Apparatus and Method for Post-Processing an Audio Signal Using a Transient Location Detection

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This invention describes an apparatus and method for improving the quality of audio signals that have undergone compression, specifically by identifying and processing transient portions (sudden changes like drum hits or note onsets). It reduces or eliminates unwanted artifacts called pre-echoes—which are audio distortions that occur before sharp attacks in compressed audio—and sharpens the attack or impact of transients, thus making the audio sound more natural and clear. The approach works in the time-frequency domain and uses advanced estimation methods to detect and process transients, allowing it to post-process already-compressed (even archived) audio material.

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• Restoration or enhancement of compressed music or audio streams that suffer from pre-echo and attack dulling, such as MP3 or AAC files.
• Improving audio quality in digital broadcasting or streaming platforms (e.g., Spotify, internet radio).
• Restoring archived audio material where original (pre-compressed) files are not available.
• Post-processing in music production to correct compression artifacts after editing or mastering.
• Enhancing speech intelligibility and clarity in low-bitrate telecommunication or voice messaging systems.
• Integration in audio playback devices (e.g., portable music players, smartphones, smart speakers) to improve perceived audio quality on-the-fly.

BenefitsContent extracted from patent full text and abstract with AI.

• Effectively reduces or eliminates pre-echo artifacts, a common annoyance in low-bitrate and block-based encoded audio.
• Amplifies and restores the attack (impact) of transient sounds—making music and audio sound more natural and lively.
• Works as a post-processing solution: can be applied after compression, even to previously archived or distributed files.
• Does not require access to the original uncompressed audio, nor any additional side information from the encoder.
• Frequency-selective: avoids unwanted manipulation of tonal (steady-state) sounds, thus preserving sound fidelity.
• Automated and adaptive: can operate without manual tuning for each individual audio track.
• Can improve overall listener experience by making compressed audio closer to the original, uncompressed quality.

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Patent Abstract

Apparatus for post-processing an audio signal, comprising: a converter (100) for converting the audio signal into a time-frequency representation; a transient location estimator (120) for estimating a location in time of a transient portion using the audio signal or the time-frequency representation; and a signal manipulator (140) for manipulating the time-frequency representation, wherein the signal manipulator (140) is configured to reduce or eliminate a pre-echo in the time-frequency representation at a location in time before the transient location or to perform a shaping of the time-frequency representation at the transient location to amplify an attack of the transient portion.