losing center channel audio

Discussion in 'TiVo Roamio DVRs' started by Hubb1e, Oct 3, 2014.

  1. Oct 3, 2014 #1 of 34
    Hubb1e

    Hubb1e New Member

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    So my Tivo is dropping the audio on the center channel sometimes. The dialog goes mute and all I get is the audio from the side and rear speakers which on some shows like kid's shows means that there is little audio except the music. It will happen in the middle of the show, not just at the start of the show.

    I can fix the issue for awhile by going into the settings/audio menu and clicking up and down a few times until the tivo beep noise comes back. At first I thought I needed to change the audio to PCM and back to DD, but I found all I need to do is to just click up and down in the menu and the audio comes back. The audio is then fixed and I can watch my show again for awhile. This makes me think it is something wrong with the way the Tivo beep noise has been programmed.

    I'm pretty confident that the issue is not with my audio reciever as it doesn't have this problem on any other source, and I can fix it from within the Tivo itself.

    I noticed this after the last update a few days ago. Anyone else see something like this? Tivo chat support hadn't heard of it.
     
  2. Oct 3, 2014 #2 of 34
    NorthAlabama

    NorthAlabama tabasco rules

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    i have experienced this twice, both times during awards shows, and only with singing performances - vocals would drop from the center channel a fraction of a second into the vocals, and would return when the singing stopped.

    i chalked it up to faulty production equipment settings or bad live surround mixing by the technician for both shows, and switched the audio on my avr to multi-channel stereo.
     
  3. Oct 3, 2014 #3 of 34
    Hubb1e

    Hubb1e New Member

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    Multi channel stereo on the AVR doesn't work because it drops the whole audio channel before processing, so you might be able to hear a little more, but the majority of the dialog is mapped to the center channel so I'll notice the dialog gets very very faint even in stereo mode. It's happening in the Tivo processing and not in the AVR.
     
  4. Oct 3, 2014 #4 of 34
    NorthAlabama

    NorthAlabama tabasco rules

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    you're right, switching the avr is not a solution, simply a workaround to level the sound, and prevent alternating loud blasts of vocals followed by faint trickles. i never imagined it was a tivo issue since it's happened so rarely for me.
     
  5. Oct 4, 2014 #5 of 34
    Hubb1e

    Hubb1e New Member

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    An update for anyone who sees this problem:

    So I was able to get around the issue of no dialog by switching the Tivo to output PCM audio vs Dolby. It's only 2 channel, but at least it works for now. I haven't had the problem come back with PCM.

    I was also able to fiddle with the Tivo while it had lost the center channel. When I'm missing the center channel audio, I can make the center channel audio come back whenever I enter an OLD standard def Tivo menu. Once you enter the menu and click around a few times, the Tivo beep comes back and my audio is fixed for a few minutes. So this issue is with how Tivo has implemented the DD audio output and is probably a bug having to do with muxing the Tivo beeps under DD audio.
     
  6. Oct 4, 2014 #6 of 34
    XIBM

    XIBM Member

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    What audio output are you using? - HDMI - optical etc,
     
  7. Oct 4, 2014 #7 of 34
    Hubb1e

    Hubb1e New Member

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    Hdmi

    Update 2: PCM didn't fix it. It worked for awhile and then broke again. I'm switching to Optical. Thanks for the idea.
     
  8. NorthAlabama

    NorthAlabama tabasco rules

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    i've experienced the issue with both hdmi and optical, specifically the lead vocal track. it happens intermittently, and only with songs (not spoken dialog).

    normally lead vocals can be heard through the center speaker when using dolby surround. now, on certain songs, the lead vocals are missing from the center channel, and only resonant lead vocals can be heard on the remaining l & r channels.

    this is affecting existing recordings, and can be resolved by switching my tivo or my avr to pcm audio only (no dolby).
     
  9. JohnS-MI

    JohnS-MI Active Member

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    Are you sure you have ruled out AVR? I am having a similar issue, but I think I have narrowed it down to my AVR. Basically my TV optical out and my Roku (fed into an optical takeout box) do it too. I can solve it by changing the AVR to another optical input for a moment, then switching back.

    In the case of the Tivo, I can pause, back up and correctly play the recorded passage after I have "tweaked" the AVR. That tells me the error is not in the Tivo recording.
     
  10. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    You can transfer the show to a PC and see if it's in the source or not.
     
  11. NorthAlabama

    NorthAlabama tabasco rules

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    how, when i have only 1 avr? no other audio is effected (blu-ray, audio cd, pc or online streaming), and pandora works great.

    i've tried different hdmi cables, optical vs hdmi, and multiple decoder settings on the avr. it isn't happening on every existing recording, only a few. i've noticed it a couple of times on "live" awards shows (above).
     
  12. nooneuknow

    nooneuknow Well-Known Dismembered Member (Lurk Mode On)

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    Just to chime in a few notes:

    I have two Sony Bravia TVs, one with Sony apps, right before "smart TVs", and one with nothing of the sort. Both support 5.1 input via HDMI. I use analog outputs to drive a set of stereo speakers w/subwoofer, as poor man's rear surround channel. There are no AVR/receivers in use here.

    A few TiVo updates back, the dialog seemed "underwater", so I had to switch both to PCM, via the base Roamios. This is the first time I have had to use PCM, and don't like that I had to turn off all TiVo sound effects, to not get a deluge of them doing trickplay.

    The simulated surround (for TV internal speakers) for both TVs had worked well before. Now with or without it, PCM is the only way I don't lose dialog (or have that "underwater" effect on it).

    I'm still getting the losses/dropouts between full-screen and menus, but not between guide and full-screen. TiVo now rewinds the programming to make up for what was lost, often overlapping with what wasn't lost. I don't get the bailing wire & duct tape nature of this...

    Just some data, in case it helps...
     
  13. NorthAlabama

    NorthAlabama tabasco rules

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    i think i've eliminated the source for my issue, the songs in my saved recordings played ok just a few months ago.
    others have mentioned center channel dialog issues recently, too, but i'd forgotten...thanks.
     
  14. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    AC3 is a compressed audio format so it's basically impossible for TiVo to do anything to the AC3 bitstream that would only effect the center channel. They would need to decode the stream, manipulate the PCM audio and then recode it to effect a single channel like that. And we know from the fact that they can't even insert their "bee-doop" sounds when playing an AC3 source that they're not doing that. I guess they could be corrupting the header in some way, but even that seems to be unlikely to cause an issue with a single channel. A corrupt header would most likely cause a complete decode failure which would result in silence on all channels or random noise. Unless maybe they're messing with the channel layout portion of the header. I guess that could cause the decoder to do weird things depending on how it's designed. But they'd have to be doing that intentionally as the header is a pretty random sequence of bits.

    This is almost certainly an AVR issue. I just can't think of anything else that could cause an issue with a single channel like that.
     
  15. NorthAlabama

    NorthAlabama tabasco rules

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    but only for songs, and never spoken dialog? and only certain songs in certain recordings? and only tivo, not blu-ray or other dd media devices?

    i'm not convinced it's my sony avr, not yet.
     
  16. nooneuknow

    nooneuknow Well-Known Dismembered Member (Lurk Mode On)

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    Plus I'm not using any AVRs, other than what is built into my Sony Bravia TVs.

    As it has been stated/debated in some threads, TiVo does not offer any method of a true "stereo" (L+R only) output option, even when PCM is selected. Essentially, my TVs have internal AVRs, which must take the DD or PCM supplied by my TiVos and convert it to stereo output.

    Every other device I can connect to my TVs offers the option to output stereo via HDMI. Yet, TiVo never has offered any options but DD or PCM, and TiVo Roamios (base models) are the only "problem childs", when it comes to audio issues, for me. Roamio has been the only device I have been forced to stop using DD over HDMI with.

    I wonder if there is something about Sony (and some Samsung) devices, being part of the equation as a whole, when it comes to the bigger picture. I also wonder if TiVo offered internal passing or downmixing of/to true stereo, via HDMI, to the processing/receiving device, if my dialog (typically a center-channel heavy target), would not suffer, as it has been throughout TiVo's adventures in tweaking the HDMI audio, trying to fix all the various issues it seems only TiVo fails to know how to output for maximum compatibility.

    This is all just speculation, based on years of observations, plus issues I never had with HDMI, until the Roamio, and the new issues TiVo seems to create for me with nearly every software update. Every now and then, they roll a version with minimal issues for me, but then bring them back, or add more, when the release notes say they fixed something, which was not broken for me...
     
  17. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    How could TiVo possibly know that it's playing a song and not spoken dialog? It's no smarter about that then your AVR.

    Maybe the audio is switching to 2ch in those broadcasts? AC3 has the ability to mix 2ch and 5.1ch in the same stream. It's common to see the stream drop to 2ch during the commercials. Maybe your AVR doesn't deal with the transition well. Or maybe TiVo is screwing with the headers and marking them all 5.1ch even when the stream drops to 2ch and that's what's causing the issue. That's the only thing I can think of that TiVo might be doing that could cause this sort of issue.

    If you transfer the show to a PC you can see if this is the case using VideoReDo. You can set the tumbnails to display 2ch and 5.1 as different colors and then look at the point where the center channel drops out see if it drops to 2ch.
     
  18. NorthAlabama

    NorthAlabama tabasco rules

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    i agree, and the same goes for my avr. i've now noticed it with spoken dialog on "today", only with live announcer voice-overs (sponsorships) during the segue from studio to outside plaza events (is losing sponsor announcements a feature or a fault?). after the segue, everything's fine.
    my avr reports changes to the audio stream mix on it's main display (2ch stereo, 2.0 dd, & 5.1 or 7.1 dd surround). each time it's happened my avr is reporting 5.1 dd surround (no mix changes). if i pause and resume, the display still reports 5.1 surround.

    it happens so rarely at this point, it's not really worth buying another avr or taking tivo to another avr to test. i posted primarily in response to the op, was curious to see if anyone else experienced the issue, and because it was a change from previous behavior.

    the recordings affected are also available on demand, using on demand as the source doesn't change the result. if it becomes more frequent, i'll start looking to testing options.
     
  19. pgoelz

    pgoelz Active Member

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    FWIW, just as a data point I have noticed that at transitions between program and commercial, the phase of the left and right channels will very occasionally change. It will suddenly sound like the phase of one of the channels reversed. Depending on program content and how the audio is being processed, this could kill the center speaker if I had one?

    Further, if I back up and play through the transition point, the next time it won't do it. That would seem to eliminate the program source, no?

    I'm using HDMI from the Tivo to my Samsung TV, then optical from the TV to the AV receiver. The receiver decodes to Dolby with four speakers.... front left, front right, rear left and rear right. No sub and no center speaker.

    Paul
     
  20. Dan203

    Dan203 Super Moderator Staff Member TCF Club

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    If TiVo was mucking with the headers then that's what you would see. I recommended transferring to a PC because that gives you the raw stream so you can see if it ever drops to 2ch.

    If it does and your AVR still reports 5.1ch then that's the issue. Either the TiVo is mucking with the headers or your AVR isn't detecting the change and it's trying to play 2ch as 5.1, which could explain the weird mixing.

    The standard for 2ch is L/R and the standard for 5.1 is L/R/C/LFE/SR/SL so if a 2ch was decoded as 5.1 the decoder might just fill the missing channels with silence which would produce the effect you're describing.
     

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