Chris@0: /*
Chris@0:  * libmad - MPEG audio decoder library
Chris@0:  * Copyright (C) 2000-2004 Underbit Technologies, Inc.
Chris@0:  *
Chris@0:  * This program is free software; you can redistribute it and/or modify
Chris@0:  * it under the terms of the GNU General Public License as published by
Chris@0:  * the Free Software Foundation; either version 2 of the License, or
Chris@0:  * (at your option) any later version.
Chris@0:  *
Chris@0:  * This program is distributed in the hope that it will be useful,
Chris@0:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
Chris@0:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
Chris@0:  * GNU General Public License for more details.
Chris@0:  *
Chris@0:  * You should have received a copy of the GNU General Public License
Chris@0:  * along with this program; if not, write to the Free Software
Chris@0:  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
Chris@0:  *
Chris@0:  * $Id: minimad.c,v 1.4 2004/01/23 09:41:32 rob Exp $
Chris@0:  */
Chris@0: 
Chris@0: # include <stdio.h>
Chris@0: # include <unistd.h>
Chris@0: # include <sys/stat.h>
Chris@0: # include <sys/mman.h>
Chris@0: 
Chris@0: # include "mad.h"
Chris@0: 
Chris@0: /*
Chris@0:  * This is perhaps the simplest example use of the MAD high-level API.
Chris@0:  * Standard input is mapped into memory via mmap(), then the high-level API
Chris@0:  * is invoked with three callbacks: input, output, and error. The output
Chris@0:  * callback converts MAD's high-resolution PCM samples to 16 bits, then
Chris@0:  * writes them to standard output in little-endian, stereo-interleaved
Chris@0:  * format.
Chris@0:  */
Chris@0: 
Chris@0: static int decode(unsigned char const *, unsigned long);
Chris@0: 
Chris@0: int main(int argc, char *argv[])
Chris@0: {
Chris@0:   struct stat stat;
Chris@0:   void *fdm;
Chris@0: 
Chris@0:   if (argc != 1)
Chris@0:     return 1;
Chris@0: 
Chris@0:   if (fstat(STDIN_FILENO, &stat) == -1 ||
Chris@0:       stat.st_size == 0)
Chris@0:     return 2;
Chris@0: 
Chris@0:   fdm = mmap(0, stat.st_size, PROT_READ, MAP_SHARED, STDIN_FILENO, 0);
Chris@0:   if (fdm == MAP_FAILED)
Chris@0:     return 3;
Chris@0: 
Chris@0:   decode(fdm, stat.st_size);
Chris@0: 
Chris@0:   if (munmap(fdm, stat.st_size) == -1)
Chris@0:     return 4;
Chris@0: 
Chris@0:   return 0;
Chris@0: }
Chris@0: 
Chris@0: /*
Chris@0:  * This is a private message structure. A generic pointer to this structure
Chris@0:  * is passed to each of the callback functions. Put here any data you need
Chris@0:  * to access from within the callbacks.
Chris@0:  */
Chris@0: 
Chris@0: struct buffer {
Chris@0:   unsigned char const *start;
Chris@0:   unsigned long length;
Chris@0: };
Chris@0: 
Chris@0: /*
Chris@0:  * This is the input callback. The purpose of this callback is to (re)fill
Chris@0:  * the stream buffer which is to be decoded. In this example, an entire file
Chris@0:  * has been mapped into memory, so we just call mad_stream_buffer() with the
Chris@0:  * address and length of the mapping. When this callback is called a second
Chris@0:  * time, we are finished decoding.
Chris@0:  */
Chris@0: 
Chris@0: static
Chris@0: enum mad_flow input(void *data,
Chris@0: 		    struct mad_stream *stream)
Chris@0: {
Chris@0:   struct buffer *buffer = data;
Chris@0: 
Chris@0:   if (!buffer->length)
Chris@0:     return MAD_FLOW_STOP;
Chris@0: 
Chris@0:   mad_stream_buffer(stream, buffer->start, buffer->length);
Chris@0: 
Chris@0:   buffer->length = 0;
Chris@0: 
Chris@0:   return MAD_FLOW_CONTINUE;
Chris@0: }
Chris@0: 
Chris@0: /*
Chris@0:  * The following utility routine performs simple rounding, clipping, and
Chris@0:  * scaling of MAD's high-resolution samples down to 16 bits. It does not
Chris@0:  * perform any dithering or noise shaping, which would be recommended to
Chris@0:  * obtain any exceptional audio quality. It is therefore not recommended to
Chris@0:  * use this routine if high-quality output is desired.
Chris@0:  */
Chris@0: 
Chris@0: static inline
Chris@0: signed int scale(mad_fixed_t sample)
Chris@0: {
Chris@0:   /* round */
Chris@0:   sample += (1L << (MAD_F_FRACBITS - 16));
Chris@0: 
Chris@0:   /* clip */
Chris@0:   if (sample >= MAD_F_ONE)
Chris@0:     sample = MAD_F_ONE - 1;
Chris@0:   else if (sample < -MAD_F_ONE)
Chris@0:     sample = -MAD_F_ONE;
Chris@0: 
Chris@0:   /* quantize */
Chris@0:   return sample >> (MAD_F_FRACBITS + 1 - 16);
Chris@0: }
Chris@0: 
Chris@0: /*
Chris@0:  * This is the output callback function. It is called after each frame of
Chris@0:  * MPEG audio data has been completely decoded. The purpose of this callback
Chris@0:  * is to output (or play) the decoded PCM audio.
Chris@0:  */
Chris@0: 
Chris@0: static
Chris@0: enum mad_flow output(void *data,
Chris@0: 		     struct mad_header const *header,
Chris@0: 		     struct mad_pcm *pcm)
Chris@0: {
Chris@0:   unsigned int nchannels, nsamples;
Chris@0:   mad_fixed_t const *left_ch, *right_ch;
Chris@0: 
Chris@0:   /* pcm->samplerate contains the sampling frequency */
Chris@0: 
Chris@0:   nchannels = pcm->channels;
Chris@0:   nsamples  = pcm->length;
Chris@0:   left_ch   = pcm->samples[0];
Chris@0:   right_ch  = pcm->samples[1];
Chris@0: 
Chris@0:   while (nsamples--) {
Chris@0:     signed int sample;
Chris@0: 
Chris@0:     /* output sample(s) in 16-bit signed little-endian PCM */
Chris@0: 
Chris@0:     sample = scale(*left_ch++);
Chris@0:     putchar((sample >> 0) & 0xff);
Chris@0:     putchar((sample >> 8) & 0xff);
Chris@0: 
Chris@0:     if (nchannels == 2) {
Chris@0:       sample = scale(*right_ch++);
Chris@0:       putchar((sample >> 0) & 0xff);
Chris@0:       putchar((sample >> 8) & 0xff);
Chris@0:     }
Chris@0:   }
Chris@0: 
Chris@0:   return MAD_FLOW_CONTINUE;
Chris@0: }
Chris@0: 
Chris@0: /*
Chris@0:  * This is the error callback function. It is called whenever a decoding
Chris@0:  * error occurs. The error is indicated by stream->error; the list of
Chris@0:  * possible MAD_ERROR_* errors can be found in the mad.h (or stream.h)
Chris@0:  * header file.
Chris@0:  */
Chris@0: 
Chris@0: static
Chris@0: enum mad_flow error(void *data,
Chris@0: 		    struct mad_stream *stream,
Chris@0: 		    struct mad_frame *frame)
Chris@0: {
Chris@0:   struct buffer *buffer = data;
Chris@0: 
Chris@0:   fprintf(stderr, "decoding error 0x%04x (%s) at byte offset %u\n",
Chris@0: 	  stream->error, mad_stream_errorstr(stream),
Chris@0: 	  stream->this_frame - buffer->start);
Chris@0: 
Chris@0:   /* return MAD_FLOW_BREAK here to stop decoding (and propagate an error) */
Chris@0: 
Chris@0:   return MAD_FLOW_CONTINUE;
Chris@0: }
Chris@0: 
Chris@0: /*
Chris@0:  * This is the function called by main() above to perform all the decoding.
Chris@0:  * It instantiates a decoder object and configures it with the input,
Chris@0:  * output, and error callback functions above. A single call to
Chris@0:  * mad_decoder_run() continues until a callback function returns
Chris@0:  * MAD_FLOW_STOP (to stop decoding) or MAD_FLOW_BREAK (to stop decoding and
Chris@0:  * signal an error).
Chris@0:  */
Chris@0: 
Chris@0: static
Chris@0: int decode(unsigned char const *start, unsigned long length)
Chris@0: {
Chris@0:   struct buffer buffer;
Chris@0:   struct mad_decoder decoder;
Chris@0:   int result;
Chris@0: 
Chris@0:   /* initialize our private message structure */
Chris@0: 
Chris@0:   buffer.start  = start;
Chris@0:   buffer.length = length;
Chris@0: 
Chris@0:   /* configure input, output, and error functions */
Chris@0: 
Chris@0:   mad_decoder_init(&decoder, &buffer,
Chris@0: 		   input, 0 /* header */, 0 /* filter */, output,
Chris@0: 		   error, 0 /* message */);
Chris@0: 
Chris@0:   /* start decoding */
Chris@0: 
Chris@0:   result = mad_decoder_run(&decoder, MAD_DECODER_MODE_SYNC);
Chris@0: 
Chris@0:   /* release the decoder */
Chris@0: 
Chris@0:   mad_decoder_finish(&decoder);
Chris@0: 
Chris@0:   return result;
Chris@0: }