avcodec/pthread: fix ffv1 with 2 threads

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/pthread.c

@@ -651,9 +651,10 @@ int ff_thread_decode_frame(AVCodecContext *avctx,
      * If we're still receiving the initial packets, don't return a frame.
      */
 
-    if (fctx->delaying) {
-        if (fctx->next_decoding >= (avctx->thread_count-1-(avctx->codec_id == AV_CODEC_ID_FFV1))) fctx->delaying = 0;
+    if (fctx->next_decoding > (avctx->thread_count-1-(avctx->codec_id == AV_CODEC_ID_FFV1)))
+        fctx->delaying = 0;
 
+    if (fctx->delaying) {
         *got_picture_ptr=0;
         if (avpkt->size)
             return avpkt->size;