Surrond Sound working with ATT Cable

Discussion in 'Archived Threads 2001-2004' started by Ted D Grimm, Jan 9, 2002.

  1. Ted D Grimm

    Ted D Grimm Auditioning

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    I recently purchased a Yamaha Home Theater System which has 5.1 sound. I have ATT Cable which I run through my stereo. The 5.1 sound will work on Showtime, The Movie Channel, and all the digital stations. I can't get it to work on my Analog stations (2 through 66). I know that MTV, VH1 and Football games are in surround sound. Does any one have any suggestions?
    Thank You[​IMG]
     
  2. Ergin Guney

    Ergin Guney Agent

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    You may be confused about some terminology details and technicalities.
    You say that "5.1 sound" works on Showtime, The Movie Channel, and all digital channels. If, by this, you mean that your receiver receives and decodes a 5.1-channel digital soundtrack for these channels, I can image that Showtime and The Movie Channel can make at least some of their broadcasts in Dolby Digital 5.1 format, but it's not possible for all of your digital channels to be broadcasting 5.1-channel digital audio. That's not happening yet. Not even close! (I wish it were.)
    What you're most likely doing is seeing the "Dolby Digital" decoding indicator coming on when you are watching digital channels. However, what you are probably missing is that "Dolby Digital" does not automatically mean "5.1 channels". Dolby Digital is the name of an encoding format that supports a number of channel combinations ranging from a single mono channel (I believe it's called "Dolby Digital 1.0") all the way up to 5.1-channel "Dolby Digital 5.1". If your receiver is showing its "Dolby Digital" indicator, it could be decoding any of these formats; they are all "Dolby Digital". So what you are seeing in "all the other digital channels" is probably just stereo audio encoded in Dolby Digital, which is "Dolby Digital 2.0". Although you seem to imply by saying "5.1 sound works" that your receiver specifically says it's 5.1 channels, I have to assume that what it's really showing is a "Dolby Digital decoding" indicator or light, which does not directly imply anything about the actual number of discrete channels being decoded.
    As for the failure to get "5.1 sound" to work on your analog channels, Dolby Digital is, as the name suggests, digital. In order for any channel to have Dolby Digital 5.1 sound, at least the audio of the channel has to be transmitted digitally. That is not the case for analog channels, of course. So, while we've already ruled out true Dolby Digital 5.1 even for most of the digital channels, the analog channels cannot even have Dolby Digital 2.0 because of this.
    The answer to your question lies in another possible confusion about the meaning of "surround". The term "surround audio" does not imply the Dolby Digital format specifically, and more importantly, it not does not even imply digital audio necessarily (although Dolby Digital 5.1 is a form of digital surround audio, naturally). Surround audio goes back way before Dolby Digital. The most popular analog surround format is Dolby Surround and dates back to the 1980s. This is done by a form of processing that encodes four channels of audio (left, center, right, and a mono surround/rear channel) into two regular analog audio tracks in a way that the Dolby-Surround-encoded stereo audio track sounds like a perfectly normal stereo (two-channel only) track when played back on stereo-only equipment, but can be decoded into four channels and played back in a surround sound system when decoded by a Dolby Pro Logic decoder.
    What "MTV, VH1, and football games" (as well as most other major TV programming and even many commercials) have had since at least the mid 1990s is this type of analog Dolby Surround sound. In order to hear it as multichannel audio, you'll have to connect the analog stereo output of your cable box to your receiver and select Dolby Pro Logic decoding. (Consult its manual if you're not sure how that can be done.) Since you mention "5.1 sound", I'm assuming your receiver is capable of Dolby Digital decoding, and all such receivers available today always have Dolby Pro Logic decoding capability too for analog sources.
    I hope this clarifies at least some of the confusion. [​IMG]
     
  3. Jim_Stu

    Jim_Stu Stunt Coordinator

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    DPL & DPLII ??

    I was experiencing an annoying problem while viewing

    analog cable programs: The sound content, except for The History

    Channel and Monday Night Football would come from the

    main speakers only, but most commercials would be surround.

    I assumed this was due to the lack of a DPLII decoder in my

    Yamaha HTR-5280. Therefore, I view cable TV using the 'all

    channel' DSP and the problem is solved.

    JRS
     
  4. Ergin Guney

    Ergin Guney Agent

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    Jim,

    I'm a little suprised that most sound content came only from the main speakers. Do you include the center speaker in the definition of the "main" speakers? If not, it's really odd that the sound would come primarily out of the left and right channels, but not the center or the surrounds. But then, the sound for some channels on my cable service can be so screwed up that it can come out of phase or lop-sided for hours on certain channels.

    But if you do mean to include the center channel when you say the "main speakers", then it makes sense. When stereo soundtracks are recorded without explicit Dolby Surround encoding, you typically don't get very much content in the rear speakers when you decode them using Dolby Pro Logic. While, theoretically, DPL decoding can be expected to generate fairly good surround sound even from regular stereo soundtracks (i.e., not explicitly Dolby Surround encoded), in practice, unless it is an exceptionally good and "naturally miked" recording, most examples of regular stereo recordings don't result in very much rear channel content. This is because most stereo recordings are heavily modified in the studio (or, in many cases, the stereo separation added completely artificially in the studio) and do not contain good ambient sound cues. Therefore, decoding a regular stereo soundtrack using Dolby Pro Logic will usually result in most sound gathered into the three front channels, or in cases where the recording has little difference between the two channels, mostly into the center channel alone. (Mono recordings, of course, result in all sound coming from the center only, when decoded using DPL.)

    The reason commercials seem to have more obvious surround content might be because some of them are explicitly Dolby Surround encoded and also possibly because they are exaggerating the content of the rear channels for effect. Since they are trying to sell you something, it makes sense for them to try to wow you and impress you. Meanwhile, even good Dolby Surround encoded soundtracks will actually not have too much rear channel content, because surround channels are only supposed to carry the ambient sound and the environmental sound position cues (other than the occasional sound event that's supposed to sound like it happened behind the listener).

    Using Dolby Pro Logic II would probably help in the case of decoding regular stereo soundtracks (not explicitly Dolby Surround encoded) into surround sound. I'm not an expert on DPL II by any means, but I believe that is in fact the main point that sets it apart from regular DPL. (Well, that and the fact that the rear channels are stereo too in DPL II...)

    As for using something such as an "all channels" DSP mode, it will probably put lots of content in your rear speakers and make the sound come from all around you. If that's what pleases you then it means it does the job. But the soundstage it generates is probably a long way off from being the true representation of the sound ambience of the recording that you're listening. It must be moving a lot of front channel content to the rears in order to produce so much sound from them. In addition, (I don't mean to sound patronizing, but) keep in mind that the purpose of surround sound is not necessarily to make sound come from all around you. It is to make the soundstage more complete by filling in the "rear audio cues" that are otherwise missing (the room echos, the environmental noises, the additional depth for diffuse sounds, etc.). The vast majority of the sound should still come from in front of you, because that is where the image you're watching is, and where all the events that you see take place.
     
  5. Jim_Stu

    Jim_Stu Stunt Coordinator

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    Ergin,

    You have explained it well! I forgot to mention the center

    channel is fine I only noticed the difference on the surrounds. Of course I use DD or DTS for DVDs. I haven't

    pin-pointed the difference yet, but for some reason The

    History Channel sounds better than all others most of the

    time. ??

    JRS
     
  6. Selden Ball

    Selden Ball Second Unit

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    Jim,

    Many of the digital cable channels really are originating simple stereo (DD 2.0) most of the time. Actually, most of them are only transmitting monaural sound: the same audio signal is in both left and right channels. Their program producers can't afford the equipment and staff needed for real surround sound.

    Advertisers can afford it. They know you'll notice it.

    I don't watch the History channel much, so I can't comment on how it sounds here. However, some of the programs on the SciFi channel have very effective surround sound, especially the newer ones. Many older ones don't.
     
  7. Ted D Grimm

    Ted D Grimm Auditioning

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    Yesterday I was watching Titanic on VCR tape and the sorround was working. When I stopped the tape (the VCR was still on), the surround worked on all stations that broadcasted in surround. I had the VCR selected on my receiver also. When I slected TV on my receiver it quit broadcasting in surround. I want to thank everyone for there replies.

    Ted
     
  8. Rob Lutter

    Rob Lutter Producer

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    Titanic! On VHS!

    < faints >
     

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