ref: dc725301592117ad0e70a0ab21926dcf5302ed31
dir: /sys/src/cmd/audio/mp3dec/frame.c/
/* * libmad - MPEG audio decoder library * Copyright (C) 2000-2004 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: frame.c,v 1.29 2004/02/04 22:59:19 rob Exp $ */ # ifdef HAVE_CONFIG_H # include "config.h" # endif # include "global.h" # include "bit.h" # include "stream.h" # include "frame.h" # include "layer12.h" # include "layer3.h" static unsigned long const bitrate_table[5][15] = { /* MPEG-1 */ { 0, 32000, 64000, 96000, 128000, 160000, 192000, 224000, /* Layer I */ 256000, 288000, 320000, 352000, 384000, 416000, 448000 }, { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, /* Layer II */ 128000, 160000, 192000, 224000, 256000, 320000, 384000 }, { 0, 32000, 40000, 48000, 56000, 64000, 80000, 96000, /* Layer III */ 112000, 128000, 160000, 192000, 224000, 256000, 320000 }, /* MPEG-2 LSF */ { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, /* Layer I */ 128000, 144000, 160000, 176000, 192000, 224000, 256000 }, { 0, 8000, 16000, 24000, 32000, 40000, 48000, 56000, /* Layers */ 64000, 80000, 96000, 112000, 128000, 144000, 160000 } /* II & III */ }; static unsigned int const samplerate_table[3] = { 44100, 48000, 32000 }; static int (*const decoder_table[3])(struct mad_stream *, struct mad_frame *) = { mad_layer_I, mad_layer_II, mad_layer_III }; /* * NAME: header->init() * DESCRIPTION: initialize header struct */ void mad_header_init(struct mad_header *header) { header->layer = 0; header->mode = 0; header->mode_extension = 0; header->emphasis = 0; header->bitrate = 0; header->samplerate = 0; header->crc_check = 0; header->crc_target = 0; header->flags = 0; header->private_bits = 0; } /* * NAME: frame->init() * DESCRIPTION: initialize frame struct */ void mad_frame_init(struct mad_frame *frame) { mad_header_init(&frame->header); frame->options = 0; frame->overlap = 0; mad_frame_mute(frame); } /* * NAME: frame->finish() * DESCRIPTION: deallocate any dynamic memory associated with frame */ void mad_frame_finish(struct mad_frame *frame) { mad_header_finish(&frame->header); if (frame->overlap) { free(frame->overlap); frame->overlap = 0; } } /* * NAME: decode_header() * DESCRIPTION: read header data and following CRC word */ static int decode_header(struct mad_header *header, struct mad_stream *stream) { unsigned int index; header->flags = 0; header->private_bits = 0; /* header() */ /* syncword */ mad_bit_skip(&stream->ptr, 11); /* MPEG 2.5 indicator (really part of syncword) */ if (mad_bit_read(&stream->ptr, 1) == 0) header->flags |= MAD_FLAG_MPEG_2_5_EXT; /* ID */ if (mad_bit_read(&stream->ptr, 1) == 0) header->flags |= MAD_FLAG_LSF_EXT; else if (header->flags & MAD_FLAG_MPEG_2_5_EXT) { stream->error = MAD_ERROR_LOSTSYNC; return -1; } /* layer */ header->layer = 4 - mad_bit_read(&stream->ptr, 2); if (header->layer == 4) { stream->error = MAD_ERROR_BADLAYER; return -1; } /* protection_bit */ if (mad_bit_read(&stream->ptr, 1) == 0) { header->flags |= MAD_FLAG_PROTECTION; header->crc_check = mad_bit_crc(stream->ptr, 16, 0xffff); } /* bitrate_index */ index = mad_bit_read(&stream->ptr, 4); if (index == 15) { stream->error = MAD_ERROR_BADBITRATE; return -1; } if (header->flags & MAD_FLAG_LSF_EXT) header->bitrate = bitrate_table[3 + (header->layer >> 1)][index]; else header->bitrate = bitrate_table[header->layer - 1][index]; /* sampling_frequency */ index = mad_bit_read(&stream->ptr, 2); if (index == 3) { stream->error = MAD_ERROR_BADSAMPLERATE; return -1; } header->samplerate = samplerate_table[index]; if (header->flags & MAD_FLAG_LSF_EXT) { header->samplerate /= 2; if (header->flags & MAD_FLAG_MPEG_2_5_EXT) header->samplerate /= 2; } /* padding_bit */ if (mad_bit_read(&stream->ptr, 1)) header->flags |= MAD_FLAG_PADDING; /* private_bit */ if (mad_bit_read(&stream->ptr, 1)) header->private_bits |= MAD_PRIVATE_HEADER; /* mode */ header->mode = 3 - mad_bit_read(&stream->ptr, 2); /* mode_extension */ header->mode_extension = mad_bit_read(&stream->ptr, 2); /* copyright */ if (mad_bit_read(&stream->ptr, 1)) header->flags |= MAD_FLAG_COPYRIGHT; /* original/copy */ if (mad_bit_read(&stream->ptr, 1)) header->flags |= MAD_FLAG_ORIGINAL; /* emphasis */ header->emphasis = mad_bit_read(&stream->ptr, 2); # if defined(OPT_STRICT) /* * ISO/IEC 11172-3 says this is a reserved emphasis value, but * streams exist which use it anyway. Since the value is not important * to the decoder proper, we allow it unless OPT_STRICT is defined. */ if (header->emphasis == MAD_EMPHASIS_RESERVED) { stream->error = MAD_ERROR_BADEMPHASIS; return -1; } # endif /* error_check() */ /* crc_check */ if (header->flags & MAD_FLAG_PROTECTION) header->crc_target = mad_bit_read(&stream->ptr, 16); return 0; } /* * NAME: free_bitrate() * DESCRIPTION: attempt to discover the bitstream's free bitrate */ static int free_bitrate(struct mad_stream *stream, struct mad_header const *header) { struct mad_bitptr keep_ptr; unsigned long rate = 0; unsigned int pad_slot, slots_per_frame; unsigned char const *ptr = 0; keep_ptr = stream->ptr; pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0; slots_per_frame = (header->layer == MAD_LAYER_III && (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144; while (mad_stream_sync(stream) == 0) { struct mad_stream peek_stream; struct mad_header peek_header; peek_stream = *stream; peek_header = *header; if (decode_header(&peek_header, &peek_stream) == 0 && peek_header.layer == header->layer && peek_header.samplerate == header->samplerate) { unsigned int N; ptr = mad_bit_nextbyte(&stream->ptr); N = ptr - stream->this_frame; if (header->layer == MAD_LAYER_I) { rate = (unsigned long) header->samplerate * (N - 4 * pad_slot + 4) / 48 / 1000; } else { rate = (unsigned long) header->samplerate * (N - pad_slot + 1) / slots_per_frame / 1000; } if (rate >= 8) break; } mad_bit_skip(&stream->ptr, 8); } stream->ptr = keep_ptr; if (rate < 8 || (header->layer == MAD_LAYER_III && rate > 640)) { stream->error = MAD_ERROR_LOSTSYNC; return -1; } stream->freerate = rate * 1000; return 0; } /* * NAME: header->decode() * DESCRIPTION: read the next frame header from the stream */ int mad_header_decode(struct mad_header *header, struct mad_stream *stream) { register unsigned char const *ptr, *end; unsigned int pad_slot, N; ptr = stream->next_frame; end = stream->bufend; if (ptr == 0) { stream->error = MAD_ERROR_BUFPTR; goto fail; } /* stream skip */ if (stream->skiplen) { if (!stream->sync) ptr = stream->this_frame; if (end - ptr < stream->skiplen) { stream->skiplen -= end - ptr; stream->next_frame = end; stream->error = MAD_ERROR_BUFLEN; goto fail; } ptr += stream->skiplen; stream->skiplen = 0; stream->sync = 1; } sync: /* synchronize */ if (stream->sync) { if (end - ptr < MAD_BUFFER_GUARD) { stream->next_frame = ptr; stream->error = MAD_ERROR_BUFLEN; goto fail; } else if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) { /* mark point where frame sync word was expected */ stream->this_frame = ptr; stream->next_frame = ptr + 1; stream->error = MAD_ERROR_LOSTSYNC; goto fail; } } else { mad_bit_init(&stream->ptr, ptr); if (mad_stream_sync(stream) == -1) { if (end - stream->next_frame >= MAD_BUFFER_GUARD) stream->next_frame = end - MAD_BUFFER_GUARD; stream->error = MAD_ERROR_BUFLEN; goto fail; } ptr = mad_bit_nextbyte(&stream->ptr); } /* begin processing */ stream->this_frame = ptr; stream->next_frame = ptr + 1; /* possibly bogus sync word */ mad_bit_init(&stream->ptr, stream->this_frame); if (decode_header(header, stream) == -1) goto fail; /* calculate free bit rate */ if (header->bitrate == 0) { if ((stream->freerate == 0 || !stream->sync || (header->layer == MAD_LAYER_III && stream->freerate > 640000)) && free_bitrate(stream, header) == -1) goto fail; header->bitrate = stream->freerate; header->flags |= MAD_FLAG_FREEFORMAT; } /* calculate beginning of next frame */ pad_slot = (header->flags & MAD_FLAG_PADDING) ? 1 : 0; if (header->layer == MAD_LAYER_I) N = ((12 * header->bitrate / header->samplerate) + pad_slot) * 4; else { unsigned int slots_per_frame; slots_per_frame = (header->layer == MAD_LAYER_III && (header->flags & MAD_FLAG_LSF_EXT)) ? 72 : 144; N = (slots_per_frame * header->bitrate / header->samplerate) + pad_slot; } /* verify there is enough data left in buffer to decode this frame */ if (N + MAD_BUFFER_GUARD > end - stream->this_frame) { stream->next_frame = stream->this_frame; stream->error = MAD_ERROR_BUFLEN; goto fail; } stream->next_frame = stream->this_frame + N; if (!stream->sync) { /* check that a valid frame header follows this frame */ ptr = stream->next_frame; if (!(ptr[0] == 0xff && (ptr[1] & 0xe0) == 0xe0)) { ptr = stream->next_frame = stream->this_frame + 1; goto sync; } stream->sync = 1; } header->flags |= MAD_FLAG_INCOMPLETE; return 0; fail: stream->sync = 0; return -1; } /* * NAME: frame->decode() * DESCRIPTION: decode a single frame from a bitstream */ int mad_frame_decode(struct mad_frame *frame, struct mad_stream *stream) { frame->options = stream->options; /* header() */ /* error_check() */ if (!(frame->header.flags & MAD_FLAG_INCOMPLETE) && mad_header_decode(&frame->header, stream) == -1) goto fail; /* audio_data() */ frame->header.flags &= ~MAD_FLAG_INCOMPLETE; if (decoder_table[frame->header.layer - 1](stream, frame) == -1) { if (!MAD_RECOVERABLE(stream->error)) stream->next_frame = stream->this_frame; goto fail; } /* ancillary_data() */ if (frame->header.layer != MAD_LAYER_III) { struct mad_bitptr next_frame; mad_bit_init(&next_frame, stream->next_frame); stream->anc_ptr = stream->ptr; stream->anc_bitlen = mad_bit_length(&stream->ptr, &next_frame); mad_bit_finish(&next_frame); } return 0; fail: stream->anc_bitlen = 0; return -1; } /* * NAME: frame->mute() * DESCRIPTION: zero all subband values so the frame becomes silent */ void mad_frame_mute(struct mad_frame *frame) { unsigned int s, sb; for (s = 0; s < 36; ++s) { for (sb = 0; sb < 32; ++sb) { frame->sbsample[0][s][sb] = frame->sbsample[1][s][sb] = 0; } } if (frame->overlap) { for (s = 0; s < 18; ++s) { for (sb = 0; sb < 32; ++sb) { (*frame->overlap)[0][sb][s] = (*frame->overlap)[1][sb][s] = 0; } } } }