Center channel missing from some streamed videos

[Beebes]

Not sure I’m a beginner or an audiophyte, but I’m posting here because I found a similar question posted in this forum.

I usually stream video from a Roku Ultra 4800R, with surround sound processed by a Yamaha RX-A3050 A/V receiver. I’m normally happy with the surround sound the receiver delivers to my 5.0.0 speakers.

I noticed recently that when I play the current NBC series The Endgame from the Hulu app on my Roku, the center channel is silent, making dialog difficult to understand.

I suspect the problem is caused by NBC or Hulu, but I’m not sure I can rule out my own setup. Can someone tell me whether the following behavior eliminates my setup as the source of the problem?:

The receiver Information menu shows the Endgame source audio format as Dolby Digital+ 7.1 (3/4/0.1) -- i.e., 3 front channels, 4 surround channels, and 1 LFE channel. It shows output to 5.0.0 (which correctly corresponds to my 5.0.0 speaker setup). As noted above, I hear no center channel audio.

Other Hulu videos, including the ABC series Gray’s Anatomy, have the exact same source audio format and speaker outputs, and they have clearly audible center channels.

In this comparison, the only variable is the TV series being played. Am I correct to conclude there’s nothing I can do on my end to fix the problem? If it’s useful, I can post additional details about my Roku and receiver audio settings.

Out of curiosity, I tested Endgame playback using other apps and devices, with the following results:

Using the same Roku and receiver, but switching to the YouTube TV app: Receiver shows the same audio source/output formats as when I use Hulu. Center channel is not audible. This suggests the problem is not Hulu-specific and might be caused by NBC, Roku, or my setup.

Using the same receiver, but switching to the Hulu app on Apple TV 4K: Receiver shows source audio format as PCM 2.0 (2/0/---) and output as 5.0.0. Center channel audio sounds good.

Using the same receiver, but switching to an OTA HD TiVo, with signal coming from my local Los Angeles NBC station via a rooftop antenna: Receiver shows audio source format is Dolby Digital 5.1 (3/2/0.1) and output is 5.0.0. Center channel audio sounds good.

Thanks for any insight you can provide.

 

[Teetertotter?]

My opinion, it is the source that is transmitting to Hulu?

 

[j_garcia]

Streamed content can be hit or miss, regardless of what format it says is available for a particular app or content, and I would expect it is the stream and/or broadcast that has the issue based on your description. There may be something you can do, similar to how most TVs and streamers work, you can set the Roku to "force" Dolby or DTS instead of the native bitstream. It effectively re-encodes it and plays back only in that format, with whatever channels were present.

 

[Trebdp83]

Hello and welcome to the forums. Some content is available OTA in DD 5.1 and even in DDEX in some cases. Then, depending on the streaming service and device, might only be available in 2.0. The Roku makes things even messier depending on its settings. Based on the information posted above, I think you need to change a couple of settings in the Roku. When the Digital output in the Roku is set to Auto, it will output a Dolby Atmos signal and trigger the info on the receiver to show DD+/Atmos or DD+. Since you are not using surround back or presence speakers, the Atmos metadata is not being processed by the receiver and it is displaying DD+. Now, this does not change the channel output of the content. 2.0 tracks are not converted but sent over in the 3/4/0.1 signal with only the front channels being active. So, two channel material will only be heard from the front channels even though it says Atmos and you will not be able to use processing of any kind to get audio to the center channel.

Roku settings are a mess and there are two places to select audio output. First, make sure the "Digital audio format" setting is set to "Passthrough", not "Auto." "Auto" activates the Fakemos output and locks out processing of 2.0 tracks. Then, in the "Streaming audio format" setting, make sure it is set at "Auto" so Dolby and DTS signals are passed accordingly. These settings should ensure the passthrough of the track signal to the receiver without any changes from the Roku on their way out. Then, with 2.0 tracks, you should be able to apply Dolby Surround processing to them to get audio to the center channel as you do with the Apple TV 4K. All audio will output as PCM with the Apple TV 4K. Atmos track metadata will not be indicated or processed without the use of surround back or presence speakers and these tracks will also display as PCM rather than PCM/Atmos. To check this out, simply assign surround back or presence speakers and Atmos tracks will display as Atmos/DD+ from the Roku and Atmos/PCM from the Apple TV 4K.

 

[Beebes]

Thanks to all of you for the replies and, especially, to Trebdp83 for your deep knowledge and detailed explanation. I followed your suggestion and changed my Roku digital output format from Auto to Passthrough, and that fixed the problem.

After fixing my Roku settings, and continuing to use my receiver’s Dolby Surround processing as usual, I confirmed your expectation that surround processing of the Roku stream works the same as I observed earlier with the stream from my Apple TV: I hear center-channel audio, and my receiver shows the source audio format as PCM 2.0 (2/0/---). I also compared, by ear, the sound of the Roku PCM stream to the sound of the same video played on my TiVo, which my receiver tells me is in Dolby Digital 5.1 (3/2/0.1) format. As far as I can tell, they sound the same, and I get sound from all 5 of my speakers.

If I ever upgrade to a Dolby Atmos system, I might be back for more help.

 

[Trebdp83]

Joy! Glad it worked out. I forgot to mention that these settings apply to a Roku Ultra. The Roku Streaming Stick+ has a slightly different set of Audio settings. Applying Dolby Surround to 2.0 tracks will result in practically the same perceived audio output as OTA DD 5.1 tracks in a 5.0 system. Many shows I’ve watched on my TiVo broadcast in 5.1 while streamed versions have 2.0 tracks depending on the service app and device used for playback.