ref: 61f4c085c402af665b436f6d010d61107551d8a3
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;
}
}
}
}