avcodec/ffv1enc: update buffer check for 16bps

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 3728603f18)

Conflicts:

	libavcodec/ffv1enc.c
(cherry picked from commit c900c6e5c26cd86cf34f9c8d4347cedbd01f3935)

libavcodec/ffv1.c

@@ -437,7 +437,7 @@ static inline int encode_line(FFV1Context *s, int w, int_fast16_t *sample[2], in
     int run_mode=0;
 
     if(s->ac){
-        if(c->bytestream_end - c->bytestream < w*20){
+        if(c->bytestream_end - c->bytestream < w*35){
             av_log(s->avctx, AV_LOG_ERROR, "encoded frame too large\n");
             return -1;
         }