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

 
AAPL
$111.56
Apple Inc.
+2.15
MSFT
$47.17
Microsoft Corpora
+1.43
GOOG
$506.11
Google Inc.
+1.22

MacTech Search:
Community Search:

Software Updates via MacUpdate

BBEdit 11.0.2 - Powerful text and HTML e...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more
ExpanDrive 4.2.1 - Access cloud storage...
ExpanDrive builds cloud storage in every application, acts just like a USB drive plugged into your Mac. With ExpanDrive, you can securely access any remote file server directly from the Finder or... Read more
Adobe After Effects CC 2014 13.2 - Creat...
After Effects CC 2014 is available as part of Adobe Creative Cloud for as little as $19.99/month (or $9.99/month if you're a previous After Effects customer). After Effects CS6 is still available... Read more
Command-C 1.1.7 - Clipboard sharing tool...
Command-C is a revolutionary app which makes easy to share your clipboard between iOS and OS X using your local WiFi network, even if the app is not currently opened. Copy anything (text, pictures,... Read more
Tidy Up 4.0.2 - Find duplicate files and...
Tidy Up is a complete duplicate finder and disk-tidiness utility. With Tidy Up you can search for duplicate files and packages by the owner application, content, type, creator, extension, time... Read more
Typinator 6.3 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
GraphicConverter 9.5 - Graphics editor w...
GraphicConverter is an all-purpose image-editing program that can import 200 different graphic-based formats, edit the image, and export it to any of 80 available file formats. The high-end editing... Read more
Toast Titanium 12.0.1 - The ultimate med...
Toast Titanium goes way beyond the very basic burning in the Mac OS and iLife software, and sets the standard for burning CDs, DVDs, and now Blu-ray discs on the Mac. Create superior sounding audio... Read more
QuickBooks 2015 16.0.2.1422 R3 - Financi...
Save 20% on QuickBooks Pro for Mac today through this special discount link QuickBooks Pro 2013 helps you manage your business easily and efficiently. Organize your finances all in one place, track... Read more
Remotix 3.0.6 - Access all your computer...
Remotix is a fast and powerful application to easily access multiple Macs (and PCs) from your own Mac. Features: Complete Apple Screen Sharing support - including Mac OS X login, clipboard... Read more

Latest Forum Discussions

See All

Dragon Quest III Review
Dragon Quest III Review By Jennifer Allen on December 18th, 2014 Our Rating: :: DATED BUT NOT WITHOUT MERITUniversal App - Designed for iPhone and iPad A walk down memory lane isn’t foolproof for Dragon Quest III, but it has its... | Read more »
8 KEMCO JRPGs Are Just $0.99 in Celebrat...
8 KEMCO JRPGs Are Just $0.99 in Celebration of the Holidays Posted by Jessica Fisher on December 18th, 2014 [ permalink ] KEMCO has announc | Read more »
Brothers in Arms 3: Sons of War Review
Brothers in Arms 3: Sons of War Review By Jennifer Allen on December 18th, 2014 Our Rating: :: FUN BUT PUSHYUniversal App - Designed for iPhone and iPad Brothers in Arms 3: Sons of War could be great fun, but its plethora of... | Read more »
The Snow is Falling on the French Countr...
The Snow is Falling on the French Countryside of Carcassonne’s Newest Update Posted by Jessica Fisher on December 18th, 2014 [ permalink ] < | Read more »
Creatures Such As We Review
Creatures Such As We Review By Jennifer Allen on December 18th, 2014 Our Rating: :: INTERESTING DISCUSSIONSUniversal App - Designed for iPhone and iPad Taking a more sedate approach to interactive fiction, Creatures Such As We... | Read more »
Stair: Slide the Blocks to Ascend (Game...
Stair: Slide the Blocks to Ascend 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Slide the blocks to ascend! Stair: Slide the Blocks to Ascend | Read more »
Give It Up! (Games)
Give It Up! 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: GIVE IT UP is a rather hard game where you have to assist this cheerful, singing Blob in jumping through 9 different tracks.So far... | Read more »
The Drive : Devil's Run (Games)
The Drive : Devil's Run 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: ON THE ROAD AGAIN! The Drive - Devil’s Run is classic point to point style racing game that pays homage to the classics... | Read more »
Procreate Pocket (Entertainment)
Procreate Pocket 1.01 Device: iOS iPhone Category: Entertainment Price: $2.99, Version: 1.01 (iTunes) Description: Create - anytime, anywhere. Made by the developers of the award-winning Procreate® for iPad®, Procreate Pocket™ allows... | Read more »
IRON FINGER - Mini Games Championship (...
IRON FINGER - Mini Games Championship 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: Quick to play, easy to learn yet hard to master.. TAP, SWIPE & TILT your way through mini games that... | Read more »

Price Scanner via MacPrices.net

KMI MIDI K-Board Great Gift for Amateur &...
The K-Board is a MIDI Nano keyboard for music creation for iPad, Android, And computers; the easiest way to make music with iPads & Android tablets, and Mac, Windows, or Linux computers. Ultra-... Read more
Amazon offers 15-inch 2.2GHz Retina MacBook P...
 Amazon.com has the 15″ 2.2GHz Retina MacBook Pro on sale for $1699 including free shipping. Their price is $300 off MSRP. Stock is limited, so act now if you’re interested. Read more
Holiday sales continue: MacBook Pros for up t...
 B&H Photo has new MacBook Pros on sale for up to $300 off MSRP as part of their Holiday pricing. Shipping is free, and B&H charges NY sales tax only: - 15″ 2.2GHz Retina MacBook Pro: $1699... Read more
Google Search App For iOS Gets A Major Makeov...
Google has given iOS users an early Christmas present with a substantial update of it’s not-very-often-upgraded Google Search app. Google Search has been my go-to tool for Web searches since it was... Read more
ShopKeep Apple Pay And Chip Card Reader Avail...
ShopKeep, a cloud-based technology provider to more than 10,000 small business owners to manage retail shops and restaurants with iPads, has released its new Apple Pay and chip card reader. This... Read more
Holiday sale! 27-inch 5K iMac for $2299, save...
 B&H Photo has the 27″ 3.5GHz 5K iMac in stock today and on sale for $2299 including free shipping plus NY sales tax only. Their price is $200 off MSRP, and it’s the lowest price available for... Read more
Holiday Sale! 3.7GHz Quad Core Mac Pro availa...
 B&H Photo has the 3.7GHz Quad Core Mac Pro on sale for $2599 including free shipping plus NY sales tax only. Their price is $400 off MSRP, and it’s the lowest price for this model from any... Read more
iPhone 6 Number 3 Canadian Google Search Of 2...
CTVNews.ca reports that Apple’s iPhone 6 was the third highest-trending Google Canada search topic of 2014, exceeded only by Robin Williams largely after his death by suicide in August, and the FIFA... Read more
New iPad mini 3 Counter-Top & Wall Mount...
newMacgadgets has announced new secure all-acrylic displays for the iPad mini 3 (also works fine with the mini 2, last year’s iPad mini With Retina Display, and the original iPad mini). The new iPad... Read more
Holiday sales continue, MacBook Airs for up t...
B&H Photo has 2014 MacBook Airs on sale for up to $120 off MSRP, for a limited time, for the Thanksgiving/Christmas Holiday shopping season. Shipping is free, and B&H charges NY sales tax... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.