From 6d1009cb9d888996c544a3ee95245b0df44bb2e0 Mon Sep 17 00:00:00 2001
From: Steven Liu <lq@chinaffmpeg.org>
Date: Wed, 21 Aug 2019 19:34:49 +0800
Subject: [PATCH] doc/examples/decode_video: add input file format information
 for usage

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
---
 doc/examples/decode_video.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/doc/examples/decode_video.c b/doc/examples/decode_video.c
index 5a9d43f689..169188a4b9 100644
--- a/doc/examples/decode_video.c
+++ b/doc/examples/decode_video.c
@@ -95,7 +95,8 @@ int main(int argc, char **argv)
     AVPacket *pkt;
 
     if (argc <= 2) {
-        fprintf(stderr, "Usage: %s <input file> <output file>\n", argv[0]);
+        fprintf(stderr, "Usage: %s <input file> <output file>\n"
+                "And check your input file is encoded by mpeg1video please.\n", argv[0]);
         exit(0);
     }
     filename    = argv[1];