G.721 is a now obsolete ITU-T recommendation for audio compression and decompression that was superseded by G.726. It was mainly used in telecommunications for ADPCM (Adaptive Differential Pulse Code Modulation), allowing for voice data digitization and transmission. This method enabled a significant reduction in bandwidth usage without a significant loss in speech quality.


The phonetics of the keyword “G.721” would be: “jee dot seven two one”.

Key Takeaways

Main Takeaways About G.721

  1. Compression Technology: G.721 is a form of audio data compression technology most commonly found in telecommunication. It was specifically created by the International Telecommunications Union (ITU-T) to handle adaptive differential pulse code modulation (ADPCM) which sustains sound quality while decreasing data sizes.
  2. Bandwidth Efficiency: G.721 is designed to transmit high-quality audio over digital lines at a lower bitrate than original . Pcm resulting in better bandwidth usage. It operates at a 32 kbit/s bitrate, allowing for an improved efficiency in data transmission while maintaining high-grade audio quality.
  3. Superseded Standard: Despite its effective role in audio compression, the G.721 has been officially withdrawn by the ITU-T. The principles of the G.721 standard, however, have been incorporated into the broader G.726 standard which continues to be used today.


G.721 is a significant term in technology as it refers to a standard for audio compression used extensively in telecommunication. Developed by ITU-T (International Telecommunication Union – Telecommunication Standardization Sector), G.721 uses Adaptive Differential Pulse Code Modulation (ADPCM) for compressing audio data, specifically for digital transmission of voice signals. It performs this compression at a 32 kbit/s bitrate, thus conserving data bandwidth while ensuring a relatively high quality of sound transmission. The advent of this standard considerably improved the efficiency of voice data transmission over digital networks, marking it as an important milestone in the evolution of telecommunications technology.


G.721 is a technology term associated with telecommunication and data compression. It refers to a specific standard for voice compression developed by the International Telecommunication Union. It was devised to maximize the efficiency of voice data transmission, making it crucial for improving overall performance of telecommunications networks, especially in scenarios that demand high-quality voice communications over digital networks.G.721 uses ADPCM (Adaptive Differential Pulse Code Modulation) for its operation, which enables it to convert analog signals into digital signals fit for transmission over digital telecommunication networks. Thanks to this compression mechanism, G.721 efficiently reduces the amount of data needed for voice transmission, allowing a higher number of voice channels to be sent over the same network capacity, thus optimizing bandwidth. However, it’s critical to note that G.721 has been obsolete for a while and has been replaced by G.726, which offers more sophisticated data compression techniques.


G.721 is actually not a valid or recognized technology term. However, if you’re referring to G.721 as an older or incorrect point of reference to audio codec standards used in digital and voice data compression, it might be a confusion with G.711 or G.721. Here are examples referring to G.711:1. VoIP Phone Calls: G711 is commonly used for VoIP (Voice over Internet Protocol) phone calls, allowing digital transmission of voice data over the internet, thus improving call quality and reducing costs.2. Teleconferencing Systems: Many teleconferencing or video conferencing systems utilize G711 to ensure high-quality audio data transmission.3. Online Gaming: Voice chat in online gaming may also use G711 for real-time communication among players. Please note that these examples refer to G.711 since G.721 is not a recognized term. If you are referring to a different technology, please provide a more specific or correct term.

Frequently Asked Questions(FAQ)

Q: What is G.721?A: G.721 is a standard for audio companding. It is an adaptive differential pulse code modulation (ADPCM) developed by ITU-T. Previously widely used in digital telephony, its functionality has been deprecated and it was superseded by other better algorithms.Q: What does G.721 do?A: G.721 helps to reduce the data rate required for audio signals, by converting 16-bit linear PCM samples into a 32 kbit/s bitstream.Q: How does G.721 work? A: G.721 works on the adaptive differential pulse code modulation method. It predicts a future value and stores only the variance from that prediction – which requires less data.Q: Is G.721 still widely used today?A: No, G.721 is no longer widely used as it has been mostly replaced by newer and more efficient codecs such as G.729.Q: What are comparable alternatives to G.721?A: Comparable alternatives to the G.721 coding scheme include newer standards G.729, G.726, and G.722.Q: What is the bit rate of G.721?A: The bit rate of G.721 is 32 kbit/s. Q: How does G.721 affect the quality of an audio signal?A: Although G.721 decreases the data rate of an audio signal, the main goal is to maintain the quality of the signal. Any changes in quality would be minimal and generally undetectable to the human ear. Q: What are the advantages of using G.721?A: The main advantage of using G.721 is the reduced bandwidth and storage requirements due to its efficient compression technique. It was particularly beneficial during its heydays when bandwidth and storage were more limited and expensive as compared to today.Q: In which applications is G.721 commonly used?A: G.721 was primarily used in digital telephony. However, it is no longer widely used as it has been replaced by newer and more efficient standards.

Related Tech Terms

  • Bit Rate Reduction
  • Audio Data Compression
  • International Telecommunication Union
  • Telephony
  • ADPCM (Adaptive Differential Pulse Code Modulation)

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