From a3c900a0c48910b55b0e07f05eeaeda55ed2268f Mon Sep 17 00:00:00 2001
From: Peter Ross <pross@xvid.org>
Date: Sat, 21 Dec 2024 20:43:53 +1100
Subject: [PATCH] avcodec/lpc_functions: compute_lpc_coefs: add starting lpc
 order and err cache parameters

---
 libavcodec/aac/aacdec_dsp_template.c |  2 +-
 libavcodec/aacenc_tns.c              |  2 +-
 libavcodec/lpc.c                     |  2 +-
 libavcodec/lpc_functions.h           | 18 +++++++++++++-----
 libavcodec/ra288.c                   |  2 +-
 5 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/libavcodec/aac/aacdec_dsp_template.c b/libavcodec/aac/aacdec_dsp_template.c
index 8d31af22f8..b64944d548 100644
--- a/libavcodec/aac/aacdec_dsp_template.c
+++ b/libavcodec/aac/aacdec_dsp_template.c
@@ -185,7 +185,7 @@ static void AAC_RENAME(apply_tns)(void *_coef_param, TemporalNoiseShaping *tns,
                 continue;
 
             // tns_decode_coef
-            compute_lpc_coefs(tns->AAC_RENAME(coef)[w][filt], order, lpc, 0, 0, 0);
+            compute_lpc_coefs(tns->AAC_RENAME(coef)[w][filt], 0, order, lpc, 0, 0, 0, NULL);
 
             start = ics->swb_offset[FFMIN(bottom, mmm)];
             end   = ics->swb_offset[FFMIN(   top, mmm)];
diff --git a/libavcodec/aacenc_tns.c b/libavcodec/aacenc_tns.c
index 7884c035cb..2f27444025 100644
--- a/libavcodec/aacenc_tns.c
+++ b/libavcodec/aacenc_tns.c
@@ -117,7 +117,7 @@ void ff_aac_apply_tns(AACEncContext *s, SingleChannelElement *sce)
                 continue;
 
             // tns_decode_coef
-            compute_lpc_coefs(tns->coef[w][filt], order, lpc, 0, 0, 0);
+            compute_lpc_coefs(tns->coef[w][filt], 0, order, lpc, 0, 0, 0, NULL);
 
             start = ics->swb_offset[FFMIN(bottom, mmm)];
             end   = ics->swb_offset[FFMIN(   top, mmm)];
diff --git a/libavcodec/lpc.c b/libavcodec/lpc.c
index e793e54038..38c78d9521 100644
--- a/libavcodec/lpc.c
+++ b/libavcodec/lpc.c
@@ -267,7 +267,7 @@ int ff_lpc_calc_coefs(LPCContext *s,
 
         s->lpc_compute_autocorr(s->windowed_samples, blocksize, max_order, autoc);
 
-        compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
+        compute_lpc_coefs(autoc, 0, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1, NULL);
 
         for(i=0; i<max_order; i++)
             ref[i] = fabs(lpc[i][i]);
diff --git a/libavcodec/lpc_functions.h b/libavcodec/lpc_functions.h
index 57bcfab900..ea5f8868b9 100644
--- a/libavcodec/lpc_functions.h
+++ b/libavcodec/lpc_functions.h
@@ -51,22 +51,27 @@ typedef float LPC_TYPE_U;
  * Levinson-Durbin recursion.
  * Produce LPC coefficients from autocorrelation data.
  */
-static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
+static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int i, int max_order,
                                     LPC_TYPE *lpc, int lpc_stride, int fail,
-                                    int normalize)
+                                    int normalize, LPC_TYPE *err_ptr)
 {
     LPC_TYPE err = 0;
     LPC_TYPE *lpc_last = lpc;
 
     av_assert2(normalize || !fail);
 
-    if (normalize)
-        err = *autoc++;
+    if (normalize) {
+        if (i == 0)
+            err = *autoc++;
+        else {
+            err = *err_ptr;
+        }
+    }
 
     if (fail && (autoc[max_order - 1] == 0 || err <= 0))
         return -1;
 
-    for(int i = 0; i < max_order; i++) {
+    for( ; i < max_order; i++) {
         LPC_TYPE r = LPC_SRA_R(-autoc[i], 5);
 
         if (normalize) {
@@ -94,6 +99,9 @@ static inline int compute_lpc_coefs(const LPC_TYPE *autoc, int max_order,
         lpc += lpc_stride;
     }
 
+    if (err_ptr)
+        *err_ptr = err;
+
     return 0;
 }
 
diff --git a/libavcodec/ra288.c b/libavcodec/ra288.c
index a1ee3f7eba..550af7f29f 100644
--- a/libavcodec/ra288.c
+++ b/libavcodec/ra288.c
@@ -138,7 +138,7 @@ static void backward_filter(RA288Context *ractx,
 
     do_hybrid_window(ractx->vector_fmul, order, n, non_rec, temp, hist, rec, window);
 
-    if (!compute_lpc_coefs(temp, order, lpc, 0, 1, 1))
+    if (!compute_lpc_coefs(temp, 0, order, lpc, 0, 1, 1, NULL))
         ractx->vector_fmul(lpc, lpc, tab, FFALIGN(order, 16));
 
     memmove(hist, hist + n, move_size*sizeof(*hist));