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aacdec_usac: fix stereo alpha values for transients 

Typo.
Also added comments and fixed the branch underneath.
This commit is contained in:
Lynne 2024-06-07 04:13:54 +02:00
parent 7223523335
commit c2d459cb51
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GPG Key ID: A2FEA5F03F034464
3 changed files with 19 additions and 9 deletions
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1
libavcodec/aac/aacdec.c
View File

@ -1334,6 +1334,7 @@ static int decode_ics_info(AACDecContext *ac, IndividualChannelStream *ics,
ics->use_kb_window[1] = ics->use_kb_window[0];
ics->use_kb_window[0] = get_bits1(gb);
}
ics->prev_num_window_groups = FFMAX(ics->num_window_groups, 1);
ics->num_window_groups = 1;
ics->group_len[0] = 1;
if (ics->window_sequence[0] == EIGHT_SHORT_SEQUENCE) {

1
libavcodec/aac/aacdec.h
View File

@ -164,6 +164,7 @@ typedef struct IndividualChannelStream {
enum WindowSequence window_sequence[2];
uint8_t use_kb_window[2]; ///< If set, use Kaiser-Bessel window, otherwise use a sine window.
int num_window_groups;
int prev_num_window_groups; ///< Previous frame's number of window groups
uint8_t group_len[8];
LongTermPrediction ltp;
const uint16_t *swb_offset; ///< table of offsets to the lowest spectral coefficient of a scalefactor band, sfb, for a particular window

26
libavcodec/aac/aacdec_usac.c
View File

@ -658,7 +658,9 @@ static int decode_spectrum_and_dequant_ac(AACDecContext *s, float coef[1024],
static int decode_usac_stereo_cplx(AACDecContext *ac, AACUsacStereo *us,
ChannelElement *cpe, GetBitContext *gb,
int num_window_groups, int indep_flag)
int num_window_groups,
int prev_num_window_groups,
int indep_flag)
{
int delta_code_time;
IndividualChannelStream *ics = &cpe->ch[0].ics;
@ -696,15 +698,18 @@ static int decode_usac_stereo_cplx(AACDecContext *ac, AACUsacStereo *us,
float last_alpha_q_im = 0;
if (delta_code_time) {
if (g) {
last_alpha_q_re = us->prev_alpha_q_re[(g - 1)*cpe->max_sfb_ste + sfb];
last_alpha_q_im = us->prev_alpha_q_im[(g - 1)*cpe->max_sfb_ste + sfb];
} else if ((ics->window_sequence[0] == EIGHT_SHORT_SEQUENCE) &&
ics->window_sequence[1] == EIGHT_SHORT_SEQUENCE ||
ics->window_sequence[1] == EIGHT_SHORT_SEQUENCE) {
/* Transient, after the first group - use the current frame,
* previous window, alpha values. */
last_alpha_q_re = us->alpha_q_re[(g - 1)*cpe->max_sfb_ste + sfb];
last_alpha_q_im = us->alpha_q_im[(g - 1)*cpe->max_sfb_ste + sfb];
} else if (!g &&
(ics->window_sequence[0] == EIGHT_SHORT_SEQUENCE) &&
(ics->window_sequence[1] == EIGHT_SHORT_SEQUENCE)) {
/* The spec doesn't explicitly mention this, but it doesn't make
* any other sense otherwise! */
last_alpha_q_re = us->prev_alpha_q_re[7*cpe->max_sfb_ste + sfb];
last_alpha_q_im = us->prev_alpha_q_im[7*cpe->max_sfb_ste + sfb];
const int wg = prev_num_window_groups - 1;
last_alpha_q_re = us->prev_alpha_q_re[wg*cpe->max_sfb_ste + sfb];
last_alpha_q_im = us->prev_alpha_q_im[wg*cpe->max_sfb_ste + sfb];
} else {
last_alpha_q_re = us->prev_alpha_q_re[g*cpe->max_sfb_ste + sfb];
last_alpha_q_im = us->prev_alpha_q_im[g*cpe->max_sfb_ste + sfb];
@ -749,6 +754,7 @@ static int setup_sce(AACDecContext *ac, SingleChannelElement *sce,
IndividualChannelStream *ics = &sce->ics;
/* Setup window parameters */
ics->prev_num_window_groups = FFMAX(ics->num_window_groups, 1);
if (ics->window_sequence[0] == EIGHT_SHORT_SEQUENCE) {
if (usac->core_frame_len == 768) {
ics->swb_offset = ff_swb_offset_96[usac->rate_idx];
@ -869,7 +875,9 @@ static int decode_usac_stereo_info(AACDecContext *ac, AACUSACConfig *usac,
memset(cpe->ms_mask, 0xFF, sizeof(cpe->ms_mask));
} else if ((us->ms_mask_mode == 3) && !ec->stereo_config_index) {
ret = decode_usac_stereo_cplx(ac, us, cpe, gb,
ics1->num_window_groups, indep_flag);
ics1->num_window_groups,
ics1->prev_num_window_groups,
indep_flag);
if (ret < 0)
return ret;
}