ffv1: allow selecting 1.3 by using -level

Note, 1.3 is not finalized and the bitstream will still change
do not use it yet. This option is just to make playing with it
easier, otherwise one would have to edit the source

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

libavcodec/ffv1.c

@@ -903,6 +903,11 @@ static av_cold int encode_init(AVCodecContext *avctx)
     if((avctx->flags & (CODEC_FLAG_PASS1|CODEC_FLAG_PASS2)) || avctx->slices>1)
         s->version = FFMAX(s->version, 2);
 
+    if(avctx->level == 3){
+        s->version = 3;
+        s->ec = 1;
+    }
+
     if(s->version >= 2 && avctx->strict_std_compliance > FF_COMPLIANCE_EXPERIMENTAL) {
         av_log(avctx, AV_LOG_ERROR, "Version 2 needed for requested features but version 2 is experimental and not enabled\n");
         return -1;