Audio Post-Processing - Ittiam Systems

Audio Post-Processing

Audio Post-Processing

In the age of personalized-audio, device makers are wise to offer a range of audio experiences from the same device. Ittiam plays an important role in ensuring that your audio attunes to your ear.

Ittiam Audio Effects is a suite of audio post processing algorithms that enables users to personalize audio to their preferences for a rich listening experience. These algorithms, with superior sound quality, low memory footprint and processor loading, are specially suited for portable audio players and mobile phones.

The software suite includes the following components:

  • Bass and Treble Control: Low and high frequency enhancement
  • Graphic Equalizer: Spectrum control of audio with presets
  • Parametric Equalizer: Complete parametric control of audio band spectrum
  • Sample rate converter: Change the sampling rate of a discrete time signal
  • Stereo Widening: Sound image expansion and externalization for headphone and speaker playback
  • Reverb: Wide range of room effects for different listening environments
  • DRC: Dynamic Range Control suitable for audio and speech
  • Peak Limiter: Transparent clipping prevention in the output signal
  • Virtual Surround

Ittiam provides a complete suite of Audio Effects for portable music players and mobile phones. These post processing effects enhance the listening experience while reducing listening fatigue. Ittiam’s post processing IPs produce superior quality audio, which is achieved by optimization targeted at power footprint and low CPU utilization. Our IPs are supplemented with audio, video and system software to provide cost- and time-to-market advantage.

Graphic Equalizer is a set of filters that modifies the frequency envelope of an audio sample. Each filter controls a fixed range of audio frequencies. The gain for each band can be controlled using sliders which are provided for each band (filter).

  • Gain in the range of -12 dB to +12 dB for each band
  • Number of bands is configurable to a maximum of 10
  • The center frequency for each band can be statically configured during initialization

Parametric Equalizer is a set of filters that modifies the frequency envelope of audio with controls for the center frequency (f0), the bandwidth (BW) and the gain (G) for each band to be varied by the user.

  • Number of bands is configurable
  • Gain in the range of -18 dB to +18 dB
  • Q factor from 0.5 to 3
  • Center frequency from 20 Hz to fs/2 kHz
  • Constant Q maintained for any gain setting

While listening to music over headphones, a sound image is created inside the listener’s head. This causes listening fatigue. The Stereo Widening component uses psychoacoustics to create the sound image outside the listener’s head. This makes listening to music over headphones a comfortable and pleasant experience, avoiding listening fatigue.

Stereo Widening can also be used for loud speaker playback to expand the sound image by creating virtual speakers at a wider angle with respect to the listener.

  • Configurable position of virtual speakers in the range of 0 to 90 degrees with respect to the listener
  • Support for both headphones and speakers
  • Configurable position of the actual speakers for speaker playback
  • ‘Out Of Head’ sound image for headphone playback to reduce listening fatigue
  • Wide sound image for loudspeaker playback

Reverberation refers to sounds reflected from the walls and other surfaces in an enclosure such as a room or a hall. This is what makes a small room ‘sound’ different from a large hall. When a sound source generates a sound, it reaches the ear directly (direct sound) and also after bouncing off the walls and the ceilings. These reflected sounds increase in density from sparse echoes (early reflections) to highly dense echoes (late reverb) over time.

The Ittiam Reverb algorithm simulates many different listening environments and can be enabled with presets for a concert hall, a large room, a medium room, a small room and a plate reverb.

Peak Limiters are used in the audio chain to provide an upper limit to the peak value of the audio content without introducing any distortion due to clipping. Signals exceeding the user defined limit are intelligently processed to bring them within the limit in such a fashion that the operation is transparent to the listener. Peak limiters are typically used in audio CD mastering, sound mixing or as  an alternative to the saturation logic in any audio processing chain.

  • True Peak Limiting Operation: Clipping does not occur irrespective of the signal dynamics
  • Transparent Operation
  • Configurable Threshold Level

Sample Rate Converter is an algorithm that changes sample rate of audio. Applications include portable media players, mobile phones, broadcast, automobile audio systems etc.

  • Supports conversion between arbitrary sample rates (ratio 6:1 to 1:6)
  • Supports mono/stereo/multichannel file re-sampling
  • 16 or 32 bit input and output
  • Quality of algorithm is configurable based on the use case

DRC (Dynamic Range Control) reduces the dynamic range (range of audio level variation from lowest to the highest level) of audio, by increasing the level of soft passages and decreasing the level of loud sections in the audio content.

DRC addresses the problem of listening to music in the presence of ambient noise, for instance in a crowded street or a railway station. In such noisy environments, if the volume is set low, the soft passages will be drowned in the ambient noise and an increase in volume will make the loud sections annoying. With DRC, the listener can enjoy music even in a noisy environment without having to touch the volume control. DRC also enables the listener to watch sci-fi/action movies in very quiet environments without disturbing others.

  • Supports configurable threshold levels

Virtual Surround technology enables the listener to enjoy 5.1 multi-channel content over headphones or two speakers. Down mixing of multi-channel audio to 2 channels by simple matrixing results in a loss of spatial information embedded in the multi-channel content.

Virtual Surround, on the other hand, uses sophisticated signal processing to create an illusion that the sound is emanating from 5 speakers around the listener either while listening over headphones or two speakers.

  • Support for both headphones and speakers
  • Preservation of timbre of the original recording
  • ‘Out of Head’ sound image for headphone playback to reduce listening fatigue
  • Bass Management (optional)

Graphic Equalizer

Graphic Equalizer is a set of filters that modifies the frequency envelope of an audio sample. Each filter controls a fixed range of audio frequencies. The gain for each band can be controlled using sliders which are provided for each band (filter).

  • Gain in the range of -12 dB to +12 dB for each band
  • Number of bands is configurable to a maximum of 10
  • The center frequency for each band can be statically configured during initialization

Parametric Equalizer

Parametric Equalizer is a set of filters that modifies the frequency envelope of audio with controls for the center frequency (f0), the bandwidth (BW) and the gain (G) for each band to be varied by the user.

  • Number of bands is configurable
  • Gain in the range of -18 dB to +18 dB
  • Q factor from 0.5 to 3
  • Center frequency from 20 Hz to fs/2 kHz
  • Constant Q maintained for any gain setting

Stereo Widening

While listening to music over headphones, a sound image is created inside the listener’s head. This causes listening fatigue. The Stereo Widening component uses psychoacoustics to create the sound image outside the listener’s head. This makes listening to music over headphones a comfortable and pleasant experience, avoiding listening fatigue.

Stereo Widening can also be used for loud speaker playback to expand the sound image by creating virtual speakers at a wider angle with respect to the listener.

  • Configurable position of virtual speakers in the range of 0 to 90 degrees with respect to the listener
  • Support for both headphones and speakers
  • Configurable position of the actual speakers for speaker playback
  • ‘Out Of Head’ sound image for headphone playback to reduce listening fatigue
  • Wide sound image for loudspeaker playback

Reverb

Reverberation refers to sounds reflected from the walls and other surfaces in an enclosure such as a room or a hall. This is what makes a small room ‘sound’ different from a large hall. When a sound source generates a sound, it reaches the ear directly (direct sound) and also after bouncing off the walls and the ceilings. These reflected sounds increase in density from sparse echoes (early reflections) to highly dense echoes (late reverb) over time.

The Ittiam Reverb algorithm simulates many different listening environments and can be enabled with presets for a concert hall, a large room, a medium room, a small room and a plate reverb.

Peak Limiter

Peak Limiters are used in the audio chain to provide an upper limit to the peak value of the audio content without introducing any distortion due to clipping. Signals exceeding the user defined limit are intelligently processed to bring them within the limit in such a fashion that the operation is transparent to the listener. Peak limiters are typically used in audio CD mastering, sound mixing or as  an alternative to the saturation logic in any audio processing chain.

  • True Peak Limiting Operation: Clipping does not occur irrespective of the signal dynamics
  • Transparent Operation
  • Configurable Threshold Level

Sample Rate Converter

Sample Rate Converter is an algorithm that changes sample rate of audio. Applications include portable media players, mobile phones, broadcast, automobile audio systems etc.

  • Supports conversion between arbitrary sample rates (ratio 6:1 to 1:6)
  • Supports mono/stereo/multichannel file re-sampling
  • 16 or 32 bit input and output
  • Quality of algorithm is configurable based on the use case

DRC

DRC (Dynamic Range Control) reduces the dynamic range (range of audio level variation from lowest to the highest level) of audio, by increasing the level of soft passages and decreasing the level of loud sections in the audio content.

DRC addresses the problem of listening to music in the presence of ambient noise, for instance in a crowded street or a railway station. In such noisy environments, if the volume is set low, the soft passages will be drowned in the ambient noise and an increase in volume will make the loud sections annoying. With DRC, the listener can enjoy music even in a noisy environment without having to touch the volume control. DRC also enables the listener to watch sci-fi/action movies in very quiet environments without disturbing others.

  • Supports configurable threshold levels

Virtual Surround

Virtual Surround technology enables the listener to enjoy 5.1 multi-channel content over headphones or two speakers. Down mixing of multi-channel audio to 2 channels by simple matrixing results in a loss of spatial information embedded in the multi-channel content.

Virtual Surround, on the other hand, uses sophisticated signal processing to create an illusion that the sound is emanating from 5 speakers around the listener either while listening over headphones or two speakers.

  • Support for both headphones and speakers
  • Preservation of timbre of the original recording
  • ‘Out of Head’ sound image for headphone playback to reduce listening fatigue
  • Bass Management (optional)
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Datasheets

Ittiam Audio Mixer
Ittiam Bass & Treble filters
Ittiam Sample Rate Converter
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