Hi list! I noticed that when the phone of my wife calls the gsm codec will be used, but if someone calls the phone, alaw will be used: 00493511111111 calls 00493512222222: OpenWrt*CLI> sip show channels Peer User/ANR Call ID Format Hold Last Message Expiry Peer 192.168.200.11 00493512222222 5305ad0e07977dd 0x4 (ulaw) No Init: INVITE 0049351222 192.168.200.10 00493511111111 1481837b-c0a801 0x4 (ulaw) No Rx: INVITE 0049351111 00493512222222 calls 00493511111111: OpenWrt*CLI> sip show channels Peer User/ANR Call ID Format Hold Last Message Expiry Peer 192.168.200.10 00493511111111 5e21076a01b9483 0x8 (alaw) No Tx: ACK 0049351111 192.168.200.11 00493512222222 MCBsoNI2Cj266BB 0x2 (gsm) No Rx: ACK 0049351222 Could someone explain me why? Second question: I think, ulaw/alaw are better then gsm, isn't it? If so, how can I change it? Thanks Luca Bertoncello (lucabert at lucabert.de)
On Sunday 05 Jul 2015, Luca Bertoncello wrote:> Hi list! > > I noticed that when the phone of my wife calls the gsm codec will be used, > but if someone calls the phone, alaw will be used:> Could someone explain me why? > Second question: I think, ulaw/alaw are better then gsm, isn't it? > If so, how can I change it?GSM is the native codec used for calls to mobile phones; it uses lossy compression to achieve a low bit rate. A-law is the native codec used by physical exchanges on the land line network (PSTN and ISDN). It is non-lossy. It works by arranging the "steps" closer together near the zero line, and further apart away from it; so the difference between the actual signal and the nearest digital representation is small in proportion to the signal. To force the use of a-law, you need something like disallow=all allow=alaw at the top of the configuration file for the calling technology in question (sip.conf for SIP, chan_dahdi.conf for DAHDI, &c.). If you want to force a specific device to use a specific codec, then put an allow in the section for that device. -- AJS Note: Originating address only accepts e-mail from list! If replying off- list, change address to asterisk1list at earthshod dot co dot uk .
Zitat von A J Stiles <asterisk_list at earthshod.co.uk>: Hi,> GSM is the native codec used for calls to mobile phones; it uses lossy > compression to achieve a low bit rate. > > A-law is the native codec used by physical exchanges on the land line network > (PSTN and ISDN). It is non-lossy. It works by arranging the "steps" closer > together near the zero line, and further apart away from it; so the > difference > between the actual signal and the nearest digital representation is small in > proportion to the signal.Well, but for voice quality, which codec is better? alaw or gsm? Thanks Luca Bertoncello (lucabert at lucabert.de)