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Noise when changing channels

Discussion in 'TiVo Series3 HDTV DVRs' started by web1b, Dec 16, 2008.

  1. web1b

    web1b Member

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    Oct 2, 2006
    I replaced a 2 year old HTIB that started making a "feedback" noise whenever I watched an analog source using the digital optical audio.

    I bought a new Samsung HT=WZ412 and now that problem is solved, but there is a new audio problem. Now when I change channels, there is a weird ZAPPING noise that sounds like a Tazer. I went to the store and replaced the receiver and the problem remains.

    This is the setup:

    Tivo HD hooked up to an OTA antenna and output the video to my Panasonic 42" plasma monitor via HDMI (there is no audio on the display because it is just a monitor).
    For audio I have the digital optical audio output on the Tivo HD hooked up to Samsung HTIB.


    This is what it looks and sounds like:

    http://www.vimeo.com/2549121


    Does anyone have any idea what the problem is or is this receiver just incompatible with the Tivi HD.
     
  2. rvmeush

    rvmeush New Member

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    Dec 24, 2001
    Columbia, MD
    I have started to get weird audio pops and glitches when I do a 30 sec skip. I am also using a Samsung set with HDMI connection to Tivo. The skip had been working fine but just started to mess up tonight. This started happening after the Tivo did a reboot in the middle of changing screens on Tivo. I did another restart to see if this would correct the sound problem, but it didn't help.
     
  3. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    If you are using HDMI to your TV, be sure to set Settings -> Audio to PCM Output. Most TVs do not support Dolby Digital 5.1 through HDMI and may produce pops or screeching sounds in response to a 5.1 signal.
     
  4. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    Is the zapping sound coming from your TV or the HTIB?

    Is the volume on your TV muted?
     
  5. web1b

    web1b Member

    102
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    Oct 2, 2006
    The TV is just a monitor. It does not have sound or speakers. All the sound is coming from the HTIB.
    I'm using the HDMI cable only as a video input to the monitor.
     
  6. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    Sound receivers (especially cheaper ones) have trouble handling the breaks in the audio signal that result whenever you fast forward, rewind, 30s skip, replay, or change channels using the current TiVo software. Some receivers respond to these breaks with a high-pitched noise. Others lose audio temporarily for 2-4 seconds. And still others lose sound entirely until the next trickplay function.

    From reports on this forum, the TiVo didn't always cause these problems for these receivers. Some believe that TiVo used to mute the audio during trickplay functions, rather than breaking the audio signal -- they use this to explain the fact that their receiver did not exhibit these problems with the older TiVo software. Regardless, it is clear now that a) there are breaks in the TiVo audio signal during trickplay (FF, REW, etc) and channel changes, and b) this cause problems for some percentage of HITBs and A/V receivers.

    I own Denon and Panasonic A/V receivers and neither has a problem with the TiVo audio output. Both acquire and output audio [near] instantly after trickplay, and there is never a loss of audio, nor is there ever any noise other than what is coming from the program.
     
  7. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    To the above, you might try disabling TiVo sounds, if you have not already. I think one person mentioned that disabling TiVo sounds eliminated the problem for them. But this clearly is not a solution for all.
     
  8. web1b

    web1b Member

    102
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    Oct 2, 2006
    I tried changing the setting and it fixed the noise.
     
  9. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    That is not really a solution for a HTIB.

    When you change the audio output to PCM, you lose Dolby Digital 5.1 audio on HD channels. That's fine if you are using TV speakers, but not so good if you have a 5.1 surround speaker system.
     
  10. web1b

    web1b Member

    102
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    Oct 2, 2006

    Won't I still get 5.1 sound to the HTIB through the optical digital audio cable?
    I'm just using the HDMI for video to the monitor. I can't plug the HDMI into the HTIB because it doesn't have an HDMI input.
    I could swap cables and connect the Tivo to the monitor via component video and then connect the HTIB to the monitor via HDMI instead, but I don't see what that would accomplish.
     
  11. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    I can't recall whether Settings -> Audio -> PCM affects optical output, or only HDMI.

    If your HTIB indicates DD5.1 on HD channels, then I suppose you are fine.
     
  12. web1b

    web1b Member

    102
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    Oct 2, 2006
    I don't think I have 5.1 surround with the new settings, so I don't think this is a good fix and I don't know what else to try.

    I tried changing the cables so that the HTIB uses the HDMI cable and the Tivo uses the component video cables and when I turn Dolby Digital back on, the static noises returned.

    Does anyone have any other suggestions? It doesn't make sense that you can't use a HTIB with a Dolby Digital audio from a Tivo without these audio problems.
     
  13. web1b

    web1b Member

    102
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    Oct 2, 2006
    I tried turning the Tivo sounds off and it doesn't help.
    Muting would have been much better than hearing annoying static noises when changing channels, pausing and FF.
     
  14. kucharsk

    kucharsk New Member

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    Feb 2, 2007
    To be fair that's not really a digital audio receiver issue per se.

    There are two philosophies - one that all data should be output, and one that a certain number of good packets need to be seen to output sound.

    The latter approach quiets bursts of noise, but also means that you may have delays in audio being output after changing channels.

    There are also two approaches in audio output - one abruptly stops the digital data on pause or channel change, and one explicity sends a muted audio stream when valid received audio is not present. TiVos apparently do the former.

    This same issue is seen when connecting Pioneer DVD players to the same devices as they also abruptly stop sending data rather than send a data stream of no audio.
     
  15. M3 Adjuster

    M3 Adjuster New Member

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    Feb 11, 2009
    Dallas, TX
    I have this issue.. I bought a Tivo HD last week... I am using a Lexicon MC-1 preamp, which runs into an Adcom 5 channel amp for surround and a Velodyne sub. All of the components are connected to a Panamax power conditioner, and both cable and off the air antenna connections run through the conditioner and then into the Tivo. Clearly not a budget receiver setup. I switched from analog inputs to the optical audio out last night. The sound is FAR better, much more dynamic, especially on the low end with the sub. My daughter noticed that there is a popping when changing channels and sometimes when forwarding/rewinding. It primarily comes from the right front speaker. It quickly became VERY annoying. I went into the preamp menu and changed the audio to analog and the noise when changing channels went away.

    The Lexicon has the ability to look for the digital input in several ways.

    Automatic (searches and detects input..PCM, AC-3 Dolby Digital, or DTS)
    PCM only
    AC-3
    DTS

    With the setting on Automatic on the Lexicon, and Dolby Digital on the Tivo, the noise occurs. I can see that the preamp is struggling with decoding 5.1 vs 2.0 on certain channels as well and flips back and forth for 2-3 seconds and then it eventually locks in on 2.0.

    I switched to the PCM setting for the digital input on the preamp, and the noise is not there, when using the PCM output from the Tivo. Unfortunately, the sound is also very thin and uninvolving.

    With the setting on AC-3 (Dolby Digital) and the Dolby Digital output selected on the Tivo, there is not any noise. I recorded a Wyclef Jean concert from HD Net and it sounds terrific! For the most part, the HD channels are in 5.1. Lots of television channels however only come up in 2.0 and not 5.1 however... which is not optimal, and a few channels have NO output. I can't quite sort out why some channels come up with 2.0..


    No channels are encoded in DTS of course, although I imagine it would behave the same as AC-3 Dolby Digital.

    I tried turning off the Tivo sounds, and this does not make a difference. Bkdtv.. I think you are definitely correct in that the Tivo is not muting it's output with the current software. Indeed, it seems that the audio signal is garbled or varying, which causes an issue with many preamps/receivers.
     
  16. tmckay

    tmckay New Member

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    Oct 7, 2009
    I also had this problem - screeching and zapping sounds coming from the TV when I changed channels. I have a 37" LG LH40 directly hooked up to TiVo HD. I went into the audio settings and changed Dolby Digital to PCM and the sounds disappeared (thanks to advice I received here). I don't have a surround sound system so the I don't think I'm missing much with the audio - the audio from the TV is good by itself. I thought it might be a faulty HDMI cable, but I have a Monster 900 series and it's one of the better cables available.

    If I get an optical audio cord will that enhance the sound quality, or is it not worth the $$ not having a sound system?
     
  17. jjcool

    jjcool New Member

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    Sep 24, 2009
    Noticed this the other night on the parents setup. They have the Tivo HD hooked up to the tv with an HDMI cable and hear a noise when they change channels. I will try your solution tonight.

    UPDATE: Tried the fix, and it did indeed fix the problem. Now if someone can answer the question below, that would be fantastic.
     
  18. jjcool

    jjcool New Member

    38
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    Sep 24, 2009
    Mmmmm, monster cable.

    This begs the question, what happens if I add a surround sound receiver inteh future? The current setup is the Tivo HD going to the LG LCD TV via HDMI, and audio going through the tv speakers. Switching the audio settings to PCM right now is fine, but what happens when I add a receiver to the setup? Can I leave the HDMI to the tv alone, and get an optical cable and run that to the receiver to get the digital audio?
     
  19. 13rian

    13rian New Member

    1
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    Oct 13, 2009
    I'm having the same problem here. HDMI going to my 46" LCD and audio going to a Panasonic PT960.

    I hear audio pops when I change the channel and when I FF/RW. The screen also goes black temporarily sometimes, then comes back 2-4 seconds later. This has become very annoying. I have tried a new Tivo box (HD Series 3), new cables, and 2 different TV's. I haven't tried PCM yet since I do have surround sound, but will as a test.

    Any thoughts?
     
  20. bkdtv

    bkdtv New Member

    7,902
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    Jan 9, 2003
    DC Metro Area
    I assume you have HDMI going from TiVo to the LCD and optical going from TiVo to the Panasonic?

    Do that and make sure your TiVo is set to fixed 1080i output.
     

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