在Linux下基于libmad库的音乐播放器

#include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <sys/stat.h> #include <sys/mman.h> #include <sys/types.h> #include <fcntl.h> #include <linux/soundcard.h> #include <sys/ioctl.h> #include <string.h> #include "mad.h" #include "main.h" int soundfd; int mp3_fd[2][3]; struct buffer { unsigned char const *start; unsigned long length; }; /*int decode(unsigned char const *, unsigned long); void set_dsp(void); int play_control(int next, int pro); int play(int flag); int creat_soundfd(void); int writedsp(int c);*/ /*int main(int argc, const char *argv[]) { //creat_soundfd(); set_dsp(); play(1); play_control(0, 1); return 0; }*/ int play(int flag) { struct stat file; void *address; switch(flag) { case 0: if((mp3_fd[0][0] = open("1.mp3", O_RDONLY)) < 0) { perror("open 1"); exit(1); } fstat(mp3_fd[0][0], &file); address = mmap(0, file.st_size, PROT_READ, MAP_SHARED,mp3_fd[0][0], 0); mp3_fd[1][0] = 1; decode(address, file.st_size); if(munmap(address, file.st_size) == -1) perror("mumap"); close(mp3_fd[0][0]); mp3_fd[1][0] = 0; case 1: if((mp3_fd[0][1] = open("2.mp3", O_RDONLY)) < 0) { perror("open 1"); exit(1); } fstat(mp3_fd[0][1], &file); address = mmap(0, file.st_size, PROT_READ, MAP_SHARED,mp3_fd[0][1], 0); mp3_fd[1][1] = 1; decode(address, file.st_size); if(munmap(address, file.st_size) == -1) perror("mumap"); close(mp3_fd[0][1]); mp3_fd[1][1] = 0; case 2: if((mp3_fd[0][2] = open("3.mp3", O_RDONLY)) < 0) { perror("open 1"); exit(1); } fstat(mp3_fd[0][2], &file); address = mmap(0, file.st_size, PROT_READ, MAP_SHARED,mp3_fd[0][2], 0); mp3_fd[1][2] = 1; decode(address, file.st_size); if(munmap(address, file.st_size) == -1) perror("mumap"); close(mp3_fd[0][2]); mp3_fd[1][2] = 0; } return 0; } int play_control(int next, int pro) { int i = 0; while(i<3) { if(i == 2) { if(mp3_fd[1][2] == 1 && mp3_fd[1][0] == 0) break; } else { if(mp3_fd[1][i] == 1 && mp3_fd[1][i+1] == 0) break; } i++; } if(next >= 0) { if(i == 2) play(0); else play(i+1); } if(pro >= 0) { if(i == 0) play(2); else play(i - 1); } return 0; } int creat_soundfd(void) { if((mp3_fd[0][0] = open("1.mp3", O_RDONLY)) < 0) { perror("open 1"); exit(1); } if((mp3_fd[0][1] = open("2.mp3", O_RDONLY)) < 0) { perror("open 2"); exit(1); } if((mp3_fd[0][2] = open("3.mp3", O_RDONLY)) < 0) { perror("open 3"); exit(1); } return 0; } int writedsp(int c) { return write(soundfd, (char *)&c, 1); } void set_dsp(void) { int format = AFMT_S16_LE; int channels = 2; unsigned int rate = 44100; if((soundfd = open("/dev/dsp", O_RDWR)) < 0) { printf("don't open the dsp\n"); exit(1); } ioctl(soundfd, SNDCTL_DSP_SETFMT, &format); ioctl(soundfd, SNDCTL_DSP_SYNC, 0); ioctl(soundfd, SNDCTL_DSP_CHANNELS, &channels); ioctl(soundfd, SNDCTL_DSP_SPEED, &rate); } /* * 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; //unsigned int rate = 44100; /* pcm->samplerate contains the sampling frequency */ //rate = pcm->samplerate; nchannels = pcm->channels; nsamples = pcm->length; left_ch = pcm->samples[0]; right_ch = pcm->samples[1]; //if(rate != prerate) //{ //ioctl(soundfd, SNDCTL_DSP_SPEED, &rate); //prerate = rate; //} while (nsamples--) { signed int sample; /* output sample(s) in 16-bit signed little-endian PCM */ sample = scale(*left_ch++); writedsp((sample >> 0) & 0xff); writedsp((sample >> 8) & 0xff); if (nchannels == 2) { sample = scale(*right_ch++); writedsp((sample >> 0) & 0xff); writedsp((sample >> 8) & 0xff); } } return MAD_FLOW_CONTINUE; } 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). */ 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; }