Add --audio-output-buffer

On some systems, the SDL audio callback is not called frequently enough
(for example it requests 5ms of samples every 10ms), because the output
buffer is too small.

By default, we want to use a small value (5ms) to minimize latency and
buffer underrun, but if it does not work well, users need a way to
increase it.

Refs #3793 <https://github.com/Genymobile/scrcpy/issues/3793>

app/src/cli.c

@@ -71,6 +71,7 @@ enum {
     OPT_LIST_DISPLAYS,
     OPT_REQUIRE_AUDIO,
     OPT_AUDIO_BUFFER,
+    OPT_AUDIO_OUTPUT_BUFFER,
 };
 
 struct sc_option {
@@ -129,6 +130,16 @@ static const struct sc_option options[] = {
                 "likelyhood of buffer underrun (causing audio glitches).\n"
                 "Default is 50.",
     },
+    {
+        .longopt_id = OPT_AUDIO_OUTPUT_BUFFER,
+        .longopt = "audio-output-buffer",
+        .argdesc = "ms",
+        .text = "Configure the size of the SDL audio output buffer (in "
+                "milliseconds).\n"
+                "If you get \"robotic\" audio playback, you should test with "
+                "a higher value (10). Do not change this setting otherwise.\n"
+                "Default is 5.",
+    },
     {
         .longopt_id = OPT_AUDIO_CODEC,
         .longopt = "audio-codec",
@@ -1204,6 +1215,19 @@ parse_buffering_time(const char *s, sc_tick *tick) {
     return true;
 }
 
+static bool
+parse_audio_output_buffer(const char *s, sc_tick *tick) {
+    long value;
+    bool ok = parse_integer_arg(s, &value, false, 0, 1000,
+                                "audio output buffer");
+    if (!ok) {
+        return false;
+    }
+
+    *tick = SC_TICK_FROM_MS(value);
+    return true;
+}
+
 static bool
 parse_lock_video_orientation(const char *s,
                              enum sc_lock_video_orientation *lock_mode) {
@@ -1831,6 +1855,12 @@ parse_args_with_getopt(struct scrcpy_cli_args *args, int argc, char *argv[],
                     return false;
                 }
                 break;
+            case OPT_AUDIO_OUTPUT_BUFFER:
+                if (!parse_audio_output_buffer(optarg,
+                                               &opts->audio_output_buffer)) {
+                    return false;
+                }
+                break;
             default:
                 // getopt prints the error message on stderr
                 return false;