update readme

@@ -110,6 +110,7 @@ cd simple-rtmp-server/trunk
 * [Usage: How to forward stream to other server?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleForward)
 * [Usage: How to deploy low lantency application?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleRealtime)
 * [Usage: How to deploy SRS on ARM?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleARM)
+* [Usage: How to ingest file/stream/device to SRS?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleIngest)
 * [Usage: How to use SRS-HTTP-server to delivery HTTP/HLS stream?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleHTTP)
 * [Usage: How to show the demo of SRS?](https://github.com/winlinvip/simple-rtmp-server/wiki/SampleDemo)
 * [Usage: Solution using SRS?](https://github.com/winlinvip/simple-rtmp-server/wiki/Sample)

@@ -116,6 +116,7 @@ vhost ingest.srs.com {
         # @remark, the output is specified following.
         engine {
             # @see enabled of transcode engine.
+            # if disabled or vcodec/acodec not specified, use copy.
             # default: off.
             enable          off;
             # output stream. variables:

+# use ffmpeg to ingest file/stream/device to SRS
+# @see https://github.com/winlinvip/simple-rtmp-server/wiki/SampleIngest
+# @see full.conf for detail config.
+
+listen              1935;
+vhost __defaultVhost__ {
+    ingest {
+        enable      on;
+        input {
+            type    file;
+            url     ./doc/source.200kbps.768x320.flv;
+        }
+        ffmpeg      ./objs/ffmpeg/bin/ffmpeg;
+        engine {
+            enable          off;
+            output          rtmp://127.0.0.1:[port]/live?vhost=[vhost]/livestream;
+        }
+    }
+}

@@ -303,7 +303,9 @@ int SrsIngester::initialize_ffmpeg(SrsFFMPEG* ffmpeg, SrsConfDirective* vhost, S
         srs_error("invalid ingest type=%s, ret=%d", input_type.c_str(), ret);
     }
     
-    if (!engine || !_srs_config->get_engine_enabled(engine)) {
+    std::string vcodec = _srs_config->get_engine_vcodec(engine);
+    std::string acodec = _srs_config->get_engine_acodec(engine);
+    if (!engine || !_srs_config->get_engine_enabled(engine) || vcodec.empty() || acodec.empty()) {
         if ((ret = ffmpeg->initialize_copy()) != ERROR_SUCCESS) {
             return ret;
         }