avcodec/utils: improve guess_correct_pts() by considerng mixed dts/pts use caused by NOPTSs

No testcase known, this is a theoretical improvment
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/utils.c

@@ -1966,11 +1966,15 @@ static int64_t guess_correct_pts(AVCodecContext *ctx,
     if (dts != AV_NOPTS_VALUE) {
         ctx->pts_correction_num_faulty_dts += dts <= ctx->pts_correction_last_dts;
         ctx->pts_correction_last_dts = dts;
-    }
+    } else if (reordered_pts != AV_NOPTS_VALUE)
+        ctx->pts_correction_last_dts = reordered_pts;
+
     if (reordered_pts != AV_NOPTS_VALUE) {
         ctx->pts_correction_num_faulty_pts += reordered_pts <= ctx->pts_correction_last_pts;
         ctx->pts_correction_last_pts = reordered_pts;
-    }
+    } else if(dts != AV_NOPTS_VALUE)
+        ctx->pts_correction_last_pts = dts;
+
     if ((ctx->pts_correction_num_faulty_pts<=ctx->pts_correction_num_faulty_dts || dts == AV_NOPTS_VALUE)
        && reordered_pts != AV_NOPTS_VALUE)
         pts = reordered_pts;