Quick facts about ABTO Software's VoIP SIP SDK for Windows:

License Details

No yearly/monthly fee

No limitation for number of users, channels, or products

Protocols Support

SIP

RTP

SDP

TCP/UDP

STUN

ICE

Development Features

ActiveX, COM, and plain dll files

NAT (Network Address Translation) support

Encryption on the basis of sRTP, DLS, and DTLS

DTMF (Dual Tone Multi Frequency) support

SIP Authentication

Codecs management

Basic samples (C#, C++, VB.NET, VB 6.0, and Delphi)

Custom samples (multiple SIP accounts, IVR, presence, and voice mail)

Log file on/off setting

End User Features

All versions of Windows OS, including Windows 8

Support of all kinds of Internet connections

SIP Registrar support (compatibility with most of SIP servers including Asterisk)

Works under firewall

Multiple sip accounts registration

Multiline support

Multi-party voice conference

Video call support

IM interface

Selecting of media input and output devices

Custom ringtone support

Configuration saving and loading

Conversation Specific Features

Calls operations:
- Hold/Retrieve Call
- Forward Call (Blind Call Transfer)
- Transfer Call (Attended Transfer)

Noise reduction (supression)
- AGC (Auto gain controller) support
- Adaptive silence detection
- Adaptive jitter buffer

Software volume control (including Mute Sound)

Playing file into conversation

Recording conversation into file

Redirection of calls to other phone lines

Available codecs:

H.263

H.264

G.711 (ALaw, muLaw)

G.726 (16k 24k 32k 40k)

G.729A

G.723

iLBC

LPC-10

Speex (Narrow, Wide)

L16

GSM