/* * * This file is part of libmpeg3 * * LibMPEG3 * Author: Adam Williams * Page: heroine.linuxbox.com * Page: http://www.smalltalkconsulting.com/html/mpeg3source.html (for Squeak) * LibMPEG3 was originally licenced under GPL. It was relicensed by the author under the LGPL and the Squeak license on Nov 1st, 2000 This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Also licensed under the Squeak license. http://www.squeak.org/license.html */ /* Changed Sept 15th by John M McIntosh to support Macintosh & Squeak */ #include "mpeg3audio.h" #include "tables.h" #include /* Return 1 if the head check doesn't find a header. */ int mpeg3audio_head_check(unsigned long head) { if((head & 0xffe00000) != 0xffe00000) return 1; if(!((head >> 17) & 3)) return 1; if(((head >> 12) & 0xf) == 0xf) return 1; if(!((head >> 12) & 0xf)) return 1; if(((head >> 10) & 0x3) == 0x3 ) return 1; if(((head >> 19) & 1) == 1 && ((head >> 17) & 3) == 3 && ((head >> 16) & 1) == 1) return 1; if((head & 0xffff0000) == 0xfffe0000) return 1; return 0; } int mpeg3audio_decode_header(mpeg3audio_t *audio) { if(audio->newhead & (1 << 20)) { audio->lsf = (audio->newhead & (1 << 19)) ? 0x0 : 0x1; audio->mpeg35 = 0; } else { audio->lsf = 1; audio->mpeg35 = 1; } audio->layer = 4 - ((audio->newhead >> 17) & 3); if(audio->mpeg35) audio->sampling_frequency_code = 6 + ((audio->newhead >> 10) & 0x3); else audio->sampling_frequency_code = ((audio->newhead >> 10) & 0x3) + (audio->lsf * 3); audio->error_protection = ((audio->newhead >> 16) & 0x1) ^ 0x1; audio->bitrate_index = ((audio->newhead >> 12) & 0xf); audio->padding = ((audio->newhead >> 9) & 0x1); audio->extension = ((audio->newhead >> 8) & 0x1); audio->mode = ((audio->newhead >> 6) & 0x3); audio->mode_ext = ((audio->newhead >> 4) & 0x3); audio->copyright = ((audio->newhead >> 3) & 0x1); audio->original = ((audio->newhead >> 2) & 0x1); audio->emphasis = audio->newhead & 0x3; audio->channels = (audio->mode == MPG_MD_MONO) ? 1 : 2; if(audio->channels > 1) audio->single = -1; else audio->single = 3; audio->prev_framesize = audio->framesize; if(!audio->bitrate_index) return 1; audio->bitrate = 1000 * mpeg3_tabsel_123[audio->lsf][audio->layer - 1][audio->bitrate_index]; switch(audio->layer) { case 1: audio->framesize = (long)mpeg3_tabsel_123[audio->lsf][0][audio->bitrate_index] * 12000; audio->framesize /= mpeg3_freqs[audio->sampling_frequency_code]; audio->framesize = ((audio->framesize + audio->padding) << 2) - 4; break; case 2: audio->framesize = (long)mpeg3_tabsel_123[audio->lsf][1][audio->bitrate_index] * 144000; audio->framesize /= mpeg3_freqs[audio->sampling_frequency_code]; audio->framesize += audio->padding - 4; break; case 3: if(audio->lsf) audio->ssize = (audio->channels == 1) ? 9 : 17; else audio->ssize = (audio->channels == 1) ? 17 : 32; if(audio->error_protection) audio->ssize += 2; audio->framesize = (long)mpeg3_tabsel_123[audio->lsf][2][audio->bitrate_index] * 144000; audio->framesize /= mpeg3_freqs[audio->sampling_frequency_code] << (audio->lsf); audio->framesize = audio->framesize + audio->padding - 4; break; default: return 1; } if(audio->framesize > MAXFRAMESIZE) return 1; return 0; } int mpeg3audio_read_frame_body(mpeg3audio_t *audio) { int i; for(i = 0; i < audio->framesize; i++) { audio->bsbuf[i] = mpeg3bits_getbits(audio->astream, 8); } return 0; } /* Seek to the start of the previous header */ int mpeg3audio_prev_header(mpeg3audio_t *audio) { int result = 0, i, len = audio->avg_framesize; for(i = 0; i < len && !result; i++) { mpeg3bits_getbits_reverse(audio->astream, 8); } /* Get reading in the forward direction again. */ result |= mpeg3bits_refill(audio->astream); return result; } /* Read the next header */ int mpeg3audio_read_header(mpeg3audio_t *audio) { unsigned int code; int i; int try2 = 0; int result = 0; switch(audio->format) { case AUDIO_AC3: //JMM result = mpeg3audio_read_ac3_header(audio); break; case AUDIO_MPEG: /* Layer 1 not supported */ if(audio->layer == 1) { fprintf(stderr, "mpeg3audio_new: layer 1 not supported\n"); result = 1; } audio->newhead = mpeg3bits_showbits(audio->astream, 32); if(!mpeg3bits_eof(audio->astream) && (mpeg3audio_head_check(audio->newhead) || mpeg3audio_decode_header(audio))) { do { try2++; mpeg3bits_getbyte_noptr(audio->astream); audio->newhead = mpeg3bits_showbits(audio->astream, 32); }while(!mpeg3bits_eof(audio->astream) && try2 < 65536 && (mpeg3audio_head_check(audio->newhead) || mpeg3audio_decode_header(audio))); } /* Skip the 4 bytes containing the header */ mpeg3bits_getbits(audio->astream, 32); break; case AUDIO_PCM: mpeg3audio_read_pcm_header(audio); break; } return mpeg3bits_eof(audio->astream); }