From 27a604bd5657f53412fa1d7e95e557cad591bc8f Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <icculus@icculus.org>
Date: Sun, 9 Nov 2003 20:11:30 +0000
Subject: [PATCH] (Courtesy of Jerome Zago on the SDL mailing list...)

+++++ Synopsis:
Mix_FadeInMusic(Music, 0, chunksize) following Mix_VolumeMusic(0) doesn't take
into account the latter for low values of "chunksize" when "Music" is a mod.

+++++ How to reproduce the problem:
#####
$ cat testmusic.c
#include <SDL/SDL.h>
#include <SDL/SDL_mixer.h>
#include <stdlib.h>

int main (int argc, char **argv)
{
  if (argc != 4) {
    fprintf(stderr, "Usage: %s <music file> <chunksize> <ms>\n", argv[0]);
    return 1;
  }

  if (SDL_Init(SDL_INIT_AUDIO) >= 0) {
    if (Mix_OpenAudio(44100, AUDIO_S16, 1, atoi(argv[2])) >= 0) {
      Mix_Music* Music = Mix_LoadMUS(argv[1]);
      if (Music) {
        Mix_VolumeMusic(0);
        Mix_FadeInMusic(Music, 0, atoi(argv[3]));
        printf("Now playing\n");
        SDL_Delay(2000);
        Mix_FreeMusic(Music);
      }
    }
  }
  SDL_Quit();
  return 0;
};

$ cc -g -O2 -Wall -I/usr/include/SDL -D_REENTRANT  -L/usr/lib -lSDL \
   -lpthread -lSDL_mixer  testmusic.c   -o testmusic

$ ./testmusic /usr/local/share/heroes/mod/heroes01.xm 512 10
Now playing
[ I hear the music => BAD ]

$ ./testmusic /usr/local/share/heroes/mod/heroes01.xm 512 11
Now playing
[ I don't hear the music => GOOD ]

$ ./testmusic /usr/local/share/heroes/mod/heroes01.xm 1024 22
Now playing
[ I hear the music => BAD ]

$ ./testmusic /usr/local/share/heroes/mod/heroes01.xm 1024 23
Now playing
[ I don't hear the music => GOOD ]

$ ./testmusic /usr/local/share/heroes/mod/heroes01.xm 2048 45
Now playing
[ I hear the music => BAD ]

$ ./testmusic /usr/local/share/heroes/mod/heroes01.xm 2048 46
Now playing
[ I don't hear the music => GOOD ]
#####

+++++ Comments
heroes01.xm comes from
http://prdownloads.sourceforge.net/heroes/heroes-sound-tracks-1.0.tar.bz2.
All the other modules I've tested show the same behaviour.

+++++ Analysis (using SDL_mixer source code):
It appears that the lowest value of chunksize for which the volume is taken
into account is equal to ms_per_step = (int) (((float)mixer->samples *
1000.0) / mixer->freq) [file music.c, function open_music()].
This also means that music->fade_steps [function Mix_FadeInMusicPos()] = 0
when and only when the volume isn't taken into account.
In this case, note that music_internal_volume() is never called from
music_mixer(), since (music_playing->fade_step++ < music_playing->fade_steps)
is never verified. This might explain the bug.

+++++ Testing environment:
- Mandrake Linux 9.1 i386
- SDL_mixer 1.2.4 (Mandrake package), 1.2.5 or CVS (both built from scratch)
- Athlon XP 1500+
- SB Live!

More details upon request. Thanks for your time.


--------

This is related to my previous message:
[SDL] Strange behaviour of Mix_FadeInMusic (1.2.5) on mods
http://www.libsdl.org/pipermail/sdl/2003-November/057749.html

+++++ Analysis (continued):
It appears that calling mikmod's Player_SetVolume() does nothing when called
before Player_Start() since pf [global variable initialized in mplayer.c] is
NULL then. This API seems a bit strange to me but well...
---
 music.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/music.c b/music.c
index 0a202971..b77b010a 100644
--- a/music.c
+++ b/music.c
@@ -135,6 +135,7 @@ static int native_midi_ok;
 static int ms_per_step;
 
 /* Local low-level functions prototypes */
+static void music_internal_initialize_volume(void);
 static void music_internal_volume(int volume);
 static int  music_internal_play(Mix_Music *music, double position);
 static int  music_internal_position(double position);
@@ -620,10 +621,8 @@ static int music_internal_play(Mix_Music *music, double position)
 	music_playing = music;
 
 	/* Set the initial volume */
-	if ( music->fading == MIX_FADING_IN ) {
-		music_internal_volume(0);
-	} else {
-		music_internal_volume(music_volume);
+	if ( music->type != MUS_MOD ) {
+		music_internal_initialize_volume();
 	}
 
 	/* Set up for playback */
@@ -641,6 +640,8 @@ static int music_internal_play(Mix_Music *music, double position)
 #ifdef MOD_MUSIC
 	    case MUS_MOD:
 		Player_Start(music->data.module);
+		/* Player_SetVolume() does nothing before Player_Start() */
+		music_internal_initialize_volume();
 		break;
 #endif
 #ifdef MID_MUSIC
@@ -788,6 +789,16 @@ int Mix_SetMusicPosition(double position)
 	return(retval);
 }
 
+/* Set the music's initial volume */
+static void music_internal_initialize_volume(void)
+{
+	if ( music_playing->fading == MIX_FADING_IN ) {
+		music_internal_volume(0);
+	} else {
+		music_internal_volume(music_volume);
+	}
+}
+
 /* Set the music volume */
 static void music_internal_volume(int volume)
 {