Quick Guide: Which Audio Codec Should I Use? Choosing the Right Audio Coding Algorithm for Remote Broadcasts and for Permanent IP-Audio Connections

APPLICATION NOTE

As the saying goes, engineers love standards — that’s why there are so many of them! In the world of audio codecs, there are plenty, each with unique advantages that make them suitable for different remote transmission situations.

In fact, most hardware codecs (such as the Telos Z/IP ONE, ProSTREAM, and Zephyr iPort PLUS, as well as those from other broadcast equipment manufacturers) offer a huge choice of audio coding algorithms. Choice is good! But with unhelpful names like “G.722”, “AAC-LD”, and “Layer 2”, it can be tough figuring out which coding algorithm is best for a given purpose or Internet connection.

With this in mind, we present the following data as a quick reference to the strengths of the most common codecs, and the situations in which you may find them most useful.

Codec Characteristics:

CODEC Bitrates Audio Expectations Typical Use Case AAC-ELD 48 - 64 kbps Excellent quality for low Live broadcasts of voice or music. Can use for music if neces- bitrates, full audio range, sary. Quick interaction with studio hosts and callers. mono or stereo, low delay. Error concealment. AAC-HE 16 - 96 kbps Excellent quality for low Music at lower bitrates. Best for one-way broadcasts where bitrates for voice and tight interaction with studio hosts or callers is not critical. music. Full audio range. Works at very low bitrates with some compromise in quality. Relatively high delay. Error concealment. AAC-LD 112 - 320 kbps Excellent, full-range Music/voice at medium bitrates. When medium bandwidth audio quality for medium is available and interaction with studio hosts or callers is bitrates. Low delay. Error needed, this is a great choice. concealment. AAC 80 - 320 kbps Excellent, full-range Music at medium bitrates. For the medium range of bitrates, audio quality for medium this is the best codec to choose when a little delay is OK. bitrates. Slightly higher Quality is fully “awesome”, especially at 256 kbps and higher. delay. Error concealment. Layer 2 112 - 384 kbps Excellent quality at Music/voice at medium bitrates to other brands of codecs. medium-high bitrates. Layer 2 is a great choice, especially for compatibility across Very compatible with other different brands of codecs. brands of equipment. G.722 64 kbps Good voice quality (7 kHz) Voice at low bitrate to other brands of codecs. Not “high when low delay and com- quality”, but much better than a standard telephone call. It’s patibility is needed. Also the most compatible low bitrate codec with any other brand. called “HD Voice” G.711 56 - 64 kbps Low quality, low delay This is a “phone call”. Often used for compatibility for SIP mono voice. Only 3.3 kHz (VoIP) calls to/from regular telephones. audio. aptX® Enhanced 384 - 576 kbps Excellent quality, full audio aptX® Enhanced is primarily used in professional broadcast bandwidth, low delay. Op- applications where low delay is desired and cascading coding tional on some codecs. algorithms may be encountered. PCM Linear 1,536 - 2,304 kbps Perfect quality, full band- Perfect audio for perfect connections. If you’ve got the bandwidth, low delay. No error width and a perfect IP path (low jitter and no packet loss), concealment. this is the perfect “algorithm”. Bit rate is not variable, but is fixed for given mono/stereo and bit-depth parameters.

+1 (216) 241-7225 | TELOSALLIANCE.COM APPLICATION NOTE: WHICH AUDIO CODEC SHOULD I USE?

Codec Features at a Glance:

CODEC Mono/ Lower Lower Remote STL & Error Highly Stereo Bitrates Delay Broadcasts Infrastructure Concealment Compatible AAC-ELD M/S ü ü ü ü AAC-HE M/S ü ü ü AAC-LD M/S ü ü ü AAC M/S ü ü Layer 2 M/S ü ü G.722 M ü ü ü ü G.711 M ü ü ü aptX® Enhanced M/S ü ü PCM Linear M/S ü ü

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