output-example: Set sample_fmt to SAMPLE_FMT_S16.

Originally committed as revision 23597 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/output-example.c

@@ -68,6 +68,7 @@ static AVStream *add_audio_stream(AVFormatContext *oc, enum CodecID codec_id)
     c->codec_type = AVMEDIA_TYPE_AUDIO;
 
     /* put sample parameters */
+    c->sample_fmt = SAMPLE_FMT_S16;
     c->bit_rate = 64000;
     c->sample_rate = 44100;
     c->channels = 2;