title: what should I set appsrc caps to fix "internal data stream error"?
body: <p>I'm trying to open an mp4 video decode it and send it to appsink. then recieve it from appsrc and save it on an mp4 file.</p>
  
  <p>I'm sure I've set the caps wrong.</p>
  
  <pre><code>const gchar *video_caps =
  "video/x-raw,width=1280,height=720,framerate=25/1";
  </code></pre>
  
  <p>first half of the pipeline:</p>
  
  <pre><code>  string = g_strdup_printf ("filesrc location=\"%s\" ! decodebin name=dec ! queue ! videoconvert ! appsink caps=\"%s\" name=testsink",
    in_filename, video_caps);
  </code></pre>
  
  <p>second half:</p>
  
  <pre><code>string = g_strdup_printf ("appsrc name=testsource caps=\"%s\" !x264enc ! mp4mux! filesink location=\"%s\"",
         video_caps,out_filename);
  </code></pre>
  
  <p>what should I set my caps to make it work? </p>
  
  <p>error I got:<code>Received error in sink(appsrc module)  Error: Internal data stream error.</code></p>