Date: 10 Jun 2003 15:30:59 -0400

From: Mike Shal
Subject: [SDL] Bug in SDL_wave.c?

Hey everyone, I'm not sure if this is a bug in SDL, or if I just have
incorrect WAV files.  The problem I'm having is loading multiple
concatenated WAVs from SDL_LoadWAV_RW.  Some WAV files put comments at
the end of the file (which may be bad form), and SDL doesn't skip past
them when reading from the RWops.  So the next WAV I try to load will
start at the comment section of the previous WAV, which obviously
doesn't work.  If anyone else is having this problem, one quick fix you
can do is run sox on the bad WAVs, which strips out all of the comment
sections.
Eg:

$ sox sound.wav tmp.wav
$ mv -f tmp.wav sound.wav

The other fix is to patch SDL_wave.c, which is included with this email.
(Assuming I made the patch correctly :).  All it does is calculate how
much remaining space there is in the WAV file after the data chunk, and
does SDL_RWseek to skip it.  I don't think it should interfere with
anything else, but if someone could check it that would be nice :).  If
the bug is really with SDL and not with my WAVs, can someone work this
into the next version of SDL? Thanks,

-Mike Shal

--HG--
extra : convert_revision : svn%3Ac70aab31-4412-0410-b14c-859654838e24/trunk%401263

src/audio/SDL_wave.c

@@ -418,8 +418,9 @@ SDL_AudioSpec * SDL_LoadWAV_RW (SDL_RWops *src, int freesrc,
 
 	/* WAV magic header */
 	Uint32 RIFFchunk;
-	Uint32 wavelen;
+	Uint32 wavelen = 0;
 	Uint32 WAVEmagic;
+	Uint32 headerDiff = 0;
 
 	/* FMT chunk */
 	WaveFMT *format = NULL;
@@ -446,6 +447,7 @@ SDL_AudioSpec * SDL_LoadWAV_RW (SDL_RWops *src, int freesrc,
 		was_error = 1;
 		goto done;
 	}
+	headerDiff += sizeof(Uint32); // for WAVE
 
 	/* Read the audio data format chunk */
 	chunk.data = NULL;
@@ -458,6 +460,8 @@ SDL_AudioSpec * SDL_LoadWAV_RW (SDL_RWops *src, int freesrc,
 			was_error = 1;
 			goto done;
 		}
+		// 2 Uint32's for chunk header+len, plus the lenread
+		headerDiff += lenread + 2 * sizeof(Uint32);
 	} while ( (chunk.magic == FACT) || (chunk.magic == LIST) );
 
 	/* Decode the audio data format */
@@ -535,7 +539,9 @@ SDL_AudioSpec * SDL_LoadWAV_RW (SDL_RWops *src, int freesrc,
 		}
 		*audio_len = lenread;
 		*audio_buf = chunk.data;
+		if(chunk.magic != DATA) headerDiff += lenread + 2 * sizeof(Uint32);
 	} while ( chunk.magic != DATA );
+	headerDiff += 2 * sizeof(Uint32); // for the data chunk and len
 
 	if ( MS_ADPCM_encoded ) {
 		if ( MS_ADPCM_decode(audio_buf, audio_len) < 0 ) {
@@ -561,6 +567,10 @@ done:
 	if ( freesrc && src ) {
 		SDL_RWclose(src);
 	}
+	else {
+		// seek to the end of the file (given by the RIFF chunk)
+		SDL_RWseek(src, wavelen - chunk.length - headerDiff, SEEK_CUR);
+	}
 	if ( was_error ) {
 		spec = NULL;
 	}