Dolby digital audio passthrough not working

[theRCRH]

Just saw this thread over on the kodi forums.
http://forum.kodi.tv/showthread.php?tid=289735
it saids fireOS is API22 and AC3 isn't working. That is consistent with my findings.
I guess I'll have to stick with SPMC until the next FireOS update is released.

Nah, they are wrong ac3/api22 using non-iec format (what audiotrack wants) works fine on my firetv2 and nvidia shield. There is something else going on. Maybe related to encoded bitrate.

Am I the only one reporting this problem on a first gen Firetv?
Isn't AC3 encoding pretty standard at 384? Please let me know if I can do any more testing. I've randomly tried dozens of files & all fail. What bitrate do you think could be the problem?
In a couple of hours I'll be able to test an ota live TV feed & I'll let you know if that plays.
edit: The live TV broadcast with AC3 audio also failed.

[davilla]

Somewhere in the man cave, I have a firetv1. Looks like I might need to find it. You would not believe the number of arm boxes stuffed away there. I really need to purge.

[theRCRH]

Somewhere in the man cave, I have a firetv1. Looks like I might need to find it. You would not believe the number of arm boxes stuffed away there. I really need to purge.

Alternatively you could start a museum. Does your town offer tourism grants?

[davilla]

/me points to his original KayPro II and Mac SE30.

[theRCRH]

/me points to his original KayPro II and Mac SE30.

I can't compete with those computers but I do have a popcorn hour a110 tank sitting next to me.

[amet]

ZX spectrum here -> https://en.wikipedia.org/wiki/ZX_Spectrum

[LoneSwan]

->Isn't AC3 encoding pretty standard at 384?

This is a common bitrate for PCM, which may be part of the problem. Your receiver, which is capable of decoding the AC3@384, could be switching to PCM mode, then cycling again (periodically, from your description). Always a problem when devices have no provision for a manual override of their auto settings _and_ "they" make the wrong choice.

Reading the Wiki on Dolby DD+: it appears there should be a legacy DD stream(core) _at 640_ as part of any DD+ audio encode. My guess is that some receivers can handle a different input, while others assume the stream is PCM which then kills the output. And, I assume Dolby is quite happy with the ongoing results which "encourage" replacement of all those devices which can't deal with "pass-through"... unless they pay Dolby for a fix, and the user buys something new.

Even with the manual audio output settings added to the Fire TV's, which worked great with my Fire v1 for about 8 months, sometime near the end of May an update put DD audio output back to NOT working. Since then, I have been watching for any posts that might tell me what is wrong with legacy DD and Fire TV's.

A post on another forum related the same experience, as here. The solution found was to use SPMC, choose 2 channel mode, this brings up option to choose "transcode", which results in working 5.1 channel audio. {I will have to find the original post to quote it in detail.}

I loaded MrMC a while ago, but am just now about to start using it, precisely because I have given up on Amazon solving the DD audio problem on their own: expecting them to break it again, repeatedly.

Walker {Virginia, USA}

[theRCRH]

->Isn't AC3 encoding pretty standard at 384?
A post on another forum related the same experience, as here. The solution found was to use SPMC, choose 2 channel mode, this brings up option to choose "transcode", which results in working 5.1 channel audio. {I will have to find the original post to quote it in detail.}

Walker {Virginia, USA}

Loneswan, another solution (as I posted above viewtopic.php?f=17&t=872#p5661) is to use SPMC and IEC passthrough. I hope that option gets introduced into MRMC soon.

[LoneSwan]

The question is what MrMC can do with a "Dolby" stream without a Dolby license? I don't see that Dolby is in any position to press this issue, due to a long history of problems with the Dolby Digital Plus audio format, but I have yet to see a comment posted by a program developer (such as VideoReDo) that states what they can and cannot do without Dolby's permission.

Below, I have cut & pasted excerpts from research concerning Dolby (Plus) and their association with Netflix:

{avsforum} 04-06-2014: Does anyone know what the bitrate (or bitrates) Netflix is using for Dolby Digital Plus?

{ " } 04-11-2014: It's 192 Kbps DD Plus. It was 384 Kbps, then Dolby declared that their new encoding tech was twice as efficient as before and Netflix halved their encoding rate.

{community.sony.com/t5/Home-Theater-Products/} Dolby Digital Plus incompatability - Netflix sound distortion STR DN1040
Sony Engineering is working on a firmware release to address the sound distortion due to low bit-rate streaming of Dolby Digital Plus. {2014}

{ " } 12-23-2014: I put the blame squarely on Neflix on this one. Netfix decided to switch to Dolby + and apparently did no testing to see what it worked with. 5.1 support was broken on the vast majority of streaming devices when they made the switch. Samsung, Sony, Apple, Amazon, Roku ,Chromecast, just to name a few. I cant beleive they made a wholesale change like that when the vast majrity of devices used did not support it.

{ " } ‎02-23-2015: There are no shortage of devices out there with problems with the Netflix implementation of DD+. Seems every mfgr has had to deal with this.

http://www.dolby.com/us/en/technologies ... -plus.html
Dolby Digital Plus is an audio technology based on Dolby Digital 5.1, the established standard for cinema...
If your system includes only Dolby Digital, you'll still get 5.1-channel surround sound, with the highest-quality Dolby Digital signal possible—Dolby Digital Plus content is easily converted to a traditional Dolby Digital signal.

http://www.dolby.com/us/en/technologies ... -sheet.pdf
Dolby Digital Plus ensures compatibility with the millions of Dolby Digital equipped receivers and home theater systems currently in use, with even better audio performance than standarddefinition DVD. Dolby Digital Plus soundtracks are easily converted to a 640 kbps Dolby Digital signal without decoding and reencoding, for output via S/PDIF. The 640 kbps bit rate, higher than the 448 kbps used on DVDs, is fully compatible with all existing Dolby Digital decoding products such as A/V receivers...

{avsforum} 06-14-2016: I chatted with Netflix support multiple times and got different answers. Nothing really helps. Seems like the only option that I have is upgrade my receiver.

{avsforum} 09-11-2016: So you guys are STILL seeing this DD+ distortion issue on new Denon products? Seriously? My original post was in 2013...wow.
I just now discovered this on my 2015 Denon 3200. This is frankly unacceptable as I watch a ton of Netflix. I wish I could return the receiver for another one. Not even stereo works with Netflix, constant auto dropping out no matter what settings. In the meantime I'll have to wait for a 4k HDR with Dolby vision streaming device to spend more money on when I shouldn't have to.

-{Now, compare the history referenced (_briefly_) above, with the current technology horizon: }-

https://www.cnet.com/news/dolby-vision- ... ormat-war/
April 14, 20166:10 AM PDT by David Katzmaier
[Excerpts]
If you snoozed through the past few generations of TV "innovations," you're not alone. 3D was a bust. The "advantages" of 4K are imperceptible even if you squint. Curved TV screens are pretty useless. And smart TV is great, but all those cool streaming services are just a Roku, Chromecast or Fire TV away...
...This is critical -- there's no way to add Dolby Vision to a TV via a software update. It requires Dolby's chip (or system on a chip), Dolby's certification process and, of course, its licensing fees.

Hanno Basse, Chief Technology Officer at 20th Century Fox, as well as President and Chairman of the Board of Directors at the UHD Alliance. {The Alliance is an industry group that created a certification for premium 4K TVs as well as content}: "We prefer open standards, and HDR10 utilizes open standards," he said. "Just like with software, you typically get much broader adoption with an open standard. We're mastering our content in that format, we like the results and our creatives like it. We frankly don't see the need to augment HDR10 with a proprietary solution at this point."

Netflix will serve both HDR10 and Dolby Vision content, so an owner of a non-Dolby Vision TV will be able to watch Netflix HDR. But the company has been more vocal so far in its support for Dolby Vision, and has been working with Dolby for longer to develop its HDR library. Netflix is now streaming Season 1 of "Marco Polo" in Dolby Vision, and will add "Daredevil" soon. [Netflix will offer both HDR formats and serve one or the other depending on which one your TV supports.]

Asked: Jim Freeman, Amazon VP of Digital Video, how Amazon will serve TVs that handle both. "We do testing of all devices to determine which is the best customer experience, and we'll optimize that experience for the customer." In other words, Amazon will determine, based on its own testing, whether a particular TV gets Dolby Vision or HDR10. Freeman also mentioned surveying customers for their preference between the two formats, and even the possibility of allowing a customer to choose one or the other, provided a TV can handle both.

With Dolby's power and industry clout, I'd be surprised if Dolby Vision goes away anytime soon.
---------------------------------------------

I don't know what agreements happened between Dolby and Netflix back in 2010, when Netflix announced its plan to adopt Dolby Digital Plus. I can only guess that Netflix had (and still has?) a significant reason to adamantly refuse to offer any option for surround sound other than Dolby Plus. I _do know_ that Netflix's position has caused and continues to create a great amount of frustration for some of their subscribers.

Walker

[davilla]

2016/2017 is a major turning point regarding DTS/AC3. The patents expire Note this is 5.1 flavors. The exact dates are hard to figure out. For passthrough, you do not need a license. All you are doing is transporting bytes. The decoder (ie, amp/receiver) carries the license. Both DD and DTS will never say this in public but you do not need a license to transport bytes.

Next another very interesting thing happened in 2016. Apple included support for native AC3/EAC3 decode for iOS9/tvOS devices. And if you look at fireOS specs, and AC3/EAC3 is listed as present for mediacodec decode API and transport (AudioTrack). No fanfare, just bang, it was there. You will see many devices starting to include both AC3 and DTS 5.1 support soon as very soon the patents go pop.

The issue under fireOS is the AudioTrack API for passing through AC3/EAC requires what they call raw or non-IEC wrapped encoded audio frames. Internally, in fireOS, they do the IEC wrapping for transport over HDMI. Sounds nice but it seems that some fireOS devices barf handling certain AC3 encoded bitrates. My thought is NetFlix/Prime is AC3 encoding a very specific way and this gets the gold seal of approval. But it is device specific. FireTV1 barfs, FireTV2 is fine. AC3 comes in several flavors, some are fine, others are not. Go figure To pass DD licensing, you have to pass their test suite of encoding. They do the test and get out their pass/fail stamp depending on how you handle the test files. Think on this for a bit

Now as people who have run SPMC have figured out. If you set SPMC to force IEC wrapping, AC3 passthrough works. What that means is instead of using the native AudioTrack API for AC3, you setup for two channel PCM, 48KHz and shove IEC wrapped frames down. As long as nothing 'touches' it, bytes are bytes and out it goes. If a mixer touches it, bah, you get bad noises.

We handled all passthrough as IEC wrapped transported as two chan PCM in the initial version of MrMC for fireOS, and that's why it worked. Then we figured, hey, raw (non-IEC wrapped) is listed so why not use it... Buzz. And that is why it 1st worked then stopped working in a later version. We also handle DTS this way on fireOS as it DTS not listed under the supported AudioTrack encoding flavors. And we plan to return to IEC wrapped AC3 for those effected fireOS devices. We prefer to do it a smart way rather than using a settings hammer.

More Side note, I also have a 2015 Denon 3200. Denon totally messed up 5.1 AC3/DTS handling on the 2015 3200 and below models from day one. Mine would refused to switch... Feed it HD audio and it was fine. Grrrr. But that was until the DTS-X update that come out last month. Now it works like a champ and I've swapped out my older Denon 1912 for the 3200 and am a happy camper. I'm told that 3200 and below are made in a different place using a different chipset than those above the 3200 model. Go figure, and I passed on an open box 4200 when getting the 3200