I am not a video expert. I used to be an audio engineer (like a 1000 years ago) and have done some video editing on my own professional grade editor for giggles but not in the last 10 years.

And yet, I am seeing something that makes me curious. So I thought I would finally ask.

I get cable over OTT via a Roku. Periodically, on channels that have minor packet loss, I have noticed that ads will lose any actor voice and the voice over portion of the content. The background and other sounds are there. Just the voices are missing. For example, an ad for a popular insurance company will have all the background sounds, however, the voice of the person in the video and the voice over announcer are gone. This does not happen for shows. It also does this for most any ad periodically and inconsistently. The same insurance ad can show again in the next ad block just fine. One ad can be missing voices, the next ad is fine, then the third ad is missing the voice. This can happen on any channel from time to time and seems to be tied to very minor packet loss. Basically, the channel is working just fine, just very minor periodic packet loss. This may be a hint.

Strange huh? Any ideas? It is not really a problem for me, just a curiosity. In fact, it is kind of nice so I am not really complaining.

  • Is the audio feed multichannel? – Gyan Aug 27 '16 at 6:07
  • @Mulvya I have no idea. It is a live stream of one of any cable channels via ACC (I assume is the stream protocol) on Roku. Be that as it may, I am sure they are getting this via a satellite as it exists for a market. I am not sure if they are inserting local ads like traditional cable would. It seems that all the ads are national except for the broadcast channels (also streamed) which does not seem to have this problem now that I think about it. – closetnoc Aug 27 '16 at 6:14
  • @Mulvya BTW- When I say I am not a video expert, I mean I do not know my arse from a podcast. ;-) After school, I started my career as a systems internals engineer (computer) and quickly forgot everything useful. Worse yet, I am retired and a landlord, farmer, antiques dealer. So now I only which end of the shotgun goes where. Cheers!! – closetnoc Aug 27 '16 at 6:18
  • That definitely sounds like a bad downmix, but I don't know why that would happen intermittently. – Michael Liebman Aug 27 '16 at 23:33
  • @MichaelLiebman I like the missing center channel idea. It aligns with the facts fairly well. I tried and set the Roku to Stereo versus Auto (there are only two options) just to see. It still happens. Again, this is not a general streaming problem, so I am thinking that it is coming from the cable provider that way and not happening on my end. At least now I am. I ask because it seemed so odd to my old school mind. ;-) – closetnoc Aug 27 '16 at 23:50

I don't have a definitive answer, but what you're describing sounds like phase inversion on one of the stereo channels. This causes cancellation when heard in mono of anything centered in the mix, as an announcer voice would most likely be. Someone listening in stereo would not hear much if any difference, so I assume you're listening to a mono feed. It's hard to imagine a scenario where a commercial is delivered in a way that would separate the main channels but leave the background sound.

Why only sometimes? Speculating again, there may be one misconfigured server in a group of servers, and playout of any given spot is randomly coming from that server. It's also likely that these are local insertions, since an issue like this would probably be detected quickly at a national level.

  • Thanks Jim for the reply! I think you are onto something. It could be the center channel. As for the ads being local, I think they are all national. This is not the traditional cable set-up and there does not seem to be any local ads other than on the broadcast channels. I do listen through my Aragon 2ch set-up and there is phasing and depth when I use it streaming films, however, I cannot say that I have checked this on a cable channel for a long time. I will check out if there is a difference I can see between off the back of the Roku or through the T.V. Curious. Cheers!! – closetnoc Aug 27 '16 at 16:52

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