts over HDMI).
     AO_INIT_SAFE_MULTICHANNEL_ONLY = 1 << 1,
+    // Stream silence as long as no audio is playing.
+    AO_INIT_STREAM_SILENCE = 1 << 2,
 };
 
 typedef struct ao_control_vol {

audio/out/internal.h

@@ -44,6 +44,7 @@ struct ao {
     struct input_ctx *input_ctx;
     struct mp_log *log; // Using e.g. "[ao/coreaudio]" as prefix
     int init_flags; // AO_INIT_* flags
+    bool stream_silence;        // if audio inactive, just play silence
 
     // The device as selected by the user, usually using ao_device_desc.name
     // from an entry from the list returned by driver->list_devices. If the

audio/out/pull.c

@@ -185,7 +185,7 @@ static double get_delay(struct ao *ao)
 static void reset(struct ao *ao)
 {
     struct ao_pull_state *p = ao->api_priv;
-    if (ao->driver->reset)
+    if (!ao->stream_silence && ao->driver->reset)
         ao->driver->reset(ao); // assumes the audio callback thread is stopped
     set_state(ao, AO_STATE_NONE);
     for (int n = 0; n < ao->num_planes; n++)
@@ -195,7 +195,7 @@ static void reset(struct ao *ao)
 
 static void pause(struct ao *ao)
 {
-    if (ao->driver->reset)
+    if (!ao->stream_silence && ao->driver->reset)
         ao->driver->reset(ao);
     set_state(ao, AO_STATE_NONE);
 }
@@ -244,6 +244,10 @@ static int init(struct ao *ao)
         p->buffers[n] = mp_ring_new(ao, ao->buffer * ao->sstride);
     atomic_store(&p->state, AO_STATE_NONE);
     assert(ao->driver->resume);
+
+    if (ao->stream_silence)
+        ao->driver->resume(ao);
+
     return 0;
 }
 

options/options.c

@@ -396,6 +396,7 @@ const m_option_t mp_opts[] = {
     OPT_STRING("audio-device", audio_device, 0),
     OPT_STRING("audio-client-name", audio_client_name, 0),
     OPT_FLAG("audio-fallback-to-null", ao_null_fallback, 0),
+    OPT_FLAG("audio-stream-silence", audio_stream_silence, 0),
     OPT_CHOICE("force-window", force_vo, 0,
                ({"no", 0}, {"yes", 1}, {"immediate", 2})),
     OPT_FLAG("taskbar-progress", vo.taskbar_progress, 0),

options/options.h

@@ -87,6 +87,7 @@ typedef struct MPOpts {
     char *audio_device;
     char *audio_client_name;
     int ao_null_fallback;
+    int audio_stream_silence;
     int force_vo;
     int softvol;
     float softvol_volume;

player/audio.c

@@ -382,6 +382,9 @@ static void reinit_audio_filters_and_output(struct MPContext *mpctx)
         if (!opts->audio_output_channels.set || opts->audio_output_channels.auto_safe)
             ao_flags |= AO_INIT_SAFE_MULTICHANNEL_ONLY;
 
+        if (opts->audio_stream_silence)
+            ao_flags |= AO_INIT_STREAM_SILENCE;
+
         mp_chmap_sel_list(&afs->output.channels, opts->audio_output_channels.chmaps,
                           opts->audio_output_channels.num_chmaps);