
Aura: shipping software that was delayed for 4 years because of patent licensing - josephpmay
https://alastairs-place.net/blog/2018/02/21/aura/
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bangonkeyboard
The cherry on top is that in the four year limbo between this software's
completion and release, Apple removed the optical audio port that it requires
to function from all new Macs.

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test6554
It sounds like people have a love-hate relationship with Apple. If you hit the
sweet spot, you are minting money, but they can cut you off at any time by
exercising their control over the ecosystem.

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upofadown
>AC-3, like the competing DTS standard, is a non-optional part of various
other standards, including ATSC, ...

At this point it appears that Dolby has managed to worm its way into the new
ATSC 3 broadcast TV standard as well in the form of something called AC-4.

Dolby started as a tape hiss reduction system that actually was useful. Since
that time it has more and more become just a way to extract license fees from
companies making electronics that involve audio.

For the TV standard they could of just used the open Opus codec, but since the
people who are creating the standards are the ones getting the licensing
revenue there is no real incentive to do something like that. These "industry
standards" have become a kind of a scam.

So no, Dolby is not all that interested in licensing software implementations
of their codecs for random programs. That is simply not where the big money is
and it isn't really their business.

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test6554
I wonder if the big players creating the hardware are part of these patent
collectives and are also receiving some of these licensing fees. That would be
a good way to keep smaller competitors out of an industry.

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Arqu
I work for a rather large company that works with audio and video and we used
Opus but have since switched to a Dolby based audio stack as it offers much
better sound quality, reduced transmission bitrate and is generally more
robust. However this needs a direct involvement with Dolby and not just of the
shelf stuff.

~~~
upofadown
So Dolby has some sort of audio compression method much better than the state
of the art that they are keeping secret? Why would they do this?

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arunoda
I thought this is a "shipping software". But it's a music related app for Mac
(Which seems to be pretty cool).

So, I am thinking this post deserves a better title.

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vortico
Does the optical input for the amplifier _only_ suport AC-3? Why don't
manufacturers use a more naive patent-free method that might be slower? Are
they really starving for bandwidth enough to justify the cost of an AC-3
license? Even uncompressed PCM times 6 channels could easily be transmitted
over USB 2.0, and I was under the impression that these optical formats were
even faster.

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LeoPanthera
Usually the four codecs supported over optical are uncompressed (limited to 2
channels), AC-3, DTS, and MP2.

The patent status of MP2 seems to be hard to determine.

DTS seems to be still patented.

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vortico
Weird, so manufacturers just haven't implemented uncompressed 6-channel
optical audio? Is it bandwidth?

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c2h5oh
Uncompressed stereo 16 bit 44.1khz sample rate (cd quality) is <150 KBps so
it's definitely not bandwidth.

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makomk
It's bandwidth. More specifically, standard TOSLINK only has the bandwidth to
carry stereo audio in uncompressed form. If you want full surround sound it
needs to be compressed to fit into the same bandwidth that stereo audio would
use.

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ComputerGuru
I thought the problem wasn’t toslink (the physical optical layer) but rather
s/pdif (the software layer) which is constrained by its support for the rca
physical layer?

IIRC, toslink 1.0 (circa ‘82 or ‘83) had a limit of 2 or 3 mbps while modern
toslink is well over 100mbps (constrained more by distance than speed).

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DiabloD3
SPDIF is not a software layer, but a limited version of AES3 for consumers. In
the OSI model, AES3 would be considered layer 2.

Layer 2 is not considered software, although it can be performed by software
in systems where such a concept makes sense. However, in AES3, this does not
make sense, and has always been handled in devices via a chip that merely
turns AES3 into I2S to be fed to either a DAC or another interface chip (ex:
conversion between AES PHYs is often done by just bridging the receiver of one
type to the transmitter of another type semi-blindly via I2S).

Also, the AES3 protocol is incredibly simple. It only has a very limited set
of flags (very limited in today's sense, more than enough for what was
intended in 1985, see
[https://en.wikipedia.org/wiki/AES3#Channel_status_word](https://en.wikipedia.org/wiki/AES3#Channel_status_word)
), and was never actually meant to do anything but stereo audio at
conventional rates. Doing encoded bitstreams across it is largely a hack, and
is limited to the base versions of Dolby and DTS.

Using >3mbit over Toslink is not done involving an AES3-purposed PHY, but
instead with other unrelated protocols, such as Digital ADAT. Distance on
typical Toslink is already constrained to about 30 feet.

I have seen other people quote this mythical 100mbit number, but no one has
ever been able to cite such a use in the real world: no standard I have ever
seen that uses Toslink as a PHY has supported such a transmission rate: ADAT
maxes out at around 12mbit, and MADI does not use Toslink at all.

Also, in further irony, in use, I have found unbalanced AES3 (such as via RCA
or BNC) to be more reliable than Toslink; and virtually all of professional
AES3 usage is done by 3 pin XLR because of how unreliable Toslink is...

Although a lot of professionals have moved on from AES3 entirely, and use MADI
or Dante, or don't use digital transmission pipes inside of their studio at
all and run it entirely on a single PC.

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ComputerGuru
Very interesting reply, thank you. I meant to say “protocol layer” rather than
“software layer” but misspoke. The correction is appreciated.

I think I’m going to do some more research on that 100mbps number. Perhaps
they meant Bd/s?

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LeoPanthera
What happens if you connect a Mac to a receiver using an HDMI cable? (And then
chain your monitor to the receiver.)

HDMI can carry uncompressed 7.1 channel audio - will a Mac send that? If it
does, does any playback software support that?

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inopinatus
Yes, just tried it from a 2015 MacBook attached through HDMI dongle to a Denon
AVR. Playback of Dolby test videos and the receiver shows 7.1 audio with
correct perceived sound position. Tested with VLC, Quicktime and Elmedia
player. It's possible the audio stack is remixing on the way through, because
I tried a 5.1 AC3 file as well and receiver was still showing 7.1 _except_
with Elmedia player configured for audio pass-through, upon which it showed
5.1 audio (and issued a noticeable click when the change of format occurred)

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js2
This deserves a better title. HN's title submission rules are going to hurt
chances of it being up voted despite the good story. Something like:

Aura: delayed 4 years by "Reasonable and Non-Discriminatory” licensing

edit: Thank you both folks who replied. I posted this comment, emailed the
mods, then saw your replies. :-)

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dang
Agreed. Thanks! and thanks for the email.

