img2enc: support 16bit per sample yuv in split planes.

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

libavformat/img2enc.c

@@ -100,6 +100,10 @@ static int write_packet(AVFormatContext *s, AVPacket *pkt)
     if(img->split_planes){
         int ysize = codec->width * codec->height;
         int usize = ((-codec->width)>>desc->log2_chroma_w) * ((-codec->height)>>desc->log2_chroma_h);
+        if (desc->comp[0].depth_minus1 >= 8) {
+            ysize *= 2;
+            usize *= 2;
+        }
         avio_write(pb[0], pkt->data        , ysize);
         avio_write(pb[1], pkt->data + ysize        , usize);
         avio_write(pb[2], pkt->data + ysize + usize, usize);