Channel Issues & Questions

Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
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mc510
Level 7

Which codecs are passed-through by Roku Media Player?

On my Roku 2XS, Roku Media Player works fine with MKV having AAC stereo audio, but I get silence if the audio is AAC5.1, AC3, or DTS (consistent with https://sdkdocs.roku.com/display/sdkdoc/Audio+and+Video+Support). Question is Does the Roku pass-through everything that it can't decode, or only DTS? Because if it passes AAC5.1 and AC3 to my TV, I would expect the TV to be able to decode them since they are part of the official ATSC digital broadcast specification. 
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10 Replies
renojim
Level 10

Re: Which codecs are passed-through by Roku Media Player?

Make sure your Roku 2 XS audio settings are not set to "Stereo". I wondered why my mother's Roku 2 XS had the same problem and when I switched from "Stereo" (I believe to "Auto", but can't remember for sure) she started getting the 5.1 AC-3 tracks to play. There's "Audio mode" and "HDMI" settings and I can't remember if I changed both or one or the other, but before I made the change she only got AAC stereo tracks and silence if the video had AC-3 tracks. I don't have any media with AAC5.1, so I can't speak to that.

-JT
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atc98092
Level 16

Re: Which codecs are passed-through by Roku Media Player?

This support page lists all the supported codecs. Note that your media has to be in a supported container, as well as the codec itself. Also, AAC isn't supported via passthrough at all. Stereo AAC is converted to PCM. 5.1 AAC is decoded to 2.0 PCM only on certain Roku TVs and players, specifically the 4640 Ultra. Again, check the support page for complete info.
Dan
Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
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mc510
Level 7

Re: Which codecs are passed-through by Roku Media Player?

@renojim, I have played around with all of those audio settings and can’t get AAC5.1 or AC3 to play. Still not sure if it is throwing the audio away, or passing it through to the TV and the tv is failing to decode.

@dan, thanks for that link. I think it clarified that AAC is never passed through, like you said. Stereo AAC is decoded; I guess it is throwing away AAC 5.1? Pretty much everything else is “some rokus” or “many rokus”. I think it’s saying that the roku will either decode ac3 or pass through, but I’d really like to know which it’s doing.

[EDIT] The "?/Help" screen in Roku Media Player lists the supported codecs; presumably this list is customized to the actual capabilities of each model? For me, it lists AAC but not AC3, and then it further states that Dolby Digital is passed through from MKV, MP4, and MOV files. So I guess that answers my question about the Roku. Still leaves the question of why my tv isn't able to decode AC3 (the audio standard for broadcast digital tv) over HDMI.....
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atc98092
Level 16

Re: Which codecs are passed-through by Roku Media Player?

"mc510" wrote:

[EDIT] The "?/Help" screen in Roku Media Player lists the supported codecs; presumably this list is customized to the actual capabilities of each model? For me, it lists AAC but not AC3, and then it further states that Dolby Digital is passed through from MKV, MP4, and MOV files. So I guess that answers my question about the Roku. Still leaves the question of why my tv isn't able to decode AC3 (the audio standard for broadcast digital tv) over HDMI.....

Yes, that help screen does display different info based on the Roku model. On my Ultra, it shows H.262 supported, while my Stick does not. I can't say why your TV doesn't decode the AC3. I've had no problems with my Stick when playing DD tracks. I play my media via a DLNA server that has profiles that detect the media's codecs and transcode if necessary. Since I wrote the profiles, I'm pretty sure what they do. Smiley Happy  Since my Ultra is connected to an AVR, the profiles don't touch Dolby Digital or DTS tracks. Since my Ultra can't bitstream any HD audio, those have to be transcoded. And since H.262 video support was added to my Ultra not too long ago, I can now leave that video alone as well. 
Dan
Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
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RokuDale
Level 8

Re: Which codecs are passed-through by Roku Media Player?

The Roku2XS doesn't support AAC5.1 decode. That is why you get silence with that audio track.
What is your settings for digital audio? It usually should be left at Auto, and the Audio Mode should also be Auto.
When digital audio is set to Auto, it should tell you what audio codecs the TV is telling the Roku that it can decode.
rokudale
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mc510
Level 7

Re: Which codecs are passed-through by Roku Media Player?

"RokuDale" wrote:
What is your settings for digital audio? It usually should be left at Auto, and the Audio Mode should also be Auto.
When digital audio is set to Auto, it should tell you what audio codecs the TV is telling the Roku that it can decode.
rokudale

I've tried lots of different combinations of audio settings, right now it's at Audio Mode="Auto (Stereo)" and HDMI="auto detect"
"?/Help" menu in Roku Media Player says that AAC, MP3, WMA, WAV(PCM), AIFF, FLAC, and OGG are supported. Is that where it will show what codecs the TV is telling the Roku that it can decode? Surprising that a HDTV that can play AC3 from broadcast wouldn't be able to play AC3 over HDMI, but there you are.
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Miami_Son
Level 8

Re: Which codecs are passed-through by Roku Media Player?

I would say the Roku doesn't "passthrough" anything, rather there are some codecs it will transcode and some it will just ignore. If it could actually passthrough audio then we wouldn't have the issues with HD audio that we currently have and it would make our lives so much simpler and enjoyment so much better.
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atc98092
Level 16

Re: Which codecs are passed-through by Roku Media Player?

It does passthrough audio, but for whatever reason Roku doesn't support lossless audio bitstreaming, although it is now reported that the 4660/61 Ultra will passthrough DTS Master Audio. My Ultra is a 4640, so can't confirm. While Roku has never publicly acknowledged the reason, speculation is licensing fees to Dolby and DTS. You would think that allowing a bitstream passthrough wouldn't require a license, but I can't confirm that as a fact. 
.
But Roku does bitstream (passthrough) both Dolby Digital and DTS lossy tracks via optical or HDMI to a downstream AVR. Ignoring the audio I would call passing through  Smiley Wink
Dan
Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.
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RokuDale
Level 8

Re: Which codecs are passed-through by Roku Media Player?

Auto(Stereo)/Auto means it didn't detect that the TV/AVR can accept Dolby or DTS. (It presumes all AVRs and TVs can accept PCM Stereo).
However some AVRs and TVs don't tell us what it can handle so therefor there are the non-Auto manual settings.
Some TVs can handle DD even though they don't tell us so select DD and see if it works. But there is no guarantee since Roku is trusting that you know what you are doing when you take it off Auto.
Some earlier TVs won't decode DD but will pass it through their optical port to an AVR that might be connected and let it deal with it.
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