This is how MP3 compression came into the world.A psychoacoustic model is applied to digital media, and determines what can be deleted to save space without a noticeable loss of sound quality. Psychoacoustics studies how humans perceive sound.This is because the further you get from the source, the more interference from physical barriers (e.g., walls, objects, people) and overlapping radio frequencies (e.g., microwaves, Wi-Fi signals). Bluetooth devices have an assigned range (typically 10 meters for headphones).This is calculated by multiplying the sample rate by the bit-depth. Bit rate (kbps or Mbps): the amount of audio data transferred per second.A greater bit depth multiplies the file size. CD-quality is 16-bit, but high-resolution files extend this to 24-bit. A higher bit depth records a signal more accurately. Bit depth (-bit): the number of digital bits used to represent each audio sample.A greater sample rate means a greater file size. “High-resolution” file formats are considered to be 96kHz or greater. You need at least two samples per cycle for a digital signal to represent any given frequency, so audio is typically sampled at a rate of 44.1kHz-approximately twice the upper limit of human hearing (20kHz). Sample rate (Hz): the number of points of data per second in an audio file.Journaline(R) is the enhanced text application of DRM and DAB(+) - a mandatory part of EWF, the Emergency Warning Functionality. AAC FAQ>įor Digital Radio Mondiale (DRM) compliant products, the AAC license available from Via covers implementations of xHE-AAC (Extended High-Efficiency AAC) audio codec in addition to HE-AAC v2 which are mandated by the DRM technical specification. In this way the AAC family with its latest enhancement, xHE-AAC can support a wide variety of applications ranging from extremely low bit-rates required for reliable speech and music delivery over 2G cellular phone networks, to “transparent” quality (indistinguishable from the original source material) for the most discriminating listeners.Īdditional AAC technologies covered by the patent license include AAC-LD (Low Delay), AAC-ELD (Enhanced Low Delay) and AAC-ELD v2, which enable high quality audio for videoconferencing or other communications applications where low-latency performance is critical.įor additional information about Via LA’s AAC patent licensing program, please see our FAQ (Frequently Asked Questions) page. For example, MPEG-4 AAC-LC (Low Complexity) decoders can playback MPEG-2 AAC-LC bit-streams, MPEG-4 HE-AAC (High Efficiency) decoders can playback both MPEG-4 and MPEG-2 AAC-LC bit-streams, etc. The core of this AAC family is a set of backwards-compatible audio coding technologies. The AAC patent licensing program provides coverage for all the AAC technologies identified in the following diagram. Via LA administers a joint patent license which provides a convenient and cost-effective way to acquire the rights to practice the essential AAC patents from a set of licensors. Interactive Demonstration of xHE-AAC Audio Quality xHE-AAC adds an optimized speech coding approach to the AAC family of codecs, resulting in a single audio coding system capable of maintaining exceptional quality starting at very low bit-rates with any type of program content, whether speech, music, or ambient sounds. Most recently, MPEG standardized the latest AAC enhancement xHE-AAC (Extended HE-AAC). The original MPEG-2 AAC codec was further refined through the MPEG-4 standardization process and has subsequently been enhanced with bandwidth extension technology yielding HE-AAC (High Efficiency AAC), and with the addition of parametric stereo, resulting in HE-AAC v2. Standardized by ISO MPEG, it is designed to provide high quality audio at lower bit-rates than previous MPEG audio coding formats. The AAC family of audio codecs comprises some of the most efficient audio coding technologies available today.
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