Siren (codec)

Siren refers to a family of audio codecs designed for low-bandwidth, high-quality voice and audio communication. These codecs are primarily used in Voice over IP (VoIP) applications and video conferencing. The Siren codecs are known for their robustness to packet loss and their ability to deliver clear audio even under challenging network conditions.

There are primarily two codecs identified under the Siren name:

• Siren 7: Also known as G.722.1 Annex C or ITU-T G.722.1C, Siren 7 is a narrowband audio codec operating at 7 kHz sampling rate. It provides high-quality audio at low bitrates, typically ranging from 24 to 32 kbps. Siren 7 is often used in conjunction with G.722, providing a wider bandwidth audio option when available.

• Siren 14: Also known as G.722.1 Annex D or ITU-T G.722.1D, Siren 14 is a wideband audio codec operating at 14 kHz sampling rate. It delivers even higher audio quality than Siren 7 at bitrates ranging from 48 to 64 kbps. Siren 14 offers a more natural and immersive audio experience compared to narrowband codecs, making it suitable for applications where clarity and detail are essential.

Both Siren 7 and Siren 14 employ transform coding techniques, specifically Modified Discrete Cosine Transform (MDCT), to efficiently compress audio signals. They also include error resilience mechanisms to mitigate the impact of packet loss, which is common in IP networks. These error resilience features are crucial for maintaining audio quality in real-time communication environments. The algorithms are mathematically complex and are often implemented in specialized digital signal processors (DSPs) or optimized software libraries.

The main advantages of the Siren codecs are their low bandwidth requirements combined with relatively high audio quality. This makes them suitable for use in a variety of applications, including:

• VoIP phones and softphones
• Video conferencing systems
• Audio conferencing bridges
• Collaboration platforms

Due to its patented nature, the use of Siren codecs may require licensing from the patent holders.