shithub: dav1d

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Add "disable_cdf_update" support

--- a/src/decode.c

+++ b/src/decode.c

@@ -2134,7 +2134,7 @@

     ts->last_qidx = f->frame_hdr.quant.yac;

     memset(ts->last_delta_lf, 0, sizeof(ts->last_delta_lf));

-    msac_init(&ts->msac, data, sz);

+    msac_init(&ts->msac, data, sz, f->frame_hdr.disable_cdf_update);

     ts->tiling.row = tile_row;

     ts->tiling.col = tile_col;

--- a/src/msac.c

+++ b/src/msac.c

@@ -157,7 +157,8 @@

                                   uint16_t *const cdf, const unsigned n_symbols)

 {

     const unsigned val = msac_decode_symbol(c, cdf, n_symbols);

-    update_cdf(cdf, val, n_symbols);

+    if(c->allow_update_cdf)

+        update_cdf(cdf, val, n_symbols);

     return val;

 }

@@ -164,21 +165,23 @@

 unsigned msac_decode_bool_adapt(MsacContext *const c, uint16_t *const cdf) {

     const unsigned bit = msac_decode_bool(c, *cdf >> EC_PROB_SHIFT);

-    // update_cdf() specialized for boolean CDFs

-    const unsigned count = cdf[1];

-    const int rate = (count >> 4) | 4;

-    if (bit) {

-        cdf[0] += (32768 - cdf[0]) >> rate;

-    } else {

-        cdf[0] -= cdf[0] >> rate;

+    if(c->allow_update_cdf){

+        // update_cdf() specialized for boolean CDFs

+        const unsigned count = cdf[1];

+        const int rate = (count >> 4) | 4;

+        if (bit) {

+            cdf[0] += (32768 - cdf[0]) >> rate;

+        } else {

+            cdf[0] -= cdf[0] >> rate;

+        }

+        cdf[1] = count + (count < 32);

     }

-    cdf[1] = count + (count < 32);

     return bit;

 }

 void msac_init(MsacContext *const s, const uint8_t *const data,

-               const size_t sz)

+               const size_t sz, const int disable_cdf_update_flag)

 {

     s->buf_pos = data;

     s->buf_end = data + sz;

@@ -185,5 +188,6 @@

     s->dif = ((ec_win)1 << (EC_WIN_SIZE - 1)) - 1;

     s->rng = 0x8000;

     s->cnt = -15;

+    s->allow_update_cdf = !disable_cdf_update_flag;

     ctx_refill(s);

 }

--- a/src/msac.h

+++ b/src/msac.h

@@ -40,12 +40,13 @@

     ec_win dif;

     uint16_t rng;

     int cnt;

+    int allow_update_cdf;

 } MsacContext;

 #define EC_PROB_SHIFT 6

 #define EC_BOOL_EPROB 256

-void msac_init(MsacContext *c, const uint8_t *data, size_t sz);

+void msac_init(MsacContext *c, const uint8_t *data, size_t sz, int disable_cdf_update_flag);

 unsigned msac_decode_symbol(MsacContext *s, const uint16_t *cdf,

                             const unsigned n_symbols);

 unsigned msac_decode_symbol_adapt(MsacContext *s, uint16_t *cdf,