From d35747a40c7dea12de95f78a4f283a45ef687597 Mon Sep 17 00:00:00 2001 From: Warren Dukes Date: Mon, 23 Feb 2004 23:41:20 +0000 Subject: import from SF CVS git-svn-id: https://svn.musicpd.org/mpd/trunk@1 09075e82-0dd4-0310-85a5-a0d7c8717e4f --- src/libmad/minimad.c | 222 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 222 insertions(+) create mode 100644 src/libmad/minimad.c (limited to 'src/libmad/minimad.c') diff --git a/src/libmad/minimad.c b/src/libmad/minimad.c new file mode 100644 index 000000000..bb4f7154a --- /dev/null +++ b/src/libmad/minimad.c @@ -0,0 +1,222 @@ +/* + * libmad - MPEG audio decoder library + * Copyright (C) 2000-2003 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 1.1 2003/08/14 03:57:13 shank Exp $ + */ + +# include +# include +# include +# include + +# 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 + * libmad/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; +} -- cgit v1.2.3