lavc/ffv1dec: move slice_reset_contexts to per-slice context

libavcodec/ffv1.h

@@ -86,8 +86,19 @@ typedef struct FFV1SliceContext {
     RangeCoder c;
 
     int ac_byte_count;                   ///< number of bytes used for AC coding
+
+    union {
+        // decoder-only
+        struct {
+            int slice_reset_contexts;
+        };
+
+        // encoder-only
+        struct {
             uint64_t rc_stat[256][2];
             uint64_t (*rc_stat2[MAX_QUANT_TABLES])[32][2];
+        };
+    };
 } FFV1SliceContext;
 
 typedef struct FFV1Context {
@@ -135,7 +146,6 @@ typedef struct FFV1Context {
     int max_slice_count;
     int num_v_slices;
     int num_h_slices;
-    int slice_reset_contexts;
 
     FFV1SliceContext *slices;
 } FFV1Context;

libavcodec/ffv1dec.c

@@ -239,7 +239,7 @@ static int decode_slice_header(const FFV1Context *f, FFV1Context *fs,
     }
 
     if (fs->version > 3) {
-        fs->slice_reset_contexts = get_rac(c, state);
+        sc->slice_reset_contexts = get_rac(c, state);
         sc->slice_coding_mode = get_symbol(c, state, 0);
         if (sc->slice_coding_mode != 1) {
             sc->slice_rct_by_coef = get_symbol(c, state, 0);
@@ -309,7 +309,7 @@ static int decode_slice(AVCodecContext *c, void *arg)
     }
     if ((ret = ff_ffv1_init_slice_state(f, sc)) < 0)
         return ret;
-    if ((p->flags & AV_FRAME_FLAG_KEY) || fs->slice_reset_contexts) {
+    if ((p->flags & AV_FRAME_FLAG_KEY) || sc->slice_reset_contexts) {
         ff_ffv1_clear_slice_state(f, sc);
     } else if (fs->slice_damaged) {
         return AVERROR_INVALIDDATA;