Hi, I have developed a UMTS core network using a home nodeB (HNB) which the
mobile phones (or UEs) can register on my network and get the required
services such as call service. I have implemented all the required
procedures for call service and I can establish a successful call for my
connected UEs.
In one of the most important procedures, i.e **Call Proceeding**, I have
identified the coding of speech transferred between UEs and core. Here is
my coding options (in wireshark):
GSM A-I/F DTAP - Call Proceeding
Protocol Discriminator: Call Control; call related SS messages (3)
.... 0011 = Protocol discriminator: Call Control; call related
SS messages (0x3)
1... .... = TI flag: allocated by receiver
.000 .... = TIO: 0
00.. .... = Sequence number: 0
..00 0010 = DTAP Call Control Message Type: Call Proceeding (0x02)
Bearer Capability 1 - (Spare)
Element ID: 0x04
Length: 6
Octet 3
0... .... = Extension: Extended
.11. .... = Radio channel requirement: Spare
...0 .... = Coding standard: GSM standardized coding
.... 0... = Transfer mode: circuit
.... .000 = Information transfer capability: Speech (0x0)
Octets 3a - Speech Versions
0... .... = Extension: Extended
.0.. .... = Coding: octet used for extension of information
transfer capability
..00 .... = Spare bit(s): 0
.... 0010 = Speech version indication: GSM full rate speech
version 2(GSM EFR) (0x2)
0... .... = Extension: Extended
.0.. .... = Coding: octet used for extension of information
transfer capability
..00 .... = Spare bit(s): 0
.... 1000 = Speech version indication: GSM full rate speech
version 5(FR AMR-WB) (0x8)
0... .... = Extension: Extended
.0.. .... = Coding: octet used for extension of information
transfer capability
..00 .... = Spare bit(s): 0
.... 0100 = Speech version indication: GSM full rate speech
version 3(FR AMR) (0x4)
0... .... = Extension: Extended
.0.. .... = Coding: octet used for extension of information
transfer capability
..00 .... = Spare bit(s): 0
.... 0101 = Speech version indication: GSM half rate speech
version 3(HR AMR) (0x5)
1... .... = Extension: No Extension
.0.. .... = Coding: octet used for extension of information
transfer capability
..00 .... = Spare bit(s): 0
.... 0001 = Speech version indication: GSM half rate speech
version 1(GSM HR) (0x1)
So I can see the RTP packets transferred between UE and core. An instance
is mentioned here (in wireshark):
Real-Time Transport Protocol
[Stream setup by RANAP (frame 2950)]
10.. .... = Version: RFC 1889 Version (2)
..0. .... = Padding: False
...0 .... = Extension: False
.... 0000 = Contributing source identifiers count: 0
0... .... = Marker: False
Payload type: DynamicRTP-Type-96 (96)
Sequence number: 56611
[Extended sequence number: 56611]
Timestamp: 424448575
Synchronization Source identifier: 0x5c260101 (1545994497)
RFC 2198: Redundant Audio Data
Header 1: PT=ITU-T G.728
0... .... = Follow: Not set
.000 1111 = Payload type: ITU-T G.728 (15)
Payload: 0028ba44776b3eee7a050039cdaa521cc20ac08d2bcf1818…
I have aggregated all RTP packets payload. How can I convert the aggregated
bytes to a hearable audio?
--
*When there is much light, The shadow is deep...*