@@ -1096,7 +1096,6 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,

     FFV1Context *f      = avctx->priv_data;

     RangeCoder *const c = &f->slice_context[0]->c;

     AVFrame *const p    = f->picture.f;

-    int used_count      = 0;

     uint8_t keystate    = 128;

     uint8_t *buf_p;

     int i, ret;

@@ -1185,11 +1184,17 @@ FF_ENABLE_DEPRECATION_WARNINGS

         }

     }

-    for (i = 1; i < f->slice_count; i++) {

+    for (i = 0; i < f->slice_count; i++) {

         FFV1Context *fs = f->slice_context[i];

-        uint8_t *start  = pkt->data + (pkt->size - used_count) * (int64_t)i / f->slice_count;

+        uint8_t *start  = pkt->data + pkt->size * (int64_t)i / f->slice_count;

         int len         = pkt->size / f->slice_count;

-        ff_init_range_encoder(&fs->c, start, len);

+        if (i) {

+            ff_init_range_encoder(&fs->c, start, len);

+        } else {

+            av_assert0(fs->c.bytestream_end >= fs->c.bytestream_start + len);

+            av_assert0(fs->c.bytestream < fs->c.bytestream_start + len);

+            fs->c.bytestream_end = fs->c.bytestream_start + len;

+        }

     }

     avctx->execute(avctx, encode_slice, &f->slice_context[0], NULL,

                    f->slice_count, sizeof(void *));