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Bob Adams Upsampling — Can You Really Change the Past?
While the music industry has always been pushing new, higher resolution formats, what does that do to folks like us who have a ton of content in the old format? One of our 3rd party developers has developed a technique that allows existing "standard" CDs to have the enhanced audio clarity, richness and dynamic range that would normally be associated with SACD or DVD-A disks, "upgrading" the tremendous investment that you've already made in high quality CD recordings. Q5™ Upsampling from ANAGRAM Technologies, of Switzerland, allows digital audio signals from virtually any audio source to be resampled, resynchronized and retimed to extraordinary levels of detail. In effect, upsampling the digital data stream (up to 384kHz). Upsampling: How it Works ANAGRAM Q5's software-based architecture supports pulse code modulation (PCM) and DSD decoding (through its DSF™ Filtering technology) for compatibility with CD, DVD, and SACD formats. It provides ultra-low jitter due to its local high-precision clock and clock synchronization within the Q5 technology. Plus, the 384kHz, 8xFs (or higher) output sampling rate allows the bypass of the DAC chip's internal over-sampling filter for best-in-class audio performance. Three proprietary ANAGRAM technologies are included in Q5: adaptive time filtering, data-to-system synchronization, and virtual time-domain model. These technologies effectively reduce noise artifacts caused by imperfect digital systems and allow the digital signal to closely represent the true analog sound of the studio mastered audio data. Furthermore, by leveraging powerful yet low cost DSP architectures ANAGRAM allows the average audio consumer to benefit from these state-of-the-art audio technologies. Adaptive time filtering allows the system to adapt to small fluctuations in the system's audio master clock. The master clock is the heart of any digital audio system, however as with all components that are constructed from physical materials, they will at some point in time deviate from their ideal generalized behavior causing, in this case, variation in frequency and system jitter in this important internal timing reference. Typically these variations will not be corrected for, however in Q5 enabled devices the system automatically adapts to these small fluctuations, resulting in "glitch" free analog sound even after endless hours of continuous playback. Data-to-System synchronization allows any incoming audio stream to be resynchronized and retimed to a local high quality clock. By using a stable clock reference, the negative effects of inter-component jitter can be minimized. When converting the digital audio to an analog signal through high performance D/A converters, this reduction in jitter has enormous benefits in the level of detail and clarity in the reconstructed analog sound. Combining this process with a virtual time domain model that uses an advanced cubic interpolation algorithm to resample the incoming audio data, timing errors in this signal can be compensated for at amazing levels of accuracy. The end result is tighter, more focused bass, increased stereo imaging, focus and separation for all musical instruments and voices. Anagram has developed this technique for our Blackfin Processor, and this technology will soon be seen (and heard) on several new CD players, just in time for the Christmas season!
Bob Adams is a Manager of Audio Technology at Analog Devices. His column appears here regularly. |
For this month's column, I'd like to present a guest editorial from Paul Wheeler, ADI's Segment Business Manager, Digital Home