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AAC 5.1 Down to Stereo vs. 7.1 Transcode


majorsl

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I have my first Roku, coming from Kodi.  My feelings are mixed. 

 

The problem I'm having is that my content with 5.1 AAC is only being played as stereo via Digital when Emby Direct plays it.  This seems to be a thing according to this thread:

 

https://forums.roku.com/viewtopic.php?t=95522

 

"Roku4 can decode multichannel AAC. It will downmix to stereo pcm and play that."

 

I have some content that is 7.1 AAC which forces Emby to decode it, likely because the Roku is advertising it CAN play 5.1 AAC but not 7.1.  The 7.1 gets transcoded and comes through in glorious sounding 5.1 surround.

 

The question is: how do I get Emby to transcode everything so I'm not losing channels thanks to Roku's limitations?

 

The last comment in that thread seems to indicate the the Plex folks even went so far as forcing an AC3 encode to certain Roku models at one point.

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Jdiesel

Would be nice to have the option to force transcoding to ac3. I can't recall if BlueNeon has the ability but maybe check it out, if it doesn't @@speechles might be able to force that behavior. 

Edited by Jdiesel
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Happy2Play

Would be nice to have the option to force transcoding to ac3. I can't recall if BlueNeon has the ability but maybe check it out, if it doesn't @@speechles might be able to force that behavior.

 

Yep there is a option in preferences in BNN.

Edited by Happy2Play
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Do you know what is it called? I see Default Audio which I set to AC3, but that doesn't seem to do it. Emby still reports that it is direct playing.

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You can already do this using the blue neon roku app. @@Jdiesel is indeed correct. :)

 

https://emby.media/community/index.php?/topic/24151-theme-blue-neon-night/

 

Open preferences from the options row. Then find the preference for "default audio" and change this to ac3. Do the same for "unknown audio" change it to ac3. Then "force surround" change to yes. You cannot let the app use auto-detection as it will direct play and we dont want that. To get your desired effect choose "force transcoding" from the "more..." button on the items detail screen before you press play. Doing this will change the aac 5.1 into ac3 5.1. This will (copy) the video stream and convert the audio stream. You can confirm this by pressing OK on your remote as the video plays. It will show onscreen how the item is being transcoded. The issue you have is indeed roku downsampling aac 5.1 to 2.0 over hdmi.

 

Also to make a better experience with less transcoding, raise max refframes to 16, raise max framerate to 61, and set your maximum video bitrates appropriately for local, remote, and livetv. The rest of the preferences are up to you. If you need any of the options in the app explained let me know.

 

Sent from my Nexus 7 using Tapatalk

Edited by speechles
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Thanks for the quick response folks! That's why I love Emby, someone always helping out!

 

Well, my first experience with Roku is definitely a disappointment.  Back to Kodi with the Emby plugin I go.  I was hoping to go with the Roku as a cheaper/easier to maintain solution than my Linux Kodi installs, but this is definitely more work in the long run.  I might try an Amazon Fire with Emby for better luck.

 

If I don't eBay the Roku, I'll probably move it to one of the Kid's TVs that is only stereo anyway so down-sampling won't be an issue.

 

I'll keep an eye on this thread in case the Roku Beta Emby App changes the behavior. IMHO, if Roku is falsely advertising it's capabilities and down-sampling AAC 5.1 to 2.0, maybe Emby should force a transcode or have the option like the Plex folks did.  It's a situation where it's Roku's fault for sure, I know. :(

 

Again, thanks for the kind and quick responses.

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Jdiesel

Yeah it is unfortunate that the Roku doesn't convert multi-channel AAC to multi-channel PCM. I don't have much multi-channel AAC content so it doesn't bother me too much but if I had a lot I would probably ditch the Roku too. 

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@@majorsl the only emby roku app that can force play methods is blue neon. The official app only allows auto-detection. Thats why on blue neon, the preferences you change (default audio, etc) affect transcoding. There is no way to affect direct play since the roku is handling it all itself. Thats why you have to "force transcode" and change those preferences. The official emby app needs to use this same mechanism. In the "more..." menu place options to "force direct", "force transcode", or "use auto-detection". Also need to have a setting so transcoded audio can be forced to use surround (aka ac3).

 

ad8164be80a9dfd4ce5d1acd197a8777.jpg

 

@@ebr are you reading this? What are your thoughts? @@Luke any opinion? In light of rokus firmware debacles not having the option hurts emby. Food for thought?

 

Sent from my Nexus 7 using Tapatalk

Edited by speechles
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@@speechles I mostly understood what's happening and appreciate the explanation with a little more detail that filled in gaps for me.  I'd love to have options you mentioned in the official app too, I fully understand this is Roku and not Emby and I would hope others do too!

 

I look at this, and a possible settings option, as "Roku completely dropped the ball and Emby made it right."

 

I'd be more than willing to dedicate my time to testing any such options. I'm a systems admin by trade and live and die by logging myself, so know how to provide them when asked!

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So if I understand, you when a video has 7ch aac you want to forego direct play so that the audio can be converted to ac3?

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@@Luke

 

You misunderstand. The apps already do this for 7.1 and downsample to 5.1 just fine. The issue is the roku advertises its deviceinfo support as AAC with 6 channel. The app then realizes the device can direct play AAC in 5.1 and direct plays it.

 

The issue is the roku is downsampling directly on the device and passing AAC 2.0 through the hdmi instead of 5.1 So it is more the roku is lying in its device info the app gets.

 

To correct this the app needs to have capabilities changed so AAC at most only supports 2 channel. This would let auto-detection keep surround. But at the same time, it isnt direct playing for those with stereo setups then when it could be.

 

Its a problem with roku devices themselves and one which may give the impression that emby is at fault. Do you see the problem? It is a complex issue when the device lies, how would you handle this? Ive handled it by having a force transcode option and various audio preferences that control which codecs get used when transcoding. This approach requires user intervention of course which isnt optimal. It is a complex problem with no easy solution.

Edited by speechles
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it would have to require a setting, with the default being off. it's just asking for complication. really the right thing to do is report to roku and get the fix there, but we understand sometimes that can take a while.

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@@Luke

 

Quote below from this url

 

 

 

Support for AAC (Advanced Audio Coding)

 

Roku devices do not support AAC pass-through. Instead, Stereo AAC is transcoded to PCM stereo.

 

Roku TVs and some Roku players decode 5.1 AAC to PCM stereo for headphone, internal speaker, and HDMI/ S/PDIF (optical) output. However, Roku devices that support Dolby Audio decode connected via HDMI or S/PDIF (optical) to an A/V receiver that also supports Dolby Audio, will convert the audio to Dolby Digital 5.1.

 

So the part that appears broken, is it isn't automatically detecting dolby (ac3) and converting AAC 5.1 to AC3 5.1 on the device like it should be. It is now only converting AAC 5.1 to AAC 2.0 and passing that along the hdmi. I can confirm that prior to firmware 7.6 this all worked correctly. So what needs to happen is roku will hopefully correct this, and make what their own documentation says should happen, happens.

 

There isn't anything you need to do per se, since the ball is clearly in rokus court. But the longer they linger on a fix, the more a setting would be required. Time will tell. Tick tock tick tock.. xD

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If you look in the original post I made to the forum discussion over at Roku, they seem to be well aware of it.  In fact, documentation indicates "that's the way it is."  The discussion seems to indicate that they don't want to pay for a license for AAC 5.1 and are cheaping out and down-sampling to stereo.

 

Plex "fixed" it by doing what we're discussing here: forcing a conversion of AAC 5.1 to AC3 when a Roku device requests streaming because the Roku is lying as to what it is doing with the audio.

 

I have no confidence that Roku will fix it on their end, but this is also clearly my only and last Roku device.

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they don't want to pay for a license for AAC 5.1 and are cheaping out and down-sampling to stereo.

 

Actually, that isn't really a fair assertion.  The consumer is the one "cheaping out" :).  People want cheaper and cheaper devices so something has to be cut somewhere or companies cannot exist in order to bring you these devices.

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Actually, that isn't really a fair assertion.  The consumer is the one "cheaping out" :).  People want cheaper and cheaper devices so something has to be cut somewhere or companies cannot exist in order to bring you these devices.

Then it would be fair to say if your device is not capable of a certain audio format, don't advertise it to add-ons.  The device should only advertise AAC 2.0 and let Emby transcode to DD/AC3.  That would cost Roku nothing but a firmware update with a change possibly rolled in "next time".  As it stands, it cost them already several more units purchased from me and who knows how many more that stumble on this thread and the one over there.  Not that they'll care of course unless even more people vote with their currency!  :D

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Then it would be fair to say if your device is not capable of a certain audio format, don't advertise it to add-ons. 

 

I understand that feeling from our perspective (believe me, I agree that would be better for us).  However, from their perspective that would be a bad move because it would mean they would not work at all with any streaming sources delivering that type of audio (the source would have to be able to convert it).

 

They aren't selling these boxes to you and me.  They are selling them to people who are consuming streaming data from online services so their ability to accept a multitude of inputs and still output audio (albeit inferior audio to you and me) is much better for them than refusing to accept it at all.

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I'm just going to use it with a TV with stereo only and forget it.  I'm probably going to go in the Android TV direction for the main viewing areas in the house, be it a nVida Shield or Fire TV (if Amazon ever releases the new version and they are back in stock).  Hopefully those behave better.

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The issue is the roku is _supposed_ to decode AAC on the device.. It will report it can decode AAC not pass-through. There is no lie here. The roku used to say it would pass-through, now it says it decodes on device. No lies in the device info.

 

The lie comes in when the documentation says:

1) AAC 5.1 will be converted to PCM stereo for headphone, internal speaker, and HDMI/ S/PDIF (optical) output

2) However, Roku devices that support Dolby Audio decode connected via HDMI or S/PDIF (optical) to an A/V receiver that also supports Dolby Audio, will convert the audio to Dolby Digital 5.1.

 

Now clearly #1 is happening. AAC 5.1 and 7.1 are used by netflix, amazon, and vudu. You can see why these are decoded on the device rather than pass-through. It eliminates issues people have with no sound.

 

But, #2 is no longer happening. if the roku device supports it (roku 4, premier, premier+, and ultra) and your hdmi or spdif is connected to a sink device that supports dolby, the AAC 5.1 will be converted to AC3 5.1. This is decoded on the device not passed through. It is this behavior that is presently broken on the roku.

 

So the short of it is, the app has to work around the short coming, or users will only get the benefit of stereo. It has nothing to do with licensing, or roku is cheap. It has to do with how complicated their firmware must be. Imagine all the different firmwares, and having to merge code into them all. Must be a major headache. I suspect the 7.7 firmware was a redo of 7.6 using cleaner code with more comments and such. To make future revisions easier and faster. So eventually we will get there as they add back 7.6 things to the 7.7 core. It will just take time. How long? Who knows.. thats why I gave the ominous tick tock tick tock above. If it takes a long time, people will assume emby cannot do what plex can, which is transcode aac 5.1 to ac3 via change of capabilities and blocking aac 5.1 from ever being decoded by a roku. If roku fixes this issue quick, users wont have time to blame emby. But the longer the issue remains, a fix by emby is required.

Edited by speechles
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So eventually we will get there as they add back 7.6 things to the 7.7 core. It will just take time. How long? Who knows.. thats why I gave the ominous tick tock tick tock above. If it takes a long time, people will assume emby cannot do what plex can, which is transcode aac 5.1 to ac3 via change of capabilities and blocking aac 5.1 from ever being decoded by a roku. If roku fixes this issue quick, users wont have time to blame emby. But the longer the issue remains, a fix by emby is required.

I may be reading the above incorrectly, if so, my apologies. That seems to suggest 5.1 AAC worked in 7.6? My new Premiere came with 7.6 and most definitely did not work.  I declined the update given the 7.7 problem thread here.

 

From the thread I have referenced twice now, "rokudale" from Roku Engineering lays it out in their own forums:

 

 

 

1. No version of Roku firmware supports sending out multichannel PCM over hdmi, only PCM stereo is supported.

2. The Roku-3 and Roku-2 are unable to decode any multichannel AAC audio because the hardware doesn't support it.

3. The Roku-4 has hardware that can decode multichannel AAC, but (see #1)

4. The RokuTVs have a Dolby license that includes support for transcoding multichannel AAC into 5.1 Dolby. If you have an AVR attached to the ARC/SPDIF that can decode Dolby you will get multichannel output.

 

Also, there is a higher license fee for AAC 5.1 decode to PCM 5.1 vs decode to downmixed PCM stereo.

 

rokudale

 

It doesn't seem to me that Roku has any intention of fixing anything and specifically mentions a higher license fee. Now, I realize I'm just a dumb consumer, but that tells me if I read between the lines, they are trying to save a penny at least as a factor.

 

For giggles, even though I'm an Emby Premiere purchaser, I installed Plex and it does indeed automatically transcode 5.1 to ac3 when the Roku plays as a work around. And it sounds great.

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In firmware version 7.5.x it used to work. With the new 7.6 its introduced its own slew of problems. This is why 7.6 was ... scrapped so quickly. Now on your device there may not be an update yet. Roku does these off serial # batches. If your device is a rokuTV then roku has to partner with your TV manufacturer to work on updates.

 

I have a roku 3, roku 2XS and a roku ultra. I know for a fact when I got my roku ultra with 7.5 this did work. AAC 5.1 was decoded/encoded to Dolby Digital (DD) by the roku ultra on-the-fly. The files could direct play no issue. Now when direct playing all I ever see there is AAC.

 

To see this for yourself, use the blue neon app, and look on the right hand side of the OSD when playing an item. How the roku understands the audio will show there. If it can't understand the audio this will show NONE. Try using "force direct" on audio you know wont play, but has video that will. The video will play but you get no sound.

 

"Roku needs to do some esplaining to Lucy why her I love lucy episodes aren't dolby no mo!" .. say that in a Ricky Ricardo accent. Then make a cuban stare at roku like you are waiting for an answer. One may never come.. LOL

 

139ad00a1a2d35f6f8864c4f2c6b5c83.jpg

Edited by speechles
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