mirror of
https://github.com/RaySollium99/picodrive.git
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137 lines
3.2 KiB
C
137 lines
3.2 KiB
C
// Some mp3 related code for Sega/Mega CD
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// (c) Copyright 2007, Grazvydas "notaz" Ignotas
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#include <stdio.h>
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#include <string.h>
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#include "../../Pico/sound/mix.h"
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#include "code940/940shared.h"
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#include "helix/pub/mp3dec.h"
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static short mp3_out_buffer[2*1152];
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static HMP3Decoder mp3dec = 0;
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static int mp3_buffer_offs = 0;
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extern _940_ctl_t *shared_ctl;
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extern unsigned char *mp3_mem;
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extern int PsndRate;
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static int try_get_header(unsigned char *buff, MP3FrameInfo *fi)
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{
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int ret, offs1, offs = 0;
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while (1)
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{
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offs1 = MP3FindSyncWord(buff + offs, 2048 - offs);
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if (offs1 < 0) return -2;
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offs += offs1;
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if (2048 - offs < 4) return -3;
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// printf("trying header %08x\n", *(int *)(buff + offs));
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ret = MP3GetNextFrameInfo(mp3dec, fi, buff + offs);
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if (ret == 0 && fi->bitrate != 0) break;
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offs++;
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}
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return ret;
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}
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int mp3_get_bitrate(FILE *f, int len)
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{
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unsigned char buff[2048];
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MP3FrameInfo fi;
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int ret;
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memset(buff, 0, 2048);
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if (!mp3dec) mp3dec = MP3InitDecoder();
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fseek(f, 0, SEEK_SET);
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ret = fread(buff, 1, 2048, f);
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fseek(f, 0, SEEK_SET);
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if (ret <= 0) return -1;
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ret = try_get_header(buff, &fi);
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if (ret != 0 || fi.bitrate == 0) {
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// try to read somewhere around the middle
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fseek(f, len>>1, SEEK_SET);
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fread(buff, 1, 2048, f);
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fseek(f, 0, SEEK_SET);
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ret = try_get_header(buff, &fi);
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}
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if (ret != 0) return ret;
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// printf("bitrate: %i\n", fi.bitrate / 1000);
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return fi.bitrate / 1000;
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}
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static void mp3_decode(void)
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{
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// tried copying this to cached mem, no improvement noticed
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int mp3_offs = shared_ctl->mp3_offs;
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unsigned char *readPtr = mp3_mem + mp3_offs;
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int bytesLeft = shared_ctl->mp3_len - mp3_offs;
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int offset; // frame offset from readPtr
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int err;
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if (bytesLeft <= 0) return; // EOF, nothing to do
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offset = MP3FindSyncWord(readPtr, bytesLeft);
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if (offset < 0) {
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shared_ctl->mp3_offs = shared_ctl->mp3_len;
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return; // EOF
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}
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readPtr += offset;
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bytesLeft -= offset;
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err = MP3Decode(mp3dec, &readPtr, &bytesLeft, mp3_out_buffer, 0);
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if (err) {
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if (err == ERR_MP3_INDATA_UNDERFLOW) {
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shared_ctl->mp3_offs = shared_ctl->mp3_len; // EOF
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return;
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} else if (err <= -6 && err >= -12) {
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// ERR_MP3_INVALID_FRAMEHEADER, ERR_MP3_INVALID_*
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// just try to skip the offending frame..
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readPtr++;
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}
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shared_ctl->mp3_errors++;
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shared_ctl->mp3_lasterr = err;
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}
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shared_ctl->mp3_offs = readPtr - mp3_mem;
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}
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void mp3_update_local(int *buffer, int length, int stereo)
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{
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int length_mp3, shr = 0;
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void (*mix_samples)(int *dest_buf, short *mp3_buf, int count) = mix_16h_to_32;
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length_mp3 = length;
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if (PsndRate == 22050) { mix_samples = mix_16h_to_32_s1; length_mp3 <<= 1; shr = 1; }
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else if (PsndRate == 11025) { mix_samples = mix_16h_to_32_s2; length_mp3 <<= 2; shr = 2; }
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if (1152 - mp3_buffer_offs >= length_mp3) {
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mix_samples(buffer, mp3_out_buffer + mp3_buffer_offs*2, length<<1);
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mp3_buffer_offs += length_mp3;
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} else {
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int left = 1152 - mp3_buffer_offs;
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mix_samples(buffer, mp3_out_buffer + mp3_buffer_offs*2, (left>>shr)<<1);
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mp3_decode();
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mp3_buffer_offs = length_mp3 - left;
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mix_samples(buffer + ((left>>shr)<<1), mp3_out_buffer, (mp3_buffer_offs>>shr)<<1);
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}
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}
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void mp3_start_local(void)
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{
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mp3_buffer_offs = 0;
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mp3_decode();
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}
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