Mis à jour le 26 February 2019.
Launched in 1997 by Dolby Laboratories, the Dolby Digital multichannel audio format was protected by a patent for 20 years?a patent which has just expired in February 2017. As manufacturers no longer have to purchase a license from Dolby, we should see more audio players offering compatibility with this format. Especially considering that Dolby Digital is still very widely used.
Dolby Digital: what does .1 mean’
The Dolby Digital audio format rose to fame in movie theaters with the release of Batman Returns, before becoming the first multichannel digital audio format available for home screenings, decoded by home cinema amplifiers. Very widely used for DVD-Video discs, the Dolby Digital format contained anywhere from one to six audio tracks coded in 16 bits / 48 kHz. Thanks to an efficient compression codec (AC3), one Dolby Digital 5.1 track offered a data rate of between 384 Kbps and 448 Kbps. In other words, a data rate three to four times less than that of a CD stereo Audio. Precisely 10% of this data is devoted to the LFE track (Low Frequency Effect), which is exclusively dedicated to low frequencies (< 200 Hz). This is the famous .1 of 5.1.
Dolby Digital: the audio format for TV series in 2017
The reduced file size of a Dolby Digital track allows it to be used for broadcasting, and most American TV stations have chosen the AC3 codec to broadcast their TV series. The Sopranos, Six Feet Under and Lost are examples, and these series were broadcast at the turn of the century by HBO in Dolby Digital. Still today, streaming services such as NetFlix and Amazon Prime propose films and TV series with a Dolby Digital audio track. Even multichannel tracks in Dolby True HD format (24 bits, lossless) contain a Dolby Digital 5.1 core (640 Kbps). In short, 25 years after its introduction, Dolby Digital remains a widely used audio format.
Dolby Digital: surround effects come at a price
To decode its six channels, the manufacturer of an amplifier or Blu-ray player must pay for a licence from Dolby Laboratories.
It is said that the licence costs 25,000 dollars the first year a product is commercialized, then 5,000 dollars for the following years. In the case of an Android or iOS software, it is necessary to add 50 cents to 1 dollar per download to this price.
While major players such as Yamaha, Denon and Pioneer don’t have any trouble covering the cost of a Dolby licence, it?s evidently a considerable obstacle for less well-established brands as well as for app developers. Who hasn’t seen his or her favorite video player indicate that it couldn’t read the audio track of a TV series?
It is thus not uncommon for multimedia players to process Dolby Digital by converting it to simple stereo format (downmix), which seems to be ok with Dolby. But in this case, the surround experience loses its luster, while the dynamic compression (Night mode) integrated into true Dolby Digital decoders is also lost.
As such, the expiration of the Dolby Digital patent should allow these manufacturers to propose products which natively decode Dolby Digital audio tracks. The impact could be considerable for devices running the Plex and Emby ecosystems (multimedia server systems), as well as for those running Android and iOS. We can say without a shadow of a doubt that Dolby Digital is a format of the future.