app_conference with asterisk-1.4.26 not working

Hi,

I want to have video conference using sip phone where i have already install app_conference but still it’s not working on CLI we can see following messages

__sip_reliable_xmit – Executing [100@conf:1] Answer(“SIP/9891318796-091f51b8”, “”) in new stack

__sip_reliable_xmit – Executing [100@conf:2] Conference(“SIP/9891318796-091f51b8”, “1234|MTV”) in new stack

__sip_reliable_xmit – Incoming call: Got SIP response 488 “Not Acceptable Here” back from 192.168.1.21
[Nov 25 13:11:16] NOTICE[19089]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘192.168.1.21’
[Nov 25 13:11:16] NOTICE[19089]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘192.168.1.21’
[Nov 25 13:11:16] NOTICE[19089]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘192.168.1.21’
[Nov 25 13:11:17] NOTICE[19069]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘0.0.0.0’
[Nov 25 13:11:18] NOTICE[19069]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘0.0.0.0’

__sip_reliable_xmit – Incoming call: Got SIP response 488 “Not Acceptable Here” back from 192.168.1.21
– B-channel 0/13 successfully restarted on span 1
– B-channel 0/14 successfully restarted on span 1

__sip_reliable_xmit
__sip_reliable_xmit[Nov 25 13:11:26] NOTICE[19045]: chan_sip.c:16180 handle_request_subscribe: Received SIP subscribe for peer without mailbox: 9891318796
– B-channel 0/15 successfully restarted on span 1
[Nov 25 13:11:31] ERROR[19045]: rtp.c:2554 ast_rtcp_write_rr: RTCP RR transmission error, rtcp halted
– B-channel 0/17 successfully restarted on span 1
[Nov 25 13:11:36] NOTICE[19089]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘0.0.0.0’
[Nov 25 13:11:36] NOTICE[19089]: rtp.c:1334 ast_rtp_read: Unknown RTP codec 126 received from ‘0.0.0.0’

Thanks in Advance if some one can help me on the same please revert asap.