Dolby® Upsamples & Apodizes TrueHD
At 12 noon PST today, Dolby Laboratories, Inc. announced the availability of the first Blu-ray Discs premastered using Dolby® TrueHD with advanced 96k upsampling, The process, designed for use by studios, authoring houses, and mastering facilities, elevates playback performance of lossless audio on Blu-ray Disc by using the apodizing filter developed by Meridian.
Dolby TrueHD, whose white paper can be found here, has already been utilized to upgrade the sound in Greater China's release of The Flowers of War; the Joe Satriani concert film, Satchurated: Live in Montreal; and San Francisco Symphony at 100. The latter, a wonderful memento of San Francisco Symphony's Centennial Opening Night Gala, includes Michael Tilson Thomas conducting performances of Copland's Billy the Kid Ballet Suite, Mendelssohn's Violin Concerto in e with no less a fiddler than Itzhak Perlman, Britten's The Young Person's Guide to the Orchestra, and a multi-media version of Adams' thrilling Short Ride in a Fast Machine.
As Stereophile's representative at Dolby's two-day Fidelity Forum 2.0, where I rubbed shoulders with Rob Sabin, Editor-in-Chief of Stereophile's brother publication, Home Theater, and 19 other members of the international press, I had the opportunity to experience first-hand the difference that Dolby TrueHD makes. In an opening session, the overseer of the project, Dolby Labs' Craig Eggers, Director, Content Creation and Playback, Home Theater Ecosystem, explained that most studio content is recorded at 48kHz, whose preringing artifacts are audible and degrade sound. Even though manufacturers of better Blu-ray players often include upsamplers in their products to clean up the pre-ringing in 48kHz content and provide a smoother presentation, their solutions are, at best, only partial fixes.
Given that there are already multitudes of cheap Blu-ray players in people's homes that do an outstanding job of transmitting, if not amplifying every preringing artifact on a Blu-ray disc, the thought of trying to convince consumers to upgrade those under $100 players seemed futile. Instead, Dolby set out to develop a method by which they could improve Blu-ray sound in the discs themselves by upsampling those that had been recorded at a native 48kHz sample rate to 96kHz.
Their model was the advanced apodizing upsampling filter, employed in the Meridian Audio 808.2 CD player (now succeeded by the 808.3), which inspired John Atkinson to declare, "Without any hyperbole, ...I can say that the Meridian 808i.2 is the finest-sounding CD player I have yet heard."
Thanks to a process developed in part by Dolby scientist Rhonda Wilson, a DSP specialist formerly of Meridian, with 48kHz-sampled masters, the Dolby TrueHD media producer masks preringing artifacts introduced upstream by analog-to digital converters' linear-phase brickwall filters. Dolby TrueHD shifts the artifacts into postringing, which will be naturally masked.
Eggers summarizes the process thusly in Dolby's press release: "Lossless audio is a key distinguishing feature of Blu-ray content. All things being equal, you cannot improve on the quality of lossless audio coding; however, you can improve on the quality of the source PCM content prior to lossless encoding, and this is precisely what we have achieved with our advanced 96k upsampling technology....Studios and authoring facilities that implement Dolby TrueHD with advanced 96k upsampling can elevate the quality of PCM audio prior to lossless Dolby TrueHD encoding, ensuring that consumers get the very best audio performance possible from their Blu-ray playback systems."
In a session presented by Dolby Labs' James Spezialy, Senior Application Engineer, Indirect Film Services, we heard side-by-side clips that compared Blu-ray's standard 48k sound with 96k Dolby TrueHD.
At the start of the comparison, Dolby distributed an "ear training" sheet that included tips on what to listen for. The list, which read like Audiophile 101, included "clarity and naturalness to sound, longer 'ring out' to reverb and ambience, consistent audible quality as high frequencies decay, better definition between instrumentation, and more natural-sounding dialogue with a less granular quality to voices."
As impressive as were the differences in clips from the Joe Satriani concert, Lost Bladesman, Batman Returns, Kung Fu Panda, and Flowers of War, the most telling comparison came via a 27 second, audio-only clip from the San Francisco Symphony. Heard via Bryston amplification, a Revel multi-channel loudspeaker set-up that included subwoofers, and generic cabling that I felt was the system's weak point, instrumental timbres sounded truer and more complete, with a more lifelike sense of natural reverberation and decay. In the switch to Dolby TrueHD 96k, an overall flatness of the 48k symphonic presentation ceded to a far more involving sense of air and space.
As someone who attended San Francisco Symphony's Centennial Gala, and knows the sound in Davies Symphony Hall from any number of premiere and not-so-premiere seats, I felt that Dolby TrueHD took me one step closer to being there. And while I may not wish to get any closer to Kung Fu Panda or his opponents, I'll gladly cuddle up to the sound of Perlman's violin or San Francisco Symphony's strings anytime I can. From what I've heard of Dolby TrueHD, the process succeeds in doing exactly what Dolby and Meridian intended.
Blu-ray discs mastered with the apodizing filter will be labeled "Advanced 96k Upsampling."