diago

The media package provides an optimized framework for handling RTP/RTCP media streams. It is designed around the Go standard library's io.Reader and io.Writer interfaces, allowing developers to chain readers and writers to build interceptors, encoders, and decoders without significant memory allocation overhead or contention.

Key features include:

• SDP building for alaw, ulaw, and dtmf formats.
• RTP/RTCP receiving and logging.
• Extendable MediaSession handling for hardware like microphones and speakers.
• DTMF encoding/decoding via RFC4733.
• RTP/RTCP session and monitoring capabilities.

The diago audio package provides support for several audio processing tasks, including:

• PCM encoding and decoding
• WAV file reading and writing

The package uses a layered approach to media processing by chaining standard library interfaces.

For receiving media (Reader flow): AudioDecoder $\leftrightarrow$ RTPPacketReader $\leftrightarrow$ RTPSession $\leftrightarrow$ MediaSession

For sending media (Writer flow): AudioEncoder $\leftrightarrow$ RTPPacketWriter $\leftrightarrow$ RTPSession $\leftrightarrow$ MediaSession

By following this pattern, you can insert custom logic (like interceptors or transformations) anywhere in the chain by implementing the appropriate io.Reader or io.Writer.

To work with media in this package, you need to understand the following abstractions and how they compose:

• Media Session: Represents the mapping between an SDP (Session Description Protocol) media description and a session created based on local and remote addresses.
• RTP Session: Manages the RTP/RTCP session. It uses a MediaSession underneath to provide the networking layer.
• RTP Packet Reader: Depacketizes RTP packets and exposes the payload as an io.Reader. This is typically chained to an RTP Session.
• RTP Packet Writer: Packetizes a payload into RTP packets as an io.Writer. This is typically chained to an RTP Session.

When debugging VOIP issues, you can enable tracing for SIP, RTCP, and RTP packets. Note that enabling media.RTPDebug will dump every single RTP packet, which can be very verbose.

sip.SIPDebug = true // Enables SIP tracing
media.RTCPDebug = true // Enables RTCP tracing
media.RTPDebug = true // Enables RTP tracing. NOTE: It will dump every RTP Packet

The diago audio package requires the opus C library for various encoding and decoding tasks. Depending on your Linux distribution, use the following commands to install the necessary dependencies:

Ubuntu

Install libopus0 using apt.

Fedora

Install opus-devel and opusfile-devel using dnf.

# Ubuntu
sudo apt install libopus0

# Fedora
sudo dnf install opus-devel
sudo dnf install opusfile-devel

To run the playback example, which acts as a media server, use the go run command pointing to the playback example directory. Once running, the server will be ready to receive media connections.

go run ./examples/playback

To run the DTMF playback example as a server, use the go run command pointing to the example directory. This starts a local server capable of receiving calls and processing DTMF tones.

go run ./examples/dtmf

The DialogServerSession struct is the primary interface for handling inbound SIP calls (UAS - User Agent Server). It embeds sipgo.DialogServerSession and extends it with media handling capabilities via DialogMedia.

Key responsibilities include:

• Responding to SIP signaling (Ringing, Trying, Progress).
• Managing media sessions (SDP negotiation, early media, answering calls).
• Handling call control (Hold, Unhold, Re-Invite, Refer, Hangup).
• Managing media updates and re-invites.

var session *diago.DialogServerSession
// session is typically provided by the diago server upon receiving an INVITE

When your application receives a REFER request, you can use dialogHandleRefer or dialogHandleReferTransaction to process it.

dialogHandleRefer is used when you want to provide a callback (OnReferDialogFunc) that receives the new dialog created by the REFER operation. This is useful for managing the lifecycle of the referred call.

dialogHandleReferTransaction provides a more granular approach using ReferTransaction, allowing you to manually Accept the transaction and control the invitation process via Accept(ctx, opts).