minimad.c

libman mp3解码库

/*
 * libmad - MPEG audio decoder library
 * Copyright (C) 2000-2004 Underbit Technologies, Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: minimad.c,v 1.4 2004/01/23 09:41:32 rob Exp $
 */

# include <stdio.h>
//# include <efs.h>
//# include <ls.h>
# include <string.h>

//# include <targets/lpc2148.h>
# include "mad.h"
//# include "debug.h"
//# include "lpc_io.h"
# include "midmad.h"

#define EmbeddedFile int
static unsigned char  mp3_stream_buf[512*3];
static EmbeddedFile  *mp3_file;

/*			  
 * This is perhaps the simplest example use of the MAD high-level API.
 * Standard input is mapped into memory via mmap(), then the high-level API
 * is invoked with three callbacks: input, output, and error. The output
 * callback converts MAD's high-resolution PCM samples to 16 bits, then
 * writes them to standard output in little-endian, stereo-interleaved
 * format.
 */
static int decode(unsigned char const *, unsigned long);

void abort(void)
{
}

void mp3_play(EmbeddedFile *file)
{ 
    mp3_file = file;
    decode((void *)mp3_stream_buf, sizeof(mp3_stream_buf)); 
}

/*
 * This is a private message structure. A generic pointer to this structure
 * is passed to each of the callback functions. Put here any data you need
 * to access from within the callbacks.
 */

struct buffer {
  unsigned char const *start;
  unsigned long length;
};

/*
 * This is the input callback. The purpose of this callback is to (re)fill
 * the stream buffer which is to be decoded. In this example, an entire file
 * has been mapped into memory, so we just call mad_stream_buffer() with the
 * address and length of the mapping. When this callback is called a second
 * time, we are finished decoding.
 */

static
enum mad_flow input(void *data, struct mad_stream *stream)
{
  struct buffer *buffer = data;
  unsigned int lb , rb = 0;

  if (!buffer->length)
    return MAD_FLOW_STOP;

  if (stream->this_frame && stream->next_frame)
  {
    rb = (unsigned int)(buffer->length) - 
         (unsigned int)(stream->next_frame - stream->buffer);

    memmove((void *)stream->buffer, (void *)stream->next_frame, rb);
    //lb = file_read(mp3_file, buffer->length - rb, (void *)(stream->buffer + rb));
  }
  else  
   ;// lb = file_read(mp3_file, buffer->length, (void *)buffer->start);

  if (lb == 0)
  {
    //wait_end_of_excerpt();bhj
    buffer->length = 0;
    return MAD_FLOW_STOP;
  }
  else 
    buffer->length = lb + rb;

  mad_stream_buffer(stream, buffer->start, buffer->length);
  //  buffer->length = 0;

  return MAD_FLOW_CONTINUE;
}

/*
 * The following utility routine performs simple rounding, clipping, and
 * scaling of MAD's high-resolution samples down to 16 bits. It does not
 * perform any dithering or noise shaping, which would be recommended to
 * obtain any exceptional audio quality. It is therefore not recommended to
 * use this routine if high-quality output is desired.
 */

static inline
signed int scale(mad_fixed_t sample)
{
  /* round */
  sample += (1L << (MAD_F_FRACBITS - 16));

  /* clip */
  if (sample >= MAD_F_ONE)
    sample = MAD_F_ONE - 1;
  else if (sample < -MAD_F_ONE)
    sample = -MAD_F_ONE;

  /* quantize */
  return sample >> (MAD_F_FRACBITS + 1 - 16);
}

/*
 * This is the output callback function. It is called after each frame of
 * MPEG audio data has been completely decoded. The purpose of this callback
 * is to output (or play) the decoded PCM audio.
 */

static
enum mad_flow output(void *data,
		     struct mad_header const *header,
		     struct mad_pcm *pcm)
{
  unsigned int nchannels, nsamples;
  unsigned int samplerate;
  //  unsigned int i;

  /* pcm->samplerate contains the sampling frequency */

  nchannels = pcm->channels;
  nsamples  = pcm->length;
  samplerate = pcm->samplerate;

  //TOGGLE_LIVE_LED0();

  return MAD_FLOW_CONTINUE;
}

/*
 * This is the error callback function. It is called whenever a decoding
 * error occurs. The error is indicated by stream->error; the list of
 * possible MAD_ERROR_* errors can be found in the mad.h (or stream.h)
 * header file.
 */

static
enum mad_flow error(void *data,
		    struct mad_stream *stream,
		    struct mad_frame *frame)
{
  // struct buffer *buffer = data;

  // printf("decoding error 0x%04x (%s) at byte offset %u\n",
  //	  stream->error, mad_stream_errorstr(stream),
  // 	  stream->this_frame - buffer->start);

  /* return MAD_FLOW_BREAK here to stop decoding (and propagate an error) */

  return MAD_FLOW_CONTINUE;
}

/*
 * This is the function called by main() above to perform all the decoding.
 * It instantiates a decoder object and configures it with the input,
 * output, and error callback functions above. A single call to
 * mad_decoder_run() continues until a callback function returns
 * MAD_FLOW_STOP (to stop decoding) or MAD_FLOW_BREAK (to stop decoding and
 * signal an error).
 */

static
int decode(unsigned char const *start, unsigned long length)
{
  struct buffer buffer;
  struct mad_decoder decoder;
  int result;

  /* initialize our private message structure */

  buffer.start  = start;
  buffer.length = length;

  /* configure input, output, and error functions */

  mad_decoder_init(&decoder, 
                  &buffer,
		   input, 
                   0 /* header */, 
                   0 /* filter */,
                   output,
		   error, 
                   0 /* message */);

  /* start decoding */

  result = mad_decoder_run(&decoder, MAD_DECODER_MODE_SYNC);

  /* release the decoder */

  mad_decoder_finish(&decoder);

  return result;
}