music_mad.c
author Sam Lantinga <slouken@libsdl.org>
Fri, 13 Jan 2012 03:15:19 -0500
changeset 561 87bdb4c81c0b
parent 542 3de4970b36d4
child 600 413430798384
permissions -rw-r--r--
Fixed memory crash loading Ogg Vorbis files on Windows
The pointer to the audio data could come from SDL_LoadWAV_RW() or from our other loaders, and we need to use the correct free() to release the memory. So we'll just use the SDL memory functions for consistency.
This pretty much only matters on Windows where we can't guarantee a certain C runtime so we provide our own malloc() and friends.
     1 /*
     2   SDL_mixer:  An audio mixer library based on the SDL library
     3   Copyright (C) 1997-2012 Sam Lantinga <slouken@libsdl.org>
     4 
     5   This software is provided 'as-is', without any express or implied
     6   warranty.  In no event will the authors be held liable for any damages
     7   arising from the use of this software.
     8 
     9   Permission is granted to anyone to use this software for any purpose,
    10   including commercial applications, and to alter it and redistribute it
    11   freely, subject to the following restrictions:
    12 
    13   1. The origin of this software must not be misrepresented; you must not
    14      claim that you wrote the original software. If you use this software
    15      in a product, an acknowledgment in the product documentation would be
    16      appreciated but is not required.
    17   2. Altered source versions must be plainly marked as such, and must not be
    18      misrepresented as being the original software.
    19   3. This notice may not be removed or altered from any source distribution.
    20 */
    21 
    22 #ifdef MP3_MAD_MUSIC
    23 
    24 #include <string.h>
    25 
    26 #include "music_mad.h"
    27 
    28 mad_data *
    29 mad_openFileRW(SDL_RWops *rw, SDL_AudioSpec *mixer, int freerw)
    30 {
    31   mad_data *mp3_mad;
    32 
    33   mp3_mad = (mad_data *)SDL_malloc(sizeof(mad_data));
    34   if (mp3_mad) {
    35 	mp3_mad->rw = rw;
    36 	mp3_mad->freerw = freerw;
    37 	mad_stream_init(&mp3_mad->stream);
    38 	mad_frame_init(&mp3_mad->frame);
    39 	mad_synth_init(&mp3_mad->synth);
    40 	mp3_mad->frames_read = 0;
    41 	mad_timer_reset(&mp3_mad->next_frame_start);
    42 	mp3_mad->volume = MIX_MAX_VOLUME;
    43 	mp3_mad->status = 0;
    44 	mp3_mad->output_begin = 0;
    45 	mp3_mad->output_end = 0;
    46 	mp3_mad->mixer = *mixer;
    47   }
    48   return mp3_mad;
    49 }
    50 
    51 void
    52 mad_closeFile(mad_data *mp3_mad)
    53 {
    54   mad_stream_finish(&mp3_mad->stream);
    55   mad_frame_finish(&mp3_mad->frame);
    56   mad_synth_finish(&mp3_mad->synth);
    57 
    58   if (mp3_mad->freerw) {
    59 	SDL_RWclose(mp3_mad->rw);
    60   }
    61   SDL_free(mp3_mad);
    62 }
    63 
    64 /* Starts the playback. */
    65 void
    66 mad_start(mad_data *mp3_mad) {
    67   mp3_mad->status |= MS_playing;
    68 }
    69 
    70 /* Stops the playback. */
    71 void 
    72 mad_stop(mad_data *mp3_mad) {
    73   mp3_mad->status &= ~MS_playing;
    74 }
    75 
    76 /* Returns true if the playing is engaged, false otherwise. */
    77 int
    78 mad_isPlaying(mad_data *mp3_mad) {
    79   return ((mp3_mad->status & MS_playing) != 0);
    80 }
    81 
    82 /* Reads the next frame from the file.  Returns true on success or
    83    false on failure. */
    84 static int
    85 read_next_frame(mad_data *mp3_mad) {
    86   if (mp3_mad->stream.buffer == NULL || 
    87 	  mp3_mad->stream.error == MAD_ERROR_BUFLEN) {
    88 	size_t read_size;
    89 	size_t remaining;
    90 	unsigned char *read_start;
    91 	
    92 	/* There might be some bytes in the buffer left over from last
    93 	   time.  If so, move them down and read more bytes following
    94 	   them. */
    95 	if (mp3_mad->stream.next_frame != NULL) {
    96 	  remaining = mp3_mad->stream.bufend - mp3_mad->stream.next_frame;
    97 	  memmove(mp3_mad->input_buffer, mp3_mad->stream.next_frame, remaining);
    98 	  read_start = mp3_mad->input_buffer + remaining;
    99 	  read_size = MAD_INPUT_BUFFER_SIZE - remaining;
   100 	  
   101 	} else {
   102 	  read_size = MAD_INPUT_BUFFER_SIZE;
   103 	  read_start = mp3_mad->input_buffer;
   104 	  remaining = 0;
   105 	}
   106 
   107 	/* Now read additional bytes from the input file. */
   108 	read_size = SDL_RWread(mp3_mad->rw, read_start, 1, read_size);
   109 	
   110 	if (read_size <= 0) {
   111 	  if ((mp3_mad->status & (MS_input_eof | MS_input_error)) == 0) {
   112 		if (read_size == 0) {
   113 		  mp3_mad->status |= MS_input_eof;
   114 		} else {
   115 		  mp3_mad->status |= MS_input_error;
   116 		}
   117 		
   118 		/* At the end of the file, we must stuff MAD_BUFFER_GUARD
   119 		   number of 0 bytes. */
   120 		memset(read_start + read_size, 0, MAD_BUFFER_GUARD);
   121 		read_size += MAD_BUFFER_GUARD;
   122 	  }
   123 	}
   124 	
   125 	/* Now feed those bytes into the libmad stream. */
   126 	mad_stream_buffer(&mp3_mad->stream, mp3_mad->input_buffer,
   127 					  read_size + remaining);
   128 	mp3_mad->stream.error = MAD_ERROR_NONE;
   129   }
   130   
   131   /* Now ask libmad to extract a frame from the data we just put in
   132 	 its buffer. */
   133   if (mad_frame_decode(&mp3_mad->frame, &mp3_mad->stream)) {
   134 	if (MAD_RECOVERABLE(mp3_mad->stream.error)) {
   135 	  return 0;
   136 	  
   137 	} else if (mp3_mad->stream.error == MAD_ERROR_BUFLEN) {
   138 	  return 0;
   139 	  
   140 	} else {
   141 	  mp3_mad->status |= MS_decode_error;
   142 	  return 0;
   143 	}
   144   }
   145   
   146   mp3_mad->frames_read++;
   147   mad_timer_add(&mp3_mad->next_frame_start, mp3_mad->frame.header.duration);
   148 
   149   return 1;
   150 }
   151 
   152 /* Scale a MAD sample to 16 bits for output. */
   153 static signed int
   154 scale(mad_fixed_t sample) {
   155   /* round */
   156   sample += (1L << (MAD_F_FRACBITS - 16));
   157 
   158   /* clip */
   159   if (sample >= MAD_F_ONE)
   160     sample = MAD_F_ONE - 1;
   161   else if (sample < -MAD_F_ONE)
   162     sample = -MAD_F_ONE;
   163 
   164   /* quantize */
   165   return sample >> (MAD_F_FRACBITS + 1 - 16);
   166 }
   167 
   168 /* Once the frame has been read, copies its samples into the output
   169    buffer. */
   170 static void
   171 decode_frame(mad_data *mp3_mad) {
   172   struct mad_pcm *pcm;
   173   unsigned int nchannels, nsamples;
   174   mad_fixed_t const *left_ch, *right_ch;
   175   unsigned char *out;
   176   int ret;
   177 
   178   mad_synth_frame(&mp3_mad->synth, &mp3_mad->frame);
   179   pcm = &mp3_mad->synth.pcm;
   180   out = mp3_mad->output_buffer + mp3_mad->output_end;
   181 
   182   if ((mp3_mad->status & MS_cvt_decoded) == 0) {
   183 	mp3_mad->status |= MS_cvt_decoded;
   184 
   185 	/* The first frame determines some key properties of the stream.
   186 	   In particular, it tells us enough to set up the convert
   187 	   structure now. */
   188 	SDL_BuildAudioCVT(&mp3_mad->cvt, AUDIO_S16, pcm->channels, mp3_mad->frame.header.samplerate, mp3_mad->mixer.format, mp3_mad->mixer.channels, mp3_mad->mixer.freq);
   189   }
   190 
   191   /* pcm->samplerate contains the sampling frequency */
   192 
   193   nchannels = pcm->channels;
   194   nsamples  = pcm->length;
   195   left_ch   = pcm->samples[0];
   196   right_ch  = pcm->samples[1];
   197 
   198   while (nsamples--) {
   199     signed int sample;
   200 
   201     /* output sample(s) in 16-bit signed little-endian PCM */
   202 
   203     sample = scale(*left_ch++);
   204     *out++ = ((sample >> 0) & 0xff);
   205     *out++ = ((sample >> 8) & 0xff);
   206 
   207     if (nchannels == 2) {
   208       sample = scale(*right_ch++);
   209       *out++ = ((sample >> 0) & 0xff);
   210       *out++ = ((sample >> 8) & 0xff);
   211     }
   212   }
   213 
   214   mp3_mad->output_end = out - mp3_mad->output_buffer;
   215   /*assert(mp3_mad->output_end <= MAD_OUTPUT_BUFFER_SIZE);*/
   216 }
   217 
   218 int
   219 mad_getSamples(mad_data *mp3_mad, Uint8 *stream, int len) {
   220   int bytes_remaining;
   221   int num_bytes;
   222   Uint8 *out;
   223 
   224   if ((mp3_mad->status & MS_playing) == 0) {
   225 	/* We're not supposed to be playing, so send silence instead. */
   226 	memset(stream, 0, len);
   227 	return;
   228   }
   229 
   230   out = stream;
   231   bytes_remaining = len;
   232   while (bytes_remaining > 0) {
   233 	if (mp3_mad->output_end == mp3_mad->output_begin) {
   234 	  /* We need to get a new frame. */
   235 	  mp3_mad->output_begin = 0;
   236 	  mp3_mad->output_end = 0;
   237 	  if (!read_next_frame(mp3_mad)) {
   238 		if ((mp3_mad->status & MS_error_flags) != 0) {
   239 		  /* Couldn't read a frame; either an error condition or
   240 			 end-of-file.  Stop. */
   241 		  memset(out, 0, bytes_remaining);
   242 		  mp3_mad->status &= ~MS_playing;
   243 		  return bytes_remaining;
   244 		}
   245 	  } else {
   246 		decode_frame(mp3_mad);
   247 
   248 		/* Now convert the frame data to the appropriate format for
   249 		   output. */
   250 		mp3_mad->cvt.buf = mp3_mad->output_buffer;
   251 		mp3_mad->cvt.len = mp3_mad->output_end;
   252 		
   253 		mp3_mad->output_end = (int)(mp3_mad->output_end * mp3_mad->cvt.len_ratio);
   254 		/*assert(mp3_mad->output_end <= MAD_OUTPUT_BUFFER_SIZE);*/
   255 		SDL_ConvertAudio(&mp3_mad->cvt);
   256 	  }
   257 	}
   258 
   259 	num_bytes = mp3_mad->output_end - mp3_mad->output_begin;
   260 	if (bytes_remaining < num_bytes) {
   261 	  num_bytes = bytes_remaining;
   262 	}
   263 
   264 	if (mp3_mad->volume == MIX_MAX_VOLUME) {
   265 	  memcpy(out, mp3_mad->output_buffer + mp3_mad->output_begin, num_bytes);
   266 	} else {
   267 	  SDL_MixAudio(out, mp3_mad->output_buffer + mp3_mad->output_begin,
   268 				   num_bytes, mp3_mad->volume);
   269 	}
   270 	out += num_bytes;
   271 	mp3_mad->output_begin += num_bytes;
   272 	bytes_remaining -= num_bytes;
   273   }
   274   return 0;
   275 }
   276 
   277 void
   278 mad_seek(mad_data *mp3_mad, double position) {
   279   mad_timer_t target;
   280   int int_part;
   281 
   282   int_part = (int)position;
   283   mad_timer_set(&target, int_part, 
   284 				(int)((position - int_part) * 1000000), 1000000);
   285 
   286   if (mad_timer_compare(mp3_mad->next_frame_start, target) > 0) {
   287 	/* In order to seek backwards in a VBR file, we have to rewind and
   288 	   start again from the beginning.  This isn't necessary if the
   289 	   file happens to be CBR, of course; in that case we could seek
   290 	   directly to the frame we want.  But I leave that little
   291 	   optimization for the future developer who discovers she really
   292 	   needs it. */
   293 	mp3_mad->frames_read = 0;
   294 	mad_timer_reset(&mp3_mad->next_frame_start);
   295 	mp3_mad->status &= ~MS_error_flags;
   296 	mp3_mad->output_begin = 0;
   297 	mp3_mad->output_end = 0;
   298 
   299 	SDL_RWseek(mp3_mad->rw, 0, RW_SEEK_SET);
   300   }
   301 
   302   /* Now we have to skip frames until we come to the right one.
   303 	 Again, only truly necessary if the file is VBR. */
   304   while (mad_timer_compare(mp3_mad->next_frame_start, target) < 0) {
   305 	if (!read_next_frame(mp3_mad)) {
   306 	  if ((mp3_mad->status & MS_error_flags) != 0) {
   307 		/* Couldn't read a frame; either an error condition or
   308 		   end-of-file.  Stop. */
   309 		mp3_mad->status &= ~MS_playing;
   310 		return;
   311 	  }
   312 	}
   313   }
   314 
   315   /* Here we are, at the beginning of the frame that contains the
   316 	 target time.  Ehh, I say that's close enough.  If we wanted to,
   317 	 we could get more precise by decoding the frame now and counting
   318 	 the appropriate number of samples out of it. */
   319 }
   320 
   321 void
   322 mad_setVolume(mad_data *mp3_mad, int volume) {
   323   mp3_mad->volume = volume;
   324 }
   325 
   326 
   327 #endif  /* MP3_MAD_MUSIC */