/*
* NAME: layer->I()
* DESCRIPTION: decode a single Layer I frame
*/
int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
{
struct mad_header *header = &frame->header;
unsigned int nch, bound, ch, s, sb, nb;
unsigned char allocation[2][32], scalefactor[2][32];
nch = MAD_NCHANNELS(header);
bound = 32;
if (header->mode == MAD_MODE_JOINT_STEREO) {
header->flags |= MAD_FLAG_I_STEREO;
bound = 4 + header->mode_extension * 4;
}
/* check CRC word */
if (header->flags & MAD_FLAG_PROTECTION) {
header->crc_check =
mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
header->crc_check);
if (header->crc_check != header->crc_target &&
!(frame->options & MAD_OPTION_IGNORECRC)) {
stream->error = MAD_ERROR_BADCRC;
return -1;
}
}
/* decode bit allocations */
for (sb = 0; sb < bound; ++sb) {
for (ch = 0; ch < nch; ++ch) {
nb = mad_bit_read(&stream->ptr, 4);
if (nb == 15) {
stream->error = MAD_ERROR_BADBITALLOC;
return -1;
}
allocation[ch][sb] = nb ? nb + 1 : 0;
}
}
for (sb = bound; sb < 32; ++sb) {
nb = mad_bit_read(&stream->ptr, 4);
if (nb == 15) {
stream->error = MAD_ERROR_BADBITALLOC;
return -1;
}
allocation[0][sb] =
allocation[1][sb] = nb ? nb + 1 : 0;
}
/* decode scalefactors */
for (sb = 0; sb < 32; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if (allocation[ch][sb]) {
scalefactor[ch][sb] = mad_bit_read(&stream->ptr, 6);
# 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] == 63) {
stream->error = MAD_ERROR_BADSCALEFACTOR;
return -1;
}
# endif
}
}
}
/* decode samples */
for (s = 0; s < 12; ++s) {
for (sb = 0; sb < bound; ++sb) {
for (ch = 0; ch < nch; ++ch) {
nb = allocation[ch][sb];
frame->sbsample[ch][s][sb] = nb ?
mad_f_mul(I_sample(&stream->ptr, nb),
sf_table[scalefactor[ch][sb]]) : 0;
}
}
for (sb = bound; sb < 32; ++sb) {
if ((nb = allocation[0][sb])) {
mad_fixed_t sample;
sample = I_sample(&stream->ptr, nb);
for (ch = 0; ch < nch; ++ch) {
frame->sbsample[ch][s][sb] =
mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
}
}
else {
for (ch = 0; ch < nch; ++ch)
frame->sbsample[ch][s][sb] = 0;
}
}
}
return 0;
}
int mad_layer_I(struct mad_stream *stream, struct mad_frame *frame)
{
struct mad_header *header = &frame->header;
unsigned int nch, bound, ch, s, sb, nb;
unsigned char allocation[2][32], scalefactor[2][32];
nch = MAD_NCHANNELS(header);
bound = 32;
if (header->mode == MAD_MODE_JOINT_STEREO) {
header->flags |= MAD_FLAG_I_STEREO;
bound = 4 + header->mode_extension * 4;
}
if (header->flags & MAD_FLAG_PROTECTION) {
header->crc_check =
mad_bit_crc(stream->ptr, 4 * (bound * nch + (32 - bound)),
header->crc_check);
if (header->crc_check != header->crc_target &&
!(frame->options & MAD_OPTION_IGNORECRC)) {
stream->error = MAD_ERROR_BADCRC;
return -1;
}
}
for (sb = 0; sb < bound; ++sb) {
for (ch = 0; ch < nch; ++ch) {
nb = mad_bit_read(&stream->ptr, 4);
if (nb == 15) {
stream->error = MAD_ERROR_BADBITALLOC;
return -1;
}
allocation[ch][sb] = nb ? nb + 1 : 0;
}
}
for (sb = bound; sb < 32; ++sb) {
nb = mad_bit_read(&stream->ptr, 4);
if (nb == 15) {
stream->error = MAD_ERROR_BADBITALLOC;
return -1;
}
allocation[0][sb] =
allocation[1][sb] = nb ? nb + 1 : 0;
}
for (sb = 0; sb < 32; ++sb) {
for (ch = 0; ch < nch; ++ch) {
if (allocation[ch][sb]) {
scalefactor[ch][sb] = (unsigned char)(mad_bit_read(&stream->ptr, 6));
if (scalefactor[ch][sb] == 63) {
stream->error = MAD_ERROR_BADSCALEFACTOR;
return -1;
}
}
}
}
for (s = 0; s < 12; ++s) {
for (sb = 0; sb < bound; ++sb) {
for (ch = 0; ch < nch; ++ch) {
nb = allocation[ch][sb];
frame->sbsample[ch][s][sb] = nb ?
mad_f_mul(I_sample(&stream->ptr, nb),
sf_table[scalefactor[ch][sb]]) : 0;
}
}
for (sb = bound; sb < 32; ++sb) {
if ((nb = allocation[0][sb])) {
mad_fixed_t sample;
sample = I_sample(&stream->ptr, nb);
for (ch = 0; ch < nch; ++ch) {
frame->sbsample[ch][s][sb] =
mad_f_mul(sample, sf_table[scalefactor[ch][sb]]);
}
}
else {
for (ch = 0; ch < nch; ++ch)
frame->sbsample[ch][s][sb] = 0;
}
}
}
return 0;
}