player/CrossFade: do not cross-fade songs shorter than 20 seconds

NEWS

@@ -16,6 +16,8 @@ ver 0.23 (not yet released)
 * decoder
   - openmpt: new plugin
   - wavpack: fix WVC file support
+* player
+  - do not cross-fade songs shorter than 20 seconds
 * output
   - oss: support DSD over PCM
   - pipewire: new plugin

src/player/CrossFade.cxx

@@ -34,6 +34,7 @@ inline bool
 CrossFadeSettings::CanCrossFadeSong(SignedSongTime total_time) const noexcept
 {
 	return !total_time.IsNegative() &&
+		duration >= MIN_TOTAL_TIME &&
 		duration >= std::chrono::duration_cast<FloatDuration>(total_time);
 }
 
@@ -94,7 +95,8 @@ mixramp_interpolate(const char *ramp_list, float required_db) noexcept
 }
 
 unsigned
-CrossFadeSettings::Calculate(SignedSongTime total_time,
+CrossFadeSettings::Calculate(SignedSongTime current_total_time,
+			     SignedSongTime next_total_time,
 			     float replay_gain_db, float replay_gain_prev_db,
 			     const char *mixramp_start, const char *mixramp_prev_end,
 			     const AudioFormat af,
@@ -104,7 +106,8 @@ CrossFadeSettings::Calculate(SignedSongTime total_time,
 	unsigned int chunks = 0;
 
 	if (!IsEnabled() ||
-	    !CanCrossFadeSong(total_time) ||
+	    !CanCrossFadeSong(current_total_time) ||
+	    !CanCrossFadeSong(next_total_time) ||
 	    /* we can't crossfade when the audio formats are different */
 	    af != old_format)
 		return 0;

src/player/CrossFade.hxx

@@ -27,6 +27,11 @@ class SignedSongTime;
 
 struct CrossFadeSettings {
 	/**
+	 * Songs shorter than this will never cross-fade.
+	 */
+	static constexpr SignedSongTime MIN_TOTAL_TIME{std::chrono::seconds{20}};
+
+	/**
 	 * The configured cross fade duration [s].
 	 */
 	FloatDuration duration{0};
@@ -46,7 +51,8 @@ struct CrossFadeSettings {
 	/**
 	 * Calculate how many music pipe chunks should be used for crossfading.
 	 *
-	 * @param total_time total_time the duration of the new song
+	 * @param current_total_time the duration of the current song
+	 * @param next_total_time the duration of the new song
 	 * @param replay_gain_db the ReplayGain adjustment used for this song
 	 * @param replay_gain_prev_db the ReplayGain adjustment used on the last song
 	 * @param mixramp_start the next songs mixramp_start tag
@@ -58,7 +64,8 @@ struct CrossFadeSettings {
 	 * should be disabled for this song change
 	 */
 	[[gnu::pure]]
-	unsigned Calculate(SignedSongTime total_time,
+	unsigned Calculate(SignedSongTime current_total_time,
+			   SignedSongTime next_total_time,
 			   float replay_gain_db, float replay_gain_prev_db,
 			   const char *mixramp_start,
 			   const char *mixramp_prev_end,

src/player/Thread.cxx

@@ -1049,7 +1049,8 @@ Player::Run() noexcept
 			   calculate how many chunks will be required
 			   for it */
 			cross_fade_chunks =
-				pc.cross_fade.Calculate(dc.total_time,
+				pc.cross_fade.Calculate(pc.total_time,
+							dc.total_time,
 							dc.replay_gain_db,
 							dc.replay_gain_prev_db,
 							dc.GetMixRampStart(),