load_gsm.c

linux下的rtp的实例源代码

/* * 
 *  $Id: load_GSM.c 133 2005-05-09 17:35:14Z federico $
 *  
 *  This file is part of Fenice
 *
 *  Fenice -- Open Media Server
 *
 *  Copyright (C) 2004 by
 *  	
 *	- Giampaolo Mancini	<[e-mail]>
 *	- Francesco Varano	<[e-mail]>
 *	- Marco Penno		<[e-mail]>
 *	- Federico Ridolfo	<[e-mail]>
 *	- Eugenio Menegatti 	<[e-mail]>
 *	- Stefano Cau
 *	- Giuliano Emma
 *	- Stefano Oldrini
 * 
 *  Fenice is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  Fenice is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with Fenice; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *  
 * */

#include <unistd.h>

#include <fenice/utils.h>
#include <fenice/mediainfo.h>
#include <fenice/gsm.h>

int load_GSM(media_entry *p) {

	unsigned char byte1;
	int ret;
	
	if (!(p->description.flags & MED_PKT_LEN)) {
                                p->description.pkt_len=20; /* By default for GSM */
                                p->description.delta_mtime=p->description.pkt_len;
                                p->description.flags|=MED_PKT_LEN;
	}
	if ( (ret=mediaopen(p)) < 0)
		return ret;
        if (read(p->fd,&byte1,1) != 1) return ERR_PARSE;
        mediaclose(p);

        switch (byte1 & 0x07) {
                case 0: p->description.bitrate = 4750; break;
                case 1: p->description.bitrate = 5150; break;
                case 2: p->description.bitrate = 5900; break;
                case 3: p->description.bitrate = 6700; break;
                case 4: p->description.bitrate = 7400; break;
                case 5: p->description.bitrate = 7950; break;
                case 6: p->description.bitrate = 10200; break;
                case 7: p->description.bitrate = 12200; break;
        }       
        p->description.flags|=MED_BITRATE;      

        return ERR_NOERROR;
}