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Multichannel audio is increasingly ubiquitous in consumer audio applications such as surround sound playback systems and multichannel audio streaming. These applications often present challenging bandwidth constraints making parametric multichannel coding schemes attractive. A novel low bit rate five channel encoding system called the Immersive Soundfield Rendition (ISR) System has been developed by ATC Labs which emphasizes accurate reproduction of multi-band temporal envelope.
Superior Audio Quality : Surround image fidelity superior to its market peers
Flexibility : Easy integration and deployment with any stereo codec to yield an integrated multichannel coding scheme.
Efficient Compression : Several innovative strategies for efficient compression such as joint inter-channel envelope coding, differential coding in tandem with adaptive Huffman coding.
Technology Highlights :
Analysis and encoding of accurate multi-band temporal envelope. The envelope is computed by analyzing the signal using an over-sampled, high resolution Utility Filter Bank (UFB) and computing a suitable time-frequency envelope based upon a signal adaptive resolution. A slew of efficient coding techniques are then employed to jointly encode the multi-channel time-frequency envelopes
Mechanism to create acoustic diversity between the front and surround channels; e.g., if an instrument (or vocal) with a detectable harmonic pattern is present only in the front channels it is removed from the downmix using accurate tone detection and subtraction techniques before generating the surround channel
Mechanism for estimating and incorporating suitable time delays between the front and surround channels.
Use of a new phase compensated stereo down-mixing scheme. The scheme compensates phases in the ODFT domain using an adaptive estimation algorithm
A new blind 2-to-5-channel up-mixing algorithm which emphasizes the enhancement of any detected smooth image movements in the stereo downmix to generate a high level of recreated spaciousness
Configurable Modes of Operation :
Chandresh Dubey, Richa Gupta, Deepen Sinha and Anibal Ferreira, “A Novel Very Low Bit Rate Multi-Channel Audio Coding Scheme Using Accurate Temporal Envelope Coding and Signal Synthesis Tools”, in the preprints of 121st AES Convention October 5-8, 2006 San Francisco, CA, USA...Pdf
Chandresh Dubey, Raghuram Annadana, Deepen Sinha and Anibal Ferreira, “New Enhancements to Immersive Sound Field Rendition (ISR) System”, in the preprints of 122nd Convention 2007 May 5-8, Vienna, Austria...Pdf
Chandresh Dubey, Raghuram Annadana, Deepen Sinha and Anibal Ferreira, “Subjective Evaluation of Immersive Sound Field Rendition System and Recent Enhancements”, in the preprints of 123rd Convention 2007 Oct 5-8, New York, USA...Pdf
Mode 1 : Detailed multi-channel reproduction with 12- 14 kbps overhead; including a 12 kbps Constant Bit Rate (CBR) option.
Mode 2 : High quality multi-channel reproduction with 8-10 kbps overhead; including an 8 kbps CBR option.
Mode 3 : Realistic multi-channel reproduction with 4-6 kbps as overhead; including a 6 kbps CBR option.
Mode 4 : Blind/Near Blind upmixing with a 0-2 kbps overhead.