Audio Over IP
Audio over IP refers to the transmission of digital audio across . This technology enables high-quality audio streams to be sent between devices and locations with minimal latency. AoIP can be used for broadcasting, live sound reinforcement, recording studios, and more.
Key concepts
Codec
To efficiently transmit audio over IP, the digital audio data is often compressed using a codec (compressor-decompressor). Codecs like AAC, MP3, and Opus are designed to reduce the amount of data needed to represent the audio without significantly compromising quality.
Packetization
Digital audio is divided into packets, small chunks of data that are transmitted over the network. Each packet contains a portion of the audio signal and metadata for routing and reassembling the audio on the receiving end.
Protocols
Several protocols are used to manage the transmission of audio over IP. These include for streaming audio, for signaling and controlling communications sessions, and more specialized protocols like Dante, AES67, and Ravenna, each designed for specific use cases and industries.
Synchronization
Synchronization is a critical aspect of Audio over IP systems, ensuring that audio packets from various sources arrive in time and are played back coherently. Synchronization may refer to clock synchronization between endpoints (i.e. the same function as word clock in digital audio), or between channels in a stream. Achieving precise synchronization across a network involves several key mechanisms:
Precision Time Protocol (PTP)
For environments requiring higher precision than NTP, PTP (defined in IEEE 1588) provides sub-microsecond accuracy, making it ideal for professional audio and video applications. Protocols like AES67 and Dante use PTP for clock synchronization between endpoints.
Sample Accurate Synchronization
In professional audio environments, it's essential that audio samples are aligned perfectly across multiple streams or channels. This can be achieved through sample-accurate timing information embedded in the audio packets or external clocking mechanisms provided by the AoIP protocol.
Jitter Buffers
To cope with timing variations (jitter) in packet arrival caused by network congestion or path variations, AoIP devices use jitter buffers. These temporarily store incoming packets to realign them into a steady stream before playback, ensuring smooth audio delivery.