Change default number of channels (used if unspecified in the format desc)

from 2 to 1, which is the actual value used in the spec. Fixes issue1978.

Path by John Wimer <john at god dot vtic dot net>.

Originally committed as revision 23414 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rtsp.h

@@ -52,7 +52,7 @@ enum RTSPTransport {
 #define RTSP_DEFAULT_PORT   554
 #define RTSP_MAX_TRANSPORTS 8
 #define RTSP_TCP_MAX_PACKET_SIZE 1472
-#define RTSP_DEFAULT_NB_AUDIO_CHANNELS 2
+#define RTSP_DEFAULT_NB_AUDIO_CHANNELS 1
 #define RTSP_DEFAULT_AUDIO_SAMPLERATE 44100
 #define RTSP_RTP_PORT_MIN 5000
 #define RTSP_RTP_PORT_MAX 10000