Apple patent is for bitrate audio encoding
TweetFollow Us on Twitter

Apple patent is for bitrate audio encoding

An Apple patent (number 7895045) for bitrate constrained variable bitrate audio encoding has appeared at the US Patent & Trademark Office. A hybrid audio encoding technique incorporates both ABR, or CBR, and VBR encoding modes.

For each audio coding block, after a VBR quantization loop meets the NMR target, a second quantization loop might be called to adaptively control the final bitrate. That is, if the NMR-based quantization loop results in a bitrate that is not within a specified range, then a bitrate-based CBR or ABR quantization loop determines a final bitrate that is within the range and is adaptively determined based on the encoding difficulty of the audio data. Excessive bitrates from use of conventional VBR mode are eliminated, while still providing much more constant perceptual sound quality than use of conventional CBR mode can achieve. THe inventors are Shyh-shiaw Kuo, Hong Kaura and William G. Stewart.

Here's Apple's background and summary of the invention: "Audio coding, or audio compression, algorithms are used to obtain compact digital representations of high-fidelity (i.e., wideband) audio signals for the purpose of efficient transmission and/or storage. The central objective in audio coding is to represent the signal with a minimum number of bits while achieving transparent signal reproduction, i.e., while generating output audio which cannot be humanly distinguished from the original input, even by a sensitive listener.

"Advanced Audio Coding ('AAC') is a wideband audio coding algorithm that exploits two primary coding strategies to dramatically reduce the amount of data needed to convey high-quality digital audio. Signal components that are "perceptually irrelevant" and can be discarded without a perceived loss of audio quality are removed. Further, redundancies in the coded audio signal are eliminated. Hence, efficient audio compression is achieved by a variety of perceptual audio coding and data compression tools, which are combined in the MPEG-4 AAC specification. The MPEG-4 AAC standard incorporates MPEG-2 AAC, forming the basis of the MPEG-4 audio compression technology for data rates above 32 kbps per channel. Additional tools increase the effectiveness of AAC at lower bit rates, and add scalability or error resilience characteristics. These additional tools extend AAC into its MPEG-4 incarnation (ISO/IEC 14496-3, Subpart 4).

"AAC is referred to as a perceptual audio coder, or lossy coder, because it is based on a listener perceptual model, i.e., what a listener can actually hear, or perceive. The two basic bitrate modes for audio coding, such as AAC, are CBR (constant bitrate) and VBR (variable bitrate). Unlike CBR, in which bitrates are strictly constant at each instance, ABR (average bitrate) allows a small variation of bitrates for each instance while maintaining a certain average bitrate for the entire track, thereby resulting in a reasonably predictable size to the finished files.

"A CBR codec is constant in bitrate along an audio time signal, but variable in sound quality. For example, for stereo encoding at a bitrate of 96 kb/s, an encoded speech track, which is "easy" to encode due to its relatively narrow frequency bandwidth, sounds indistinguishable from the original source of the track. However, noticeable artifacts could be heard in similarly encoded complex classical music, which is 'difficult' to encode due to a typically broad frequency bandwidth and, therefore, more data to encode. CBR is important to bitrate critical applications, such as audio streaming, but the variable sound quality produced makes CBR undesirable for other offline applications.

"A VBR codec is targeted to produce audio having constant quality by using as many bits for encoding as are needed to meet a sound quality target. In other words, the bitrate varies depending on the difficulty associated with encoding a given audio track, with a goal of constant perception of the sound quality along the entirety of the audio stream. With VBR, the sound quality target is typically defined by the Noise-to-Masking Ratio ('NMR'), which is calculated for each block of audio data based on the psychoacoustic model used in the coder. Because the coding bitrate of a VBR codec may vary significantly, VBR is not always suitable for bitrate critical applications.

"Simultaneous Masking is a frequency domain phenomenon where a low level signal, e.g., a smallband noise (the maskee) can be made inaudible by a simultaneously occurring stronger signal (the masker). A masking threshold can be measured below which any signal will not be audible. The masking threshold depends on the sound pressure level (SPL) and the frequency of the masker, and on the characteristics of the masker and maskee. If the source signal consists of many simultaneous maskers, a global masking threshold can be computed that describes the threshold of just noticeable distortions as a function of frequency. The most common way of calculating the global masking threshold is based on the high resolution short term amplitude spectrum of the audio or speech signal.

"Coding audio based on the psychoacoustic model only encodes audio signals above a masking threshold, block by block of audio. Therefore, if distortion (typically referred to as quantization noise), which is inherent to an amplitude quantization process, is under the masking threshold, a typical human cannot hear the noise. A sound quality target is based on a subjective perceptual quality scale (e.g., from 0-5, with 5 being best quality). From an audio quality target on this perceptual quality scale, a noise profile, i.e., an offset from the applicable masking threshold, is determinable. This noise profile represents the level at which quantization noise can be masked, while achieving the desired quality target. From the noise profile, an appropriate coding quantization step is determinable. The quantization step is directly related to the coding bitrate.

"A practical problem with a VBR codec is that the bitrate used to encode some tracks will be either too high (i.e., bits wasted) or too low (i.e., diminished perceptual quality). This phenomenon is due in part to the nature of the track, i.e., the ease or difficulty of encoding the track. However, this phenomenon is mainly due to the fact that current technology has simply not achieved a perfect psychoacoustic model because the understanding of human hearing is still limited. A consequence is inaccurate masking thresholds for targeting sound quality. In addition, the perceived sound quality is not solely dependent on the masking thresholds. Hence, even if a perfect psycho-model existed for generating accurate masking thresholds, the sound quality target derived from the masking threshold (e.g., NMR) still cannot perfectly match what is actually perceived. Based on the foregoing, there is room for improvement in audio coding techniques.

"The techniques described in this section are techniques that could be pursued, but not necessarily techniques that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the techniques described in this section qualify as prior art merely by virtue of their inclusion in this section."

Also, Apple has been granted design patents for the MacBook Pro, iPhone 3G, iPod touch 2G and wireless keyboard.

-- Dennis Sellers

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Adobe InCopy CC 2018 13.0.1.207 - Create...
InCopy CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous InCopy customer). Adobe InCopy CC 2018, ideal for large team projects... Read more
Microsoft Office 2016 15.40 - Popular pr...
Microsoft Office 2016 - Unmistakably Office, designed for Mac. The new versions of Word, Excel, PowerPoint, Outlook and OneNote provide the best of both worlds for Mac users - the familiar Office... Read more
Adobe InDesign CC 2018 13.0.1.207 - Prof...
InDesign CC 2018 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous InDesign customer). Adobe InDesign CC 2018 is part of Creative Cloud.... Read more
Apple iOS 11.1.2 - The latest version of...
iOS 11 sets a new standard for what is already the world’s most advanced mobile operating system. It makes iPhone better than before. It makes iPad more capable than ever. And now it opens up both to... Read more
Slack 2.9.0 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.9.0: Slack now officially, and fully, supports Japanese.... Read more
iExplorer 4.1.9 - View and transfer file...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
PCalc 4.5.3 - Full-featured scientific c...
PCalc is a full-featured, scriptable scientific calculator with support for hexadecimal, octal, and binary calculations, as well as an RPN mode, programmable functions, and an extensive set of unit... Read more
iExplorer 4.1.9 - View and transfer file...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
PCalc 4.5.3 - Full-featured scientific c...
PCalc is a full-featured, scriptable scientific calculator with support for hexadecimal, octal, and binary calculations, as well as an RPN mode, programmable functions, and an extensive set of unit... Read more
Slack 2.9.0 - Collaborative communicatio...
Slack is a collaborative communication app that simplifies real-time messaging, archiving, and search for modern working teams. Version 2.9.0: Slack now officially, and fully, supports Japanese.... Read more

Latest Forum Discussions

See All

Rules of Survival guide - how to be the...
The PUBG craze makes its way to mobile, with more and more battle royale games debuting on iOS and Android. Rules of Survival joins the ranks of mobile PUBG-likes, offering a classic battle royale experiences that doesn't vary too much from its... | Read more »
The best new games we played this week -...
The weekend is upon us friends, and it's time to take a look back and reflect on all of the wonderful games we've played over the past few days. This week was jam packed with new releases. There were some big, long awaited launches, some fun... | Read more »
Lineage II: Revolution guide - tips and...
At long last, Lineage II: Revolution has now come to western shores, bring Netmarble's sweeping MMORPG to mobile devices. It's an addictive, epic experience, but some of the systems in the game can be a bit overwhelming. Here are a few tips to help... | Read more »
A Boy and His Blob (Games)
A Boy and His Blob 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: | Read more »
Fight terrible monsters and collect epic...
Released on Western markets early last month, Dragon Project, created by Japanese developer COLOPL, brings epic monster hunting action to mobile for the very first time. Collect a huge array of weapons and armor, and join up with friends to fight... | Read more »
I Am The Hero (Games)
I Am The Hero 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: I Am The Hero is a pixel art, beat 'em up, fighting game that tells the story of a "Hero" with a glorious but mysterious past.... | Read more »
Kauldron (Music)
Kauldron 1.0 Device: iOS Universal Category: Music Price: $3.99, Version: 1.0 (iTunes) Description: Kauldron is our warmest sounding, punchiest synth yet! A completely new modeling technology, combined with carefully designed... | Read more »
Lineage II: Revolution is mobile’s bigge...
NCSoft’s hit fantasy MMORPG series has just made the leap to mobile with the help of Netmarble in Lineage II: Revolution. With over 1.5 million players having already pre-registered ahead of the game’s launch, Revolution hit the app stores... | Read more »
Swing skilfully in new physics-based pla...
Sometimes it’s the most difficult of obstacles that can be the most rewarding. One game hoping to prove this is OCMO, the new tough but fair platformer from developers Team Ocmo. Primed to set every speedrunner’s pulse racing, as an otherworldly... | Read more »
RPGolf (Games)
RPGolf 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Once upon a time, the kingdom was a land of peace, harmony, and an all-consuming passion for the greatest sport - GOLF. Everyone in the... | Read more »

Price Scanner via MacPrices.net

Early Black Friday sale: Apple iMacs for up t...
B&H Photo has 27-inch iMacs in stock and on sale for up $130-$150 off MSRP including free shipping. B&H charges sales tax in NY & NJ only: – 27″ 3.8GHz iMac (MNED2LL/A): $2149 $150 off... Read more
Apple restocks refurbished Mac minis starting...
Apple has restocked Certified Refurbished Mac minis starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: – 1.4GHz Mac mini: $419 $80 off MSRP – 2.6GHz Mac... Read more
Save on 12″ MacBooks, Apple refurbished model...
Apple has Certified Refurbished 2017 12″ Retina MacBooks available for $200-$240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free.... Read more
Early Holiday sale: 12″ iPad Pros for up to $...
B&H Photo has 12″ iPad Pros on sale today for up to $130 off MSRP. Shipping is free, and B&H collects no sales tax outside NY & NJ: – 12″ 64GB WiFi iPad Pro: $749, save $50 – 12″ 256GB... Read more
Holiday sale prices on Apple 13″ MacBook Pros...
B&H Photo has 2017 13″ MacBook Pros in stock today and on sale for $100-$150 off MSRP, each including free shipping plus NY & NJ sales tax only: – 13-inch 2.3GHz/128GB Space Gray MacBook Pro... Read more
Sale: 13″ MacBook Airs starting at $899, $100...
B&H Photo has 2017 13″ MacBook Airs on sale today for $100 off MSRP including free shipping. B&H charges NY & NJ sales tax only: – 13″ 1.8GHz/128GB MacBook Air (MQD32LL/A): $899, $100 off... Read more
Week’s Best Deal on 13″ MacBook Pros: Apple r...
Apple has a full line of Apple Certified Refurbished 2017 13″ MacBook Pros available for $200-$300 off MSRP. A standard Apple one-year warranty is included with each MacBook, and shipping is free.... Read more
Deal: 15″ 2.6GHz MacBook Pro for $1799 w/free...
B&H Photo has clearance 2016 15″ 2.6GHz Touch Bar MacBook Pros in stock today and available for $600 off original MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: – 15″ 2.... Read more
Black Friday pricing on the 1.4GHz Mac mini....
MacMall has the 1.4GHz Mac mini on sale for $399 including free shipping. Their price is $100 off MSRP (20% off), and it’s the lowest price for available for this model from any reseller. MacMall’s... Read more
Early Black Friday deal: 15″ Apple MacBook Pr...
B&H Photo has 15″ MacBook Pros on sale for up to $200 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 15″ 2.8GHz MacBook Pro Space Gray (MPTR2LL/A): $2199, $200... Read more

Jobs Board

*Apple* Solution Consultant - Apple (United...
# Apple Solution Consultant - Rochester, MN Job Number: 113037950 Rochester, MN, Minnesota, United States Posted: 19-Sep-2017 Weekly Hours: 40.00 **Job Summary** Are Read more
Sr. Experience Producer, Today at *Apple* -...
# Sr. Experience Producer, Today at Apple Job Number: 56495251 Santa Clara Valley, California, United States Posted: 23-Jun-2017 Weekly Hours: 40.00 **Job Summary** Read more
AppleCare Support Engineer for *Apple* Medi...
…Summary AppleCare Engineering, Software & Services, is a group that works to represent Apple 's World Wide contact centers and Apple 's customers to groups within Read more
Site Reliability Engineer, *Apple* Pay - Ap...
Job Summary The Apple Pay Site Reliability Engineering Team is hiring for multiple roles focused on the front line customer experience and the back end integration Read more
*Apple* Solutions Consultant - Apple (United...
# Apple Solutions Consultant Job Number: 86078534 Fairless Hills, Pennsylvania, United States Posted: 07-Jul-2017 Weekly Hours: 40.00 **Job Summary** As an Apple Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.