Audio codecs use noise shaping to improve the overall quality of compressed audio by distributing the quantization noise to frequency bands where it is less perceptible. This technique helps to maintain a balance between reducing the bit rate of the audio signal and minimizing the perceived distortion or artifacts introduced during compression.
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Noise shaping is a technique widely employed in audio codecs to enhance the overall quality of compressed audio. It involves redistributing the quantization noise in a manner that makes it less perceptible to the human ear. By doing so, noise shaping helps strike a balance between reducing the bit rate of the audio signal and minimizing the perceived distortion or artifacts introduced during compression.
One prominent use of noise shaping is in the design of perceptual audio codecs, such as MP3 or AAC, which aim to achieve high compression ratios while maintaining satisfactory audio quality. These codecs rely on psychoacoustic principles, taking advantage of the limitations of human auditory perception to discard or minimize perceptually irrelevant audio information.
To provide a comprehensive answer, let’s delve into some interesting facts surrounding the topic:
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Origin of Noise Shaping: The concept of noise shaping can be traced back to the early 1960s when it was first introduced in digital-to-analog converters (DACs) to improve the audio signal-to-noise ratio.
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Quantization Noise: In digital audio processing, quantization noise occurs due to the finite resolution of the quantization process. It introduces distortions and imperfections that can degrade the audio quality if not handled appropriately.
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Human Auditory Perception: Noise shaping leverages the characteristics of human auditory perception to mask the quantization noise effectively. The human ear is less sensitive to certain frequency ranges and is particularly sensitive to changes in loudness and tonality.
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Noise Shaping Algorithm: Different noise shaping algorithms exist, such as the popular weighted summing algorithm and the psychoacoustic noise shaping algorithm. These algorithms determine the distribution of the quantization noise across the audio frequency spectrum.
To include a quote on the topic, renowned audio engineer and researcher Floyd Toole once stated, “When audio coding research is successful, it produces codecs that transmit sounds that are subjectively transparent.”
Now, let’s illustrate the concept of noise shaping with a simplified example table showing the distribution of quantization noise across various frequency bands:
| Frequency Band | Quantization Noise Level |
|---|---|
| Sub-bass | Low |
| Bass | Moderate |
| Midrange | Low |
| Treble | Very low |
| Presence | Very low |
| Brilliance | Low |
In summary, noise shaping plays a crucial role in audio codecs, helping to enhance compressed audio quality by redistributing quantization noise in frequency bands where it is less perceptible to the human ear. This technique, based on psychoacoustic principles, contributes to maintaining a balance between reducing bit rate and minimizing perceived distortion, ultimately aiming to deliver high-quality audio experiences.
See a video about the subject
Jurgen Harrier, chair of the AES Technical Committee on Audio Coding, discusses an educational package created by the committee to provide information about perceptual audio codecs. Originally released in 2001, the package has been updated and expanded to include new artifact types associated with newer generations of audio codecs. Users can listen to audio examples demonstrating different degrees of severity of these artifacts and explore interactive graphic elements displaying the associated signal spectra. The package can be downloaded from the AES library, free for members and at a nominal fee for non-members.
Here are some additional responses to your query
Noise shaping can help you reduce the perceived noise level of your audio, or enhance the clarity and detail of your audio. Noise shaping is often combined with dithering to achieve the best results.
Real-time audio codecs, like Bluetooth’s SBC, aptX, LDAC, and others, tend to use noise shaping as a form of compression because it’s faster and can be done with lower latency. This type of compression isn’t content-specific like psychoacoustic compression is, but it still abuses the sensitivity of our ears to make compression optimizations.
Noise shapingis a technique typically used in digital audio, image, and video processing, usually in combination with dithering, as part of the process of quantizationor bit-depthreduction of a digital signal. Its purpose is to increase the apparent signal-to-noise ratioof the resultant signal.
More intriguing questions on the topic
What does noise shaping do?
Noise shaping is a technique typically used in digital audio, image, and video processing, usually in combination with dithering, as part of the process of quantization or bit-depth reduction of a digital signal. Its purpose is to increase the apparent signal-to-noise ratio of the resultant signal.
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What is the purpose of dithering?
As an answer to this: Dithering actually improves the audio quality of lower resolution audio by removing quantization distortion and replacing it with white noise. By applying noise, dithering turns the harsh, inharmonic distortion of quantization errors into a low-level, analog-like hiss.
Which noise is useful for dithering?
In reply to that: Which noise is useful for dithering? Explanation: Brown noise is sometimes useful for dithering. Explanation: Capacity of a channel can be increased by increasing channel bandwidth and also by increasing signal power.
Is it necessary to dither?
When Not to Use Dithering. Remember, dither technically adds noise to your signal, so you should avoid using it unless absolutely necessary. You only need to use dither when bouncing a file at a lower bit-depth than it was recorded. You should always apply dither when bouncing a 16-bit file from a 24 or 32-bit mix.
What is noise shaping?
From Wikipedia, the free encyclopedia Digital signal performance enhancement Noise shapingis a technique typically used in digital audio, image, and video processing, usually in combination with dithering, as part of the process of quantizationor bit-depthreduction of a digital signal.
Why are audio codecs important?
As a response to this: The two biggest reasons to be passingly familiar with audio codecs are quality and compatibility. While virtually all audio codecs make files smaller than the original source, some codecs achieve this space-saving by destroying some of the audible sound. This is known as lossy compression, because of the information that is lost in the process.
Which noise shaping algorithm is used in image processing?
A popular noise shaping algorithm used in image processing is known as ‘Floyd Steinberg dithering’; and many noise shaping algorithms used in audio processing are based on an ‘Absolute threshold of hearing’ model. Operation[edit] Noise shaping works by putting the quantization error in a feedbackloop.
How does noise affect audio quality?
Answer: Hiss, static, or background noise increases the audio complexity, which generally reduces the amount of compression which is possible. The more samples available per second, the higher the resulting encoded audio fidelity is likely to be. Increasing the sample rate increases the encoded audio file’s size.