Audio Compass

Your Low-Cost Audio Over IP Broadcast Software Solution

Audio Compass NavigatorTM

Audio Compass P2PTM

Codec Notes & Recommendations

* Apt-x Enhanced
* Celt
* G.722
* RAW-PCM
* Speex
* Other



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	Apt-x Enhanced

	Description: Apt-X Enhanced audio coding is now regarded as the de-facto standard for high quality audio delivery throughout the Pro-audio and Broadcast market. Enhanced apt-X has been embraced by the broadcast industry over recent years and is the algorithm of choice for AoIP Networks. Features Include: Compression Ratio 4:1, Outstanding audio quality, Low audio coding delay, No duelling effects with other algorithms, Based on Time Domain ADPCM Principles and not psychoacoustic masking, No issue with concatenation - suitable for up to 15 consecutive passes, Interoperability with over 20,000 installed Radio Audio Broadcast Systems Applications, and Broadcast Studio Transmitter Links or Studio to Studio Links. Notes: This is a good choice for the best sounding audio but requires more bandwidth than most. Perfect for voice and music and is the fullest algorithm to use for superior quality audio when multiple rounds of encoding take place along the audio chain.
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	Celt

	Description: The CELT ultra-low delay audio codec is a compression algorithm for audio. Like MP3, Vorbis and AAC, it is suitable for transmitting music with high quality. CELT stands for "Constrained Energy Lapped Transform". CELT is suitable for both speech and music and currently features ultra-low latency (typically from 3 to 9 ms) and support for both speech and music. Notes: CELT is a cousin to the Speex codec but is primarily designed for speech and music. With slightly more bandwidth required, it is an excellent low-bandwidth solution for voice and music. If you need to send music, consider CELT for low-bandwidth and apt-x for better quality and when more bandwidth is required. CELT and apt-x are our two best music codecs that are designed specifically for the Internet.
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	G.722

	Description: G.722 is a ITU-T standard 7 kHz wideband speech codec operating at 48, 56 and 64 kbit/s. Technology of the codec is based on sub-band ADPCM (SB-ADPCM). G.722 sample audio data at a rate of 16 kHz (using 14 bits), double that of traditional telephony interfaces, which results in superior audio quality and clarity. This is useful in fixed network voice over IP applications, where the required bandwidth is typically not prohibitive, and offers a significant improvement in speech quality over older narrowband codecs such as G.711, without an excessive increase in implementation complexity. G.722 patents have expired, so it is freely available. Notes: This is the main codec that broadcasters are familiar with since it has been utilized in ISDN devices for years. Most equipment manufacturers used g.722 as the standard to talk to each other’s devices. G.722 is the clear choice for those who love the sound of ISDN. His codec uses more bandwidth than Speex and CELT.
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	RAW-PCM

	Description: Pulse-code modulation (PCM) is a digital representation of an analog signal where the magnitude of the signal is sampled regularly at uniform intervals, then quantized to a series of symbols in a numeric (usually binary ) code. PCM has been used in digital telephone systems. It is also the standard form for digital audio in computer format. Notes: Using RAW-PCM, audio is sent and received uncompressed. Since no compression takes place, the RAW wav PCM data is sent over the link, real-time. This will sound exactly like the original samples; however, it requires a significant amount of bandwidth. It is mainly used on an internal network or LAN and is not well-suited for the Internet. RAW-PCM is an excellent choice for voice and music.
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	Speex

	Description: Speex is an Open Source/Free Software patent-free audio compression format designed for speech. The Speex Project aims to lower the barrier of entry for voice applications by providing a free alternative to expensive proprietary speech codecs. Moreover, Speex is well-adapted to Internet applications. Speex is based on CELP technology and is designed to compress voice at bitrates ranging from 2 to 44kbps. Speex is well-suited to handle VoIP, internet audio streaming, data archival (like voice mail), and audio books. Notes: The Speex codec is not well suited for music but is the best low-delay, low-bandwidth, voice codec available in Audio CompassTM. This is the default in our software and produces audio from fantastic phone line quality to better than ISDN quality. It is very bandwidth-friendly and is well-suited for the Internet. This codec is perfect for talk show hosts and any remote that is sending voice only.
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	Other

	GSM, G.711,Ilbc,Lpc10 These are older codecs and not recommended for general broadcast use. They are included for compatibility reasons.
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