/*
* NAME: layer->II()
* DESCRIPTION: decode a single Layer II frame
*/
int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
{
struct mad_header *header = &frame->header;
struct mad_bitptr start;
unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
unsigned char const *offsets;
unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
mad_fixed_t samples[3];
nch = MAD_NCHANNELS(header);
if (header->flags & MAD_FLAG_LSF_EXT)
index = 4;
else {
switch (nch == 2 ? header->bitrate / 2 : header->bitrate) {
case 32000:
case 48000:
index = (header->samplerate == 32000) ? 3 : 2;
break;
case 56000:
case 64000:
case 80000:
index = 0;
break;
default:
index = (header->samplerate == 48000) ? 0 : 1;
}
}
sblimit = sbquant_table[index].sblimit;
offsets = sbquant_table[index].offsets;
bound = 32;
if (header->mode == MAD_MODE_JOINT_STEREO) {
header->flags |= MAD_FLAG_I_STEREO;
bound = 4 + header->mode_extension * 4;
}
if (bound > sblimit)
bound = sblimit;
start = stream->ptr;
/* decode bit allocations */
for (sb = 0; sb < bound; ++sb) {
nbal = bitalloc_table[offsets[sb]].nbal;
for (ch = 0; ch < nch; ++ch)
allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
}
for (sb = bound; sb < sblimit; ++sb) {
nbal = bitalloc_table[offsets[sb]].nbal;
allocation[0][sb] =
allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
}
/* decode scalefactor selection info */
for (sb = 0; sb < sblimit; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if (allocation[ch][sb])
scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
}
}
/* check CRC word */
if (header->flags & MAD_FLAG_PROTECTION) {
header->crc_check =
mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
header->crc_check);
if (header->crc_check != header->crc_target &&
!(frame->options & MAD_OPTION_IGNORECRC)) {
stream->error = MAD_ERROR_BADCRC;
return -1;
}
}
/* decode scalefactors */
for (sb = 0; sb < sblimit; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if (allocation[ch][sb]) {
scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
switch (scfsi[ch][sb]) {
case 2:
scalefactor[ch][sb][2] =
scalefactor[ch][sb][1] =
scalefactor[ch][sb][0];
break;
case 0:
scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
/* fall through */
case 1:
case 3:
scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
}
if (scfsi[ch][sb] & 1)
scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
# if defined(OPT_STRICT)
/*
* Scalefactor index 63 does not appear in Table B.1 of
* ISO/IEC 11172-3. Nonetheless, other implementations accept it,
* so we only reject it if OPT_STRICT is defined.
*/
if (scalefactor[ch][sb][0] == 63 ||
scalefactor[ch][sb][1] == 63 ||
scalefactor[ch][sb][2] == 63) {
stream->error = MAD_ERROR_BADSCALEFACTOR;
return -1;
}
# endif
}
}
}
/* decode samples */
for (gr = 0; gr < 12; ++gr) {
for (sb = 0; sb < bound; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if ((index = allocation[ch][sb])) {
index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
II_samples(&stream->ptr, &qc_table[index], samples);
for (s = 0; s < 3; ++s) {
frame->sbsample[ch][3 * gr + s][sb] =
mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
}
}
else {
for (s = 0; s < 3; ++s)
frame->sbsample[ch][3 * gr + s][sb] = 0;
}
}
}
for (sb = bound; sb < sblimit; ++sb) {
if ((index = allocation[0][sb])) {
index = offset_table[bitalloc_table[offsets[sb]].offset][index - 1];
II_samples(&stream->ptr, &qc_table[index], samples);
for (ch = 0; ch < nch; ++ch) {
for (s = 0; s < 3; ++s) {
frame->sbsample[ch][3 * gr + s][sb] =
mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
}
}
}
else {
for (ch = 0; ch < nch; ++ch) {
for (s = 0; s < 3; ++s)
frame->sbsample[ch][3 * gr + s][sb] = 0;
}
}
}
for (ch = 0; ch < nch; ++ch) {
for (s = 0; s < 3; ++s) {
for (sb = sblimit; sb < 32; ++sb)
frame->sbsample[ch][3 * gr + s][sb] = 0;
}
}
}
return 0;
}
/*
* NAME: layer->II()
* DESCRIPTION: decode a single Layer II frame
*/
int mad_layer_II(struct mad_stream *stream, struct mad_frame *frame)
{
struct mad_header *header = &frame->header;
struct mad_bitptr start;
unsigned int index, sblimit, nbal, nch, bound, gr, ch, s, sb;
unsigned char const *offsets;
unsigned char allocation[2][32], scfsi[2][32], scalefactor[2][32][3];
mad_fixed_t samples[3];
nch = MAD_NCHANNELS(header);
if (header->flags & MAD_FLAG_LSF_EXT)
index = 4;
else if (header->flags & MAD_FLAG_FREEFORMAT)
goto freeformat;
else {
unsigned long bitrate_per_channel;
bitrate_per_channel = header->bitrate;
if (nch == 2) {
bitrate_per_channel /= 2;
# if defined(OPT_STRICT)
/*
* ISO/IEC 11172-3 allows only single channel mode for 32, 48, 56, and
* 80 kbps bitrates in Layer II, but some encoders ignore this
* restriction. We enforce it if OPT_STRICT is defined.
*/
if (bitrate_per_channel <= 28000 || bitrate_per_channel == 40000) {
stream->error = MAD_ERROR_BADMODE;
return -1;
}
# endif
}
else { /* nch == 1 */
if (bitrate_per_channel > 192000) {
/*
* ISO/IEC 11172-3 does not allow single channel mode for 224, 256,
* 320, or 384 kbps bitrates in Layer II.
*/
stream->error = MAD_ERROR_BADMODE;
return -1;
}
}
if (bitrate_per_channel <= 48000)
index = (header->samplerate == 32000) ? 3 : 2;
else if (bitrate_per_channel <= 80000)
index = 0;
else {
freeformat:
index = (header->samplerate == 48000) ? 0 : 1;
}
}
sblimit = sbquant_table[index].sblimit;
offsets = sbquant_table[index].offsets;
bound = 32;
if (header->mode == MAD_MODE_JOINT_STEREO) {
header->flags |= MAD_FLAG_I_STEREO;
bound = 4 + header->mode_extension * 4;
}
if (bound > sblimit)
bound = sblimit;
start = stream->ptr;
/* decode bit allocations */
for (sb = 0; sb < bound; ++sb) {
nbal = bitalloc_table[offsets[sb]].nbal;
for (ch = 0; ch < nch; ++ch)
allocation[ch][sb] = mad_bit_read(&stream->ptr, nbal);
}
for (sb = bound; sb < sblimit; ++sb) {
nbal = bitalloc_table[offsets[sb]].nbal;
allocation[0][sb] =
allocation[1][sb] = mad_bit_read(&stream->ptr, nbal);
}
/* decode scalefactor selection info */
for (sb = 0; sb < sblimit; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if (allocation[ch][sb])
scfsi[ch][sb] = mad_bit_read(&stream->ptr, 2);
}
}
/* check CRC word */
if (header->flags & MAD_FLAG_PROTECTION) {
header->crc_check =
mad_bit_crc(start, mad_bit_length(&start, &stream->ptr),
header->crc_check);
if (header->crc_check != header->crc_target &&
!(frame->options & MAD_OPTION_IGNORECRC)) {
stream->error = MAD_ERROR_BADCRC;
return -1;
}
}
/* decode scalefactors */
for (sb = 0; sb < sblimit; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if (allocation[ch][sb]) {
scalefactor[ch][sb][0] = mad_bit_read(&stream->ptr, 6);
switch (scfsi[ch][sb]) {
case 2:
scalefactor[ch][sb][2] =
scalefactor[ch][sb][1] =
scalefactor[ch][sb][0];
break;
case 0:
scalefactor[ch][sb][1] = mad_bit_read(&stream->ptr, 6);
/* fall through */
case 1:
case 3:
scalefactor[ch][sb][2] = mad_bit_read(&stream->ptr, 6);
}
if (scfsi[ch][sb] & 1)
scalefactor[ch][sb][1] = scalefactor[ch][sb][scfsi[ch][sb] - 1];
# if defined(OPT_STRICT)
/*
* Scalefactor index 63 does not appear in Table B.1 of
* ISO/IEC 11172-3. Nonetheless, other implementations accept it,
* so we only reject it if OPT_STRICT is defined.
*/
if (scalefactor[ch][sb][0] == 63 ||
scalefactor[ch][sb][1] == 63 ||
scalefactor[ch][sb][2] == 63) {
stream->error = MAD_ERROR_BADSCALEFACTOR;
return -1;
}
# endif
}
}
}
/* decode samples */
for (gr = 0; gr < 12; ++gr) {
for (sb = 0; sb < bound; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if ((index = allocation[ch][sb])) {
int off = bitalloc_table[offsets[sb]].offset;
index = offset_table[off][index - 1];
II_samples(&stream->ptr, &qc_table[index], samples);
for (s = 0; s < 3; ++s) {
(*frame->sbsample)[ch][3 * gr + s][sb] =
mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
}
}
else {
for (s = 0; s < 3; ++s)
(*frame->sbsample)[ch][3 * gr + s][sb] = 0;
}
}
}
for (sb = bound; sb < sblimit; ++sb) {
if ((index = allocation[0][sb])) {
int off = bitalloc_table[offsets[sb]].offset;
index = offset_table[off][index - 1];
II_samples(&stream->ptr, &qc_table[index], samples);
for (ch = 0; ch < nch; ++ch) {
for (s = 0; s < 3; ++s) {
(*frame->sbsample)[ch][3 * gr + s][sb] =
mad_f_mul(samples[s], sf_table[scalefactor[ch][sb][gr / 4]]);
}
}
}
else {
for (ch = 0; ch < nch; ++ch) {
for (s = 0; s < 3; ++s)
(*frame->sbsample)[ch][3 * gr + s][sb] = 0;
}
}
}
for (ch = 0; ch < nch; ++ch) {
for (s = 0; s < 3; ++s) {
for (sb = sblimit; sb < 32; ++sb)
(*frame->sbsample)[ch][3 * gr + s][sb] = 0;
}
}
}
return 0;
}