Take opus output gain into account when checking replaygain_limit peak (

cmus#1201)

* Add information about opus output gain to comments
* Add information about output gain to track_info struct
* Take output_gain into account when checking replaygain_limit
* Prevent output_gain comment from being overwriten by user comments
* Use keyvals_add instead of comments_add_const to avoid having to make output_gain "interesting"
* Use xmalloc0 in favor of xmalloc+memset for speed improvement
* Don't free val, since keyvals_add doesn't xstrdup it
* Initialize output_gain to 0 during track_info initialization
* Calculate peak from output_gain if missing, instead of doing a separate scale check

Co-authored-by: Rin Takanashi <[email protected]>

ip/opus.c

@@ -232,14 +232,24 @@ static int opus_read_comments(struct input_plugin_data *ip_data,
 	GROWING_KEYVALS(c);
 	struct opus_private *priv;
 	const OpusTags *ot;
+	const OpusHead *head;
 	int i;
 
 	priv = ip_data->private;
 
+	head = op_head(priv->of, -1);
+	if(head != NULL) {
+		char *val = xmalloc0(12); // 11 max int digits + NULL
+
+		snprintf(val, 12, "%d", head->output_gain);
+		keyvals_add(&c, "output_gain", val);
+	}
+
 	ot = op_tags(priv->of, -1);
 	if (ot == NULL) {
 		d_print("ot == NULL\n");
-		*comments = keyvals_new(0);
+		keyvals_terminate(&c);
+		*comments = c.keyvals;
 		return 0;
 	}
 

player.c

@@ -380,8 +380,8 @@ static void update_rg_scale(void)
 		return;
 	}
 	if (isnan(peak)) {
-		d_print("peak not available, defaulting to 1\n");
-		peak = 1;
+		d_print("peak not available, deriving from output gain\n");
+		peak = pow(10.0, player_info_priv.ti->output_gain / 20.0);
 	}
 	if (peak < 0.05) {
 		d_print("peak (%g) is too small\n", peak);

track_info.c

@@ -58,13 +58,15 @@ struct track_info *track_info_new(const char *filename)
 	ti->bpm = -1;
 	ti->codec = NULL;
 	ti->codec_profile = NULL;
+	ti->output_gain = 0;
 
 	return ti;
 }
 
 void track_info_set_comments(struct track_info *ti, struct keyval *comments) {
 	long int r128_track_gain;
 	long int r128_album_gain;
+	long int output_gain;
 
 	ti->comments = comments;
 	ti->artist = keyvals_get_val(comments, "artist");
@@ -110,6 +112,10 @@ void track_info_set_comments(struct track_info *ti, struct keyval *comments) {
 		ti->rg_album_gain = (r128_album_gain / 256.0) + 5;
 	}
 
+	if (comments_get_signed_int(comments, "output_gain", &output_gain) != -1) {
+		ti->output_gain = (output_gain / 256.0);
+	}
+
 	ti->collkey_artist = u_strcasecoll_key0(ti->artist);
 	ti->collkey_album = u_strcasecoll_key0(ti->album);
 	ti->collkey_title = u_strcasecoll_key0(ti->title);

track_info.h

@@ -46,6 +46,7 @@ struct track_info {
 	double rg_track_peak;
 	double rg_album_gain;
 	double rg_album_peak;
+	double output_gain;
 	const char *artist;
 	const char *album;
 	const char *title;