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Diffstat (limited to 'src/libmad/minimad.c')
-rw-r--r-- | src/libmad/minimad.c | 222 |
1 files changed, 0 insertions, 222 deletions
diff --git a/src/libmad/minimad.c b/src/libmad/minimad.c index ac412ae44..e69de29bb 100644 --- a/src/libmad/minimad.c +++ b/src/libmad/minimad.c @@ -1,222 +0,0 @@ -/* - * 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 <unistd.h> -# include <sys/stat.h> -# include <sys/mman.h> - -# include "mad.h" - -/* - * 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); - -int main(int argc, char *argv[]) -{ - struct stat stat; - void *fdm; - - if (argc != 1) - return 1; - - if (fstat(STDIN_FILENO, &stat) == -1 || - stat.st_size == 0) - return 2; - - fdm = mmap(0, stat.st_size, PROT_READ, MAP_SHARED, STDIN_FILENO, 0); - if (fdm == MAP_FAILED) - return 3; - - decode(fdm, stat.st_size); - - if (munmap(fdm, stat.st_size) == -1) - return 4; - - return 0; -} - -/* - * 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; - - if (!buffer->length) - return MAD_FLOW_STOP; - - 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; - mad_fixed_t const *left_ch, *right_ch; - - /* pcm->samplerate contains the sampling frequency */ - - nchannels = pcm->channels; - nsamples = pcm->length; - left_ch = pcm->samples[0]; - right_ch = pcm->samples[1]; - - while (nsamples--) { - signed int sample; - - /* output sample(s) in 16-bit signed little-endian PCM */ - - sample = scale(*left_ch++); - putchar((sample >> 0) & 0xff); - putchar((sample >> 8) & 0xff); - - if (nchannels == 2) { - sample = scale(*right_ch++); - putchar((sample >> 0) & 0xff); - putchar((sample >> 8) & 0xff); - } - } - - 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; - - fprintf(stderr, "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; -} |