Dolby TrueHD 96kHz Upsampling Improves Blu-ray Audio
Dolby TrueHD with advanced 96kHz upsampling improves the quality of Blu-ray audio and delivers lossless audio with fewer digital artifacts.
This week at the Fidelity Forum, Dolby introduced a new system that takes Blu-ray audio to the next level.
The audio on most Blu-ray discs is sampled at 48kHz. The trouble is that even the original movie tracks are usually only recorded at 48kHz, so once a movie migrates to disc, there isn’t much that can be done.
Dolby’s new system upsamples that audio signal to 96kHz at the master stage prior to the Dolby TrueHD encoding, so you get lossless audio with fewer digital artifacts.
The “fewer digital artifacts” part comes from a feature of Dolby’s upsampling process called de-apodizing, which corrects a prevalent digital artifact known as pre-ringing. Pre-ringing is often introduced in the capture and creation process and adds a digital harshness to the audio. The apodizing filter masks the effect of pre-ringing by placing it behind the source tone - the listener can’t hear the pre-ringing because it’s behind the more prevalent original signal. The apodizing filter was adapted from technology developed by Meridian for audiophile-quality CD players selling for $18,000.
I was able to hear the results of the new upsampling process at Fidelity Forum. During the demo, all the samples sounded fuller, more distinctive and with a better soundstage. What was particularly surprising was the effect of the apodizing filter. I was initially skeptical, because the engineering description of pre-ringing seemed more like jargon, but in practice, I could definitely hear the difference. Higher tones seemed less severe and more natural.
There also seemed to be improvements in the overall ambiance of soundtracks, an airy quality that made the 48kHz versions seem flat. The results can be subtle, but they’re noticeable enough that it is worth it.
There are already home theater components that include built-in upsampling features, but since the Dolby system hits the signal with upsampling before it’s been encoded to TrueHD, the result is closer to the source. Also, other upsamplers won’t do the apodizing filter trick that contributes a lot to the final results.
In order to enjoy the benefits of a 96kHz disc, you need an AV receiver capable of playing it. Generally, newer receivers can, but not all of them. Many new receivers support sample rates up to 192kHz.
Dolby said several mixing houses have already upgraded their systems to take advantage of the new technology. In the US, two new releases Satchurated: Live in Montreal and San Francisco Symphony at 100 will feature the 96kHz soundtracks.
Ideally we’d have Blu-ray discs with audio recorded natively in 96k, but that rarely happens, especially on film titles. Until that becomes more common, Dolby’s solution is a boon for people who value the sound as much as the picture. It’s also a great tool for the enormous back catalog of movies that have yet to be released on Blu-ray, and even more reason to make sure your client’s audio gear is up to date.
Grant Clauser is a technology editor, covering home electronics for more than 10 years for such publications as Electronic House and Dealerscope. He's done ISF-level damage to hundreds of reviewed products and has had audio training from Home Acoustics Alliance and Sencore. Have a suggestion or a topic you want to read more about? Email at [email protected]
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