lavc/ffv1: drop redundant FFV1Context.quant_table

In all cases except decoding version 1 it's either not used, or contains
a copy of a table from quant_tables, which we can just as well use
directly.

When decoding version 1, we can just as well decode into
quant_tables[0], which would otherwise be unused.

libavcodec/ffv1.h

@@ -106,7 +106,6 @@ typedef struct FFV1Context {
     int ac;                              ///< 1=range coder <-> 0=golomb rice
     int ac_byte_count;                   ///< number of bytes used for AC coding
     PlaneContext plane[MAX_PLANES];
-    int16_t quant_table[MAX_CONTEXT_INPUTS][256];
     int16_t quant_tables[MAX_QUANT_TABLES][MAX_CONTEXT_INPUTS][256];
     int context_count[MAX_QUANT_TABLES];
     uint8_t state_transition[256];

libavcodec/ffv1dec.c

@@ -764,7 +764,7 @@ static int read_header(FFV1Context *f)
     ff_dlog(f->avctx, "%d %d %d\n",
             f->chroma_h_shift, f->chroma_v_shift, f->avctx->pix_fmt);
     if (f->version < 2) {
-        context_count = read_quant_tables(c, f->quant_table);
+        context_count = read_quant_tables(c, f->quant_tables[0]);
         if (context_count < 0) {
             av_log(f->avctx, AV_LOG_ERROR, "read_quant_table error\n");
             return AVERROR_INVALIDDATA;
@@ -834,7 +834,7 @@ static int read_header(FFV1Context *f)
                        sizeof(p->quant_table));
                 context_count = f->context_count[idx];
             } else {
-                memcpy(p->quant_table, f->quant_table, sizeof(p->quant_table));
+                memcpy(p->quant_table, f->quant_tables[0], sizeof(p->quant_table));
             }
 
             if (f->version <= 2) {
@@ -1067,7 +1067,11 @@ static int update_thread_context(AVCodecContext *dst, const AVCodecContext *src)
     fdst->use32bit     = fsrc->use32bit;
     memcpy(fdst->state_transition, fsrc->state_transition,
            sizeof(fdst->state_transition));
-    memcpy(fdst->quant_table, fsrc->quant_table, sizeof(fsrc->quant_table));
+
+    // in version 1 there is a single per-keyframe quant table, so
+    // we need to propagate it between threads
+    if (fsrc->version < 2)
+        memcpy(fdst->quant_tables[0], fsrc->quant_tables[0], sizeof(fsrc->quant_tables[0]));
 
     for (int i = 0; i < fdst->num_h_slices * fdst->num_v_slices; i++) {
         FFV1Context *fssrc = fsrc->slice_context[i];

libavcodec/ffv1enc.c

@@ -367,7 +367,7 @@ static void write_header(FFV1Context *f)
         put_symbol(c, state, f->chroma_v_shift, 0);
         put_rac(c, state, f->transparency);
 
-        write_quant_tables(c, f->quant_table);
+        write_quant_tables(c, f->quant_tables[f->context_model]);
     } else if (f->version < 3) {
         put_symbol(c, state, f->slice_count, 0);
         for (i = 0; i < f->slice_count; i++) {
@@ -735,15 +735,13 @@ static av_cold int encode_init(AVCodecContext *avctx)
     }
     s->context_count[0] = (11 * 11 * 11        + 1) / 2;
     s->context_count[1] = (11 * 11 * 5 * 5 * 5 + 1) / 2;
-    memcpy(s->quant_table, s->quant_tables[s->context_model],
-           sizeof(s->quant_table));
 
     for (i = 0; i < s->plane_count; i++) {
         PlaneContext *const p = &s->plane[i];
 
-        memcpy(p->quant_table, s->quant_table, sizeof(p->quant_table));
         p->quant_table_index = s->context_model;
         p->context_count     = s->context_count[p->quant_table_index];
+        memcpy(p->quant_table, s->quant_tables[p->quant_table_index], sizeof(p->quant_table));
     }
 
     if ((ret = ff_ffv1_allocate_initial_states(s)) < 0)