Don't convert bitdepth for !single-file or MD5.

... unless --output-bit-depth was set.

Change-Id: I3482eaf12e245eec24427518fccdd173f890f4b4

vpxdec.c

@@ -990,11 +990,11 @@ static int main_loop(int argc, const char **argv_) {
       }
 #if CONFIG_VP9_HIGHBITDEPTH
       // Default to codec bit depth if output bit depth not set
-      if (!output_bit_depth) {
+      if (!output_bit_depth && single_file && !do_md5) {
         output_bit_depth = img->bit_depth;
       }
       // Shift up or down if necessary
-      if (output_bit_depth != img->bit_depth) {
+      if (output_bit_depth != 0 && output_bit_depth != img->bit_depth) {
         const vpx_img_fmt_t shifted_fmt = output_bit_depth == 8 ?
             img->fmt ^ (img->fmt & VPX_IMG_FMT_HIGHBITDEPTH) :
             img->fmt | VPX_IMG_FMT_HIGHBITDEPTH;