New standard for audio: AC-4

[Pixar]

Released by ETSI: http://www.etsi.org/news-events/news/783-2014-04-etsi-releases-ac-4-the-new-generation...codec-standard

Promises, promises

• Intelligent Loudness: Fully automated loudness management means more precise control and eliminates problems with cascaded processing. It acts across a wide range of devices and applications (home theatre to mobile) and can be configured to align with numerous worldwide standards and/or recommendations.
• Advanced Dialogue Enhancement: End-users can have control of the dialogue level in relation to other sounds in the programme - suiting individual hearing needs and preferences.
• Advanced Accessibility: Service providers can easily and efficiently deliver secondary audio in 5.1 surround sound for the visually impaired without doubling the file size or bitrate.
• A/V Frame Alignment: AC-4 is the first emission audio format that allows the audio frame sizes to precisely match the video frame size. This allows the AC-4 data stream to be edited/spliced at video frame boundaries to maintain synchronization without the need to decode and re-encode the audio.
• Bandwidth Efficiency: AC-4 utilizes state-of-the-art compression techniques that provide significant bandwidth savings or higher quality in stereo and surround sound

Spec here if you want to dive deep: http://www.etsi.org/deliver/etsi_ts/103100_103199/103190/01.01.01_60/ts_103190v010101p.pdf

Love Facebook? Here: https://www.facebook.com/etsi.standards/posts/525213184255690

I did't find any manufacturer commitments with a quick search. If you know, please post.

[jman98]

Basically it seems to me to be a solution in search of a problem. We'll see if it gets adapted or ignored.

[Pixar]

Weeell, let's see. ETSI is not completely clueless. The standard called GSM did quite well...as did the WCDMA 3G...

A/V Frame Alignment - seems useful, at least I have noticed the problem, time and time again. Provided it works.

Bandwith efficiency - well, many at ETSI have wireless/mobile background so I'm sure they are trying to push boundaries there for acceptable quality VS bandwith use. Others have identified the problem too, so adaptation counts!

[jman98]

Weeell, let's see. ETSI is not completely clueless.

That's NOT what I said. Or implied. Why do you care so much anyway? Do you have money invested in this, strange new guy who joined us only to talk about this? Again, it's a solution in search of a problem. Oh how poor we all are that for all these years those terrible terrible problems this solved were things we just had to live with. Or not. Time will tell.

[Pixar]

I feel welcome already. You do know that it is possible to have another opinion than you on what is a problem and what is not? My experience tells me one thing, your says another. Fine. But remember that most things you take for granted now, you probably did not know you wanted until someone offered it to you. That's how innovation works.

I was trying to have a friendly argumentation, nothing more. Time, will tell, agree. Technology comes second to the deals you can cut anyway. That's why I put out the question on adaptation.

And No, I don't have any money invested here - only 29 years of experience from the mobile industry, in a sense I have invested a lot of time perhaps.

[yoda313]

About that last bit there about bandwidth efficiency - isn't that what dolby digital plus is for? That's what vudu and others use for 5.1 streaming online.

And also - will this be fully backwards compatible with ac3 and doable over fiber optic? It means nothing to me if you have to go hdmi to get the benefits.

I haven't really seen the need to jump to hdmi as my sd amps are just fine. I'd like to someday but it still isn't a compelling reason to upgrade for me even though I love new or better tech.

[jman98]

About that last bit there about bandwidth efficiency - isn't that what dolby digital plus is for? That's what vudu and others use for 5.1 streaming online.

And also - will this be fully backwards compatible with ac3 and doable over fiber optic? It means nothing to me if you have to go hdmi to get the benefits.

I haven't really seen the need to jump to hdmi as my sd amps are just fine. I'd like to someday but it still isn't a compelling reason to upgrade for me even though I love new or better tech.

Go to http:/www.woot.com and join their daily mailing list. A few times a year they have a big time sale on an HDMI compatible receiver. I bought one made by Denon. The price savings are huge - I paid maybe $150 for mine a couple of years ago if I remember correctly. Note that Woot sales are ONE DAY ONLY. And they have limited quantities, so if you delay, like maybe you wait until you get home from work to do the purchase, they may be sold out. They also sell refurbished Roku 3 models from time to time at a big cost savings over the normal price, but those sell out within hours.

The Denon replaced a completely useful and functional Pioneer receiver that lacked HDMI inputs. When I bought the Pioneer, I searched and NOBODY anywhere was making receivers at the time with HDMI inputs. It wasn't that they were expensive, it was that they didn't exist. Less than 1 year after I bought the Pioneer, everybody starting coming out with HDMI inputs on affordable receivers. I was so pissed off. Eventually I gave the Pioneer to a friend and bought the Denon because it really simplified things to be able to use HDMI connections. Plus I had a device at the time that I wanted to use that could not send the audio to optical if you were using HDMI for video, so that pushed me to get the Denon once Woot had it available.

[DarrellS]

New audio and video compression is just another method of digital rights management. The harder they make it for the average user to encode and play audio and video files the better it is for the A/V industry. It's the vicious cycle of making the consumer buy special equipment to play the new file types.

The Denon replaced a completely useful and functional Pioneer receiver that lacked HDMI inputs.

Yeah, HDMI forced me to replace a very good (probably better than the one I replaced it with) Sony Receiver. All my other equipment was Sony or I probably would've bought something else. Maybe not. As much as I hate Sony's control over the Audio/Video industry, I've never had a problem with their equipment. I've never had to replace a component because it broke down. I just replaced them because they got outdated.

[ndjamena]

I had a Pioneer VSX-519V with HDMI, then I bought a slim-line VSX-S500 for my PC. Unfortunately it didn't seem to like my GPU or Monitor configuration and more often than not refused to initiate a connection when I turned them on. I found a VSX-S300 on clearance and bought it to see if it had the same problem. It didn't. So I connected the VSX-S500 to my TV... Audio Return... CEC Volume Control... I am NOT regretting that. (And that was just a step between HDMI 1.3 and 1.4)

[yoda313]

I do find it funny that my question wasn't really answered.......

But I appreciate the suggestion for hdmi amps.

However they do have hdmi to optical adapters. I actually picked up one that has rca audio out for my chromecast. It's hooked up to an old widescreen tv that I got that has scratchy speakers. So I have the chromecast connected to the adapter and the audio split out to a set of speakers with rca in. Then the hdmi passthroughs to the tv but I can do the audio separately. I could do 5.1 if i wanted but I don't have an amp with that tv, just the basic speakers with rca input.

pic:

[ndjamena]

Since it compresses better than AC3 I don't see how feeding it into a legacy AC3 decoder and getting legible sound from it would be possible. Variable frame sizes rules out an AC3 core...

[yoda313]

Since it compresses better than AC3 I don't see how feeding it into a legacy AC3 decoder and getting legible sound from it would be possible. Variable frame sizes rules out an AC3 core...

That's not good.

Any magic bullet to make it talk to legacy ac3 amps? Would they have preprogrammed it to work with ac3?

[ndjamena]

No one gives a crap about SPDIF anymore, if you're clinging to outdated equipment then, really, you're the problem, and no one is obliged to cater to that.

Any magic bullet to make it talk to legacy ac3 amps? Would they have preprogrammed it to work with ac3?

There's a magical, high-tech device called an RCA cable that will solve all your compatibility worries. Failing that there's always stereo PCM, or re-encoding to AC3. The possibilities are endless...

[2Bdecided]

Basically it seems to me to be a solution in search of a problem.

How is reducing the bitrate while maintaining the quality "a solution in search of a problem"?! Broadcasters are always trying to fit more channels into the same space. Haven't you heard of HEVC?

I bet they'll be a "transcode to AC-3" option for those who need it. We already have that on most UK Freeview HD STBs to get our HE-AAC and DD+ broadcasts into older equipment.

Cheers,
David.

[yoda313]

DD+ broadcasts

I thought dd+ was already ac3 compatible? I can do that with vudu dd+ on my legacy sd amp via fiber optic.

HE-AAC

That would be nice. That retains 5.1 then?

[ndjamena]

A Dolby Digital Plus service consists of one or more substreams. There are three types of substreams:
1: Independent substreams, which can contain a single 5.1 program. Up to eight independent substreams may be present in a Dolby Digital Plus stream. The channels present in an independent substream are the traditional 5.1 channels: Left (L), Right (R), Center (C), Left Surround (Ls), and Right Surround (Rs) channels, as well as a Low Frequency Effects (Lfe) channel.
2: Legacy substreams, which contain a single 5.1 program, and which correspond directly to Dolby Digital content. At most a single legacy substream may be present in a DD+ stream.
3: Dependent substreams, which contain additional channels beyond the traditional 5.1 channels. As dependent substreams have the same structure as independent substreams, each dependent substream may contain up to five full-bandwidth channels and one low-frequency channel; however these channels may be assigned to different speaker placements. Metadata in the substream describes the purpose of each included channel.

It has the equivalent of an AC3 core, but that won't get you access to the other sub-streams. In fact it's basically AC3 encapsulated by a better codec, much like all the other better codecs that retain legacy compatibility.

And you'll note, AC3 is also called Dolby Digital and DD+ means Dolby Digital Plus. If you scroll down the wikipedia article, you'll see DD+ is also called E-AC3. AC4 is something else entirely.

Typing AC4 into google gets you masses of posts about Assassins Creed 4, but if you add the dash, apparently the folks at Doom9 aren't any more enlightened than us, plus there's a rather disheartening description of the state of Australian Digital TV Everything else just points to the same page as pixar's first post.

[2Bdecided]

You need to improve your Googling Audio Compression AC-4 finds...

http://www.etsi.org/deliver/etsi_ts/103100_103199/103190/01.01.01_60/ts_103190v010101p.pdf

Unfortunately beyond the summary/introduction (which covers the same as the press release) it's pretty impenetrable.

Cheers,
David.