avformat/rtp: support RGB/BGR for rfc4175

Reviewed-by: Lynne <dev@lynne.ee>
Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

libavformat/sdp.c

@@ -676,6 +676,12 @@ static char *sdp_write_media_attributes(char *buff, int size, AVStream *st, int
             case AV_PIX_FMT_YUV420P:
                 pix_fmt = "YCbCr-4:2:0";
                 break;
+            case AV_PIX_FMT_RGB24:
+                pix_fmt = "RGB";
+                break;
+            case AV_PIX_FMT_BGR24:
+                pix_fmt = "BGR";
+                break;
             default:
                 av_log(fmt, AV_LOG_ERROR, "Unsupported pixel format.\n");
                 return NULL;