prores_kostya: fix incorrect picture_size field.

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

libavcodec/proresenc_kostya.c

@@ -818,7 +818,7 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
 
     orig_buf -= 8;
     frame_size = buf - orig_buf;
-    picture_size = buf - picture_size_pos - 6;
+    picture_size = buf - (picture_size_pos - 1);
     bytestream_put_be32(&orig_buf, frame_size);
     bytestream_put_be32(&picture_size_pos, picture_size);
 

tests/ref/fate/vsynth1-prores_kostya

@@ -1,4 +1,4 @@
-f8fe98b7f9bb66857c81dbca409a9037 *tests/data/fate/vsynth1-prores_kostya.mov
+e7a7e17a40df5d1296cea05d55bd5724 *tests/data/fate/vsynth1-prores_kostya.mov
 3858901 tests/data/fate/vsynth1-prores_kostya.mov
 0a4153637d0cc0a88a8bcbf04cfaf8c6 *tests/data/fate/vsynth1-prores_kostya.out.rawvideo
 stddev:    3.17 PSNR: 38.09 MAXDIFF:   39 bytes:  7603200/  7603200

tests/ref/fate/vsynth2-prores_kostya

@@ -1,4 +1,4 @@
-26adb18726c08dde23bc4bee2eb591e2 *tests/data/fate/vsynth2-prores_kostya.mov
+80dbde33cf16cde01e6229313ac7ddc7 *tests/data/fate/vsynth2-prores_kostya.mov
 3884586 tests/data/fate/vsynth2-prores_kostya.mov
 ca2f6c1162635dedfa468c90f1fdc0ef *tests/data/fate/vsynth2-prores_kostya.out.rawvideo
 stddev:    0.92 PSNR: 48.77 MAXDIFF:   10 bytes:  7603200/  7603200