124 lines
2.3 KiB
C
124 lines
2.3 KiB
C
#include <mpg123.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "mp3.h"
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#include "playback.h"
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static size_t* buffSize;
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static mpg123_handle *mh = NULL;
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static uint32_t rate;
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static uint8_t channels;
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static int initMp3(const char* file);
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static uint32_t rateMp3(void);
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static uint8_t channelMp3(void);
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static uint64_t decodeMp3(void* buffer);
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static void exitMp3(void);
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/**
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* Set decoder parameters for MP3.
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*
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* \param decoder Structure to store parameters.
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*/
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void setMp3(struct decoder_fn* decoder)
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{
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decoder->init = &initMp3;
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decoder->rate = &rateMp3;
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decoder->channels = &channelMp3;
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/*
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* buffSize changes depending on input file. So we set buffSize later when
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* decoder is initialised.
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*/
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buffSize = &(decoder->buffSize);
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decoder->decode = &decodeMp3;
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decoder->exit = &exitMp3;
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}
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/**
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* Initialise MP3 decoder.
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*
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* \param file Location of MP3 file to play.
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* \return 0 on success, else failure.
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*/
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int initMp3(const char* file)
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{
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int err = 0;
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int encoding = 0;
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if((err = mpg123_init()) != MPG123_OK)
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return err;
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if((mh = mpg123_new(NULL, &err)) == NULL)
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{
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printf("Error: %s\n", mpg123_plain_strerror(err));
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return err;
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}
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if(mpg123_open(mh, file) != MPG123_OK ||
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mpg123_getformat(mh, (long *) &rate, (int *) &channels, &encoding) != MPG123_OK)
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{
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printf("Trouble with mpg123: %s\n", mpg123_strerror(mh));
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return -1;
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}
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/*
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* Ensure that this output format will not change (it might, when we allow
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* it).
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*/
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mpg123_format_none(mh);
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mpg123_format(mh, rate, channels, encoding);
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/*
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* Buffer could be almost any size here, mpg123_outblock() is just some
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* recommendation. The size should be a multiple of the PCM frame size.
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*/
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*buffSize = mpg123_outblock(mh) * 16;
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return 0;
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}
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/**
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* Get sampling rate of MP3 file.
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*
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* \return Sampling rate.
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*/
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uint32_t rateMp3(void)
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{
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return rate;
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}
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/**
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* Get number of channels of MP3 file.
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*
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* \return Number of channels for opened file.
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*/
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uint8_t channelMp3(void)
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{
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return channels;
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}
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/**
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* Decode part of open MP3 file.
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*
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* \param buffer Decoded output.
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* \return Samples read for each channel.
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*/
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uint64_t decodeMp3(void* buffer)
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{
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size_t done = 0;
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mpg123_read(mh, buffer, *buffSize, &done);
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return done / (sizeof(int16_t));
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}
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/**
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* Free MP3 decoder.
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*/
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void exitMp3(void)
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{
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mpg123_close(mh);
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mpg123_delete(mh);
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mpg123_exit();
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}
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