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Feature Request. Dynamic range limiting

Discussion in 'DIRECTV HD DVR/Receiver Discussion' started by rahlquist, Aug 25, 2008.

  1. rahlquist

    rahlquist Hall Of Fame

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    I know this is a big request, and not one likely to get serious attention however.....

    I was watching 'The Sentinel' tonight on ch 513. I ran accross the #1 enemy of night owls like myself The dunamic range of the audio track on this presentation was very broad. In order to hear regualr voice tracks I had to have the volume up high enough that when the 'mood music' kicks in its horribly loud. I would love a way to suppress this range. I know its a tall order but for me it has always been one of my biggest gripes about TV.
     
  2. kayzersoze

    kayzersoze Cool Member

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    I know my reciever has a way of doing this, and I think a number of tv manufacturers include it as a feature. I would like it if the volume were not wildly different for hd channels vs sd channels(or commercials), but I don't think it is something we will see from the sat or cable companies themselves.
     
  3. Jeremy W

    Jeremy W Hall Of Fame

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    TVs and audio receivers can do it because they are actually processing the audio. Your DirecTV receiver is not doing any audio processing, it's either passing on the digital audio stream or converting it to analog stereo and outputting it. The receivers simply do not have the capability to do dynamic range compression.
     
  4. TomCat

    TomCat Broadcast Engineer

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    Anything that uses AC-3 audio encoding, which would be all Dolby 5.1, all ATSC OTA, and all DVB-S HD sat channels, has metadata parameters dynrang and compr that can be used to compress the levels directly at the STB. This means that the full dynamic range is preserved while level control can be made available on an ad-hoc basis to individual users, regardless of the other manipulation by broadcasters, which in the case of digital broadcasting, is not really done much at all (compared to all NTSC broadcasts which were compressed heavily).

    One of the reasons that audio levels seem to vary more on HD channels (and why they seem lower in level than their SD counterparts) is because the hooks to manipulating the audio are fewer and harder to get hold of by the broadcasters. They can't simply add compression and limiting as they do for analog signals, and they also don't have to, because digital audio has wide dynamic range and there is also no longer the problem of overdriving the audio transmitter (since there isn't one and the one that is there responds only to a digital input) which was something NTSC had to keep a tight reign on. Their control of dynamic range is actually limited to these metadata parameters, and very few of them even know that they exist, let alone how to change them. Luckilly, the networks take care of much of that for the broadcasters, but this also aggravates the "loud commercial" problem. Using the metadata parameters locally at the STB seems to solve that problem as well.

    My JVC digital AVR refers to this feature as "midnight mode", and it works very well to reduce dynamic range. It used to be that the difference in level between the CSI lab rats talking amongst themselves was too hard to hear while the re-enactments that illustrated what they were talking about would knock me right out of the La-Z-boy. I was constantly fiddling with the volume to keep up. Since I discovered "midnight mode" and set it to "2", I then set the volume to "27" one single time, and it has been there ever since. Problem completely solved. I'm not even sure where the AVR remote is, I use it so infrequently. This feature alone is worth the price of the AVR, which also has lipsync adjustment up to 100 ms.

    So the capability is there, right in the program streams. But I doubt either would ever be a feature on a low-end DVR like the HR2x. It should be, however.
     
  5. Jeremy W

    Jeremy W Hall Of Fame

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    I never said it was impossible, I was saying that DirecTV's receivers don't have the capability to do it.
     
  6. rahlquist

    rahlquist Hall Of Fame

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    hey I aint above replacing this 10 year old RCA AVR, what model is that JVC?
     
  7. evan_s

    evan_s Hall Of Fame

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    My hk340 has a night mode that even has different levels that does that. I'd imagine any relatively recent model that handles DD decoding would do that since it's part of the DD spec.
     
  8. cygnusloop

    cygnusloop Hall Of Fame

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    My Onkyo TX-SR605 has a "Latenight" mode with Off/Low/High settings. I use it all the time after the wife and kids have gone to bed. Works great. While I would like to listen to everything at high volume, with full dynamic range, alas, life is compromise.... ;)

    As TomCat said, not only does it squelch the nasty loud commercials when I don't get to the >>> button quick enough, it makes the low dialog understandable while taking the edge off the loud explosion/gunshot type stuff.
     
  9. texasbrit

    texasbrit Well-Known Member

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    I am not sure why you think this should be a feature of a DVR. Surely it would mean that the DVR had to decode the digital bit stream and then re-encode it again. That's an expensive feature to add when it really should not be in the DVR at all. Using the metadata and dynamic range limitation are features that you would expect to be at the A/V receiver or TV, somewhere that already has a decoder and is creating the five channels of audio. The DVR should just do what it is doing now, pass the digital bitstream without modification and let the A/V receiver do the rest.
     
  10. Stuart Sweet

    Stuart Sweet The Shadow Knows!

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    I would like a capability like this but I don't think it should necessarily be in the DVR.
     
  11. t_h

    t_h Icon

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    I think there needs to be some consideration that a lot of people plug the dvr right into their tv set without an avr.

    I know..."How GAUCHE!".

    We have a bunch of tv's, and while I have an AVR somewhere its just more complexity than I can manage and besides, the three year old loves buttons and knobs.

    So its either in the tv or in the DVR for us. None of our tv's support any sort of dynamic range compression and the volume differences between dialog and music drive us nuts.
     
  12. paulman182

    paulman182 Hall Of Fame

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    I am not using my AVR right now but at least one of my TVs has dynamic range compression.

    I will never use it.
     
  13. rahlquist

    rahlquist Hall Of Fame

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    The reason I suggested that this be part of the DVR is that not everyone is going to have a AVR to plug into, something D* recognizes by putting plain RCA jacks on the unit and giving the option to disable Dolby. Since the DVR is the one converting the Digital sat sig to analog audio out the dynamic range adjustment can easily occur in the dvr.
     
  14. TomCat

    TomCat Broadcast Engineer

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    I don't think I implied either that you said it was impossible or that current DVRs do have the capability. Actually, I agreed with everything you said, and was just adding more information. Kinda how forums work.
     
  15. TomCat

    TomCat Broadcast Engineer

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    JVC makes a lot of models. Mine is 2 years old, so there are probably newer ones out there, but I can't say enough good about my D-701, which has seven 105w amps in it. There was also a D-401/402 which had a little less power per channel, but was still an excellent bargain at about $275 street price (mine was about $330, I think about 850 list). That's pretty good for an amp with quality and features rivaling anything else under about a grand (street price). About the only feature it doesn't have is output connections for a second set of main speakers. It was also about the only "digital" amp that has HDMI upconversion and HDMI switching that could be had for less than about $800-900 (street) when it came out.

    Although JVC made good audio amps in the 80's, since they dropped out for a number of years I was a little skeptical that something they made today could hold its own with better-considered brands, but it really does. I would have to say its in the class of mid-to-top-level Yamahas and Denons, and probably better than anything I've ever seen from your Onkyos, Pioneers, Kenwoods, etc. You'd have to go up to a Rotel or something like that to beat it.

    The term "digital" is actually a misnomer. It is actually Class-G, which is a form of pulse-width modulation (to be truly digital it would have to process as pulse code modulation). But the benefit is efficiency (and how green that makes it). Audio is converted to PWM for processing, and then low-pass filtered back to 20 kHz, which completely and transparently removes the high-frequency (so high it was inaudible anway) distortion created by conversion to PWM.

    But the amp is so efficient that it fits in 2RU without heat sinks yet it still incorporates seven 105wrms amps and probably weighs only about 25 lbs. Do that Class-B or C and you are talking about an amp that weighs 70 lbs and is 5RU high (and can heat a room all by itself). The fact that all this power masquerades as any other component in size even though it has the power of a monster analog AVR means it has a great "wife factor" as well, thanks to the "digital" (PWM) processing and how efficient that is. Highly recommended, and the price can't be beat.
     
  16. CCarncross

    CCarncross Hall Of Fame

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    It should reside in your tv or your AVR if you have one, NOT in the dvr box. It should not reside in the STB ever......if you really want to get picky, the pressure needs to be on every tv station to provide uniform audio. We as consumers have to apply the pressure on the broadcasters, NOT the programming providers.
     
  17. TomCat

    TomCat Broadcast Engineer

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    I'm not sure where you got the idea that I think it should be a feature of the DVR. I'm perfectly happy having that capability in the AVR. I only said that it was very possible to do technically in the DVR, even though I am not convinced that it's a good idea or cost-effective or practical. I'm also not sure why you think that would imply a decode/re-encode. "Surely", it would not.

    Even if done in the DVR I'm afraid it would not really change how things are done very much, and would not in any way imply a re-encode. Metadata or no metadata, everything stays encoded and digitized until playback from the HDD, so nothing there would change. The metadata is only available during AC-3 decoding, but that is a normal counterpart to decoding the MPEG-2 or MPEG-4 video, all of which normally happens soon after being read from the HDD anyway. Decoded audio and video is either then ported to an HDMI transmitter chip and sent to a display and/or AVR in that protocol, or the video is converted in a local DAC and sent out as analog component and the audio is sent either as optical digital or also converted to baseband analog and sent out to the AVR or to the display's audio inputs.

    While I'm sure you are not among these folks, there are a lot of folks out there that have a fuzzy idea of how things work and are unexplainably convinced somehow that decoding and converting to analog are the same thing. Of course they are not the same at all, they are quite separate serial processes. Decoding ALWAYS happens in the DVR, while conversion to analog, which also ALWAYS happens even if some time later, may happen there, or in the display.

    Bottom line, audio and video, as well as any accompanying AC-3 metadata, would still be decoded once and only once at the exact same point it always is. Any manipulation that this might imply to dynamic range would be done right then and there, and the audio which now would have a modified dynamic range could then either be carried on to the AVR or display as digital, or as baseband analog just as it normally is, even if it might make a bit more practical sense to do that in the AVR. But there is no technical reason NOT to do it in the DVR, and so it is not in any way out of the realm of possibility to one day see that as a feature of a DVR.
     
  18. hasan

    hasan Well-Known Member

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    If for some strange reason it was implemented in the sat box, I want it defaulted to off, and made switchable (of course). I didn't spend a small fortune trying to increase the dynamic range out of my system, to only have it ruined by some post processing in my DVR.

    My HT system (Onkyo) has an "evening" mode to suppress the dynamic range. I've never used it.

    The issue of levels runs a deep gamut, some of it station based, some provider based (commercials), who knows how much is sat based.

    Every DD 5.x station (and DVD for that matter), is well below the level of 2 channel stereo at my house. It's always been that way, some local stations are much worse than others. (one is -13 dB compared to the others!)

    There is no easy solution to the loudness issue.
     
  19. spartanstew

    spartanstew Dry as a bone DBSTalk Club

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    We just hit the "watch TV" button on our Harmony remote. It's not that complex.

    Oh, we also have a 3 years old, but he never touches the AV equipment. And even if he did, I'm not sure why that would hinder the use of our AVR. I'm assuming my TV has speakers that work, but don't know for sure as I've never used them.
     
  20. TomCat

    TomCat Broadcast Engineer

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    I understand that sentiment, but realize that the intelligence to do this IS INDEED provided by every broadcaster already. The dynrang and compr metadata parameters are added features that are automatically already provided by all HD broadcasts. This why it was designed and is exactly HOW THEY SOLVED THE PROBLEM of uneven audio. If you have the capability of manipulating these parameters in your AVR or display, well then you already know that. If you don't have that capability, well then you're probably still pissed because you think the problem still exists.

    The fact that the ability to manipulate the dynamic range is also built into every STB automatically (and there is some capability in every ATSC STB out there, whether the consumer is allowed to have the hooks to adjust it or not, as a part of the AC-3 standard) does not imply that the onus is on someone other than the broadcaster. The onus IS INDEED on the broadcaster, and this is their response to the problem. The fact that broadcasters have characteristically NOT responded in the past is not because they didn't recognize or want to fix the problem, it is because up until now it has been nearly impossible to do. The AC-3 system solves a lot of that problem much better than it ever could be addressed in the past, and is characteristic of other changes the industry will be making that will eventually solve this problem completely.

    Until that time, buying an AVR with this particular capability is a very good idea for evening out the volume changes that are still there. For the first time we have the option of doing something to take advantage of technolgy that fixes the problem rather than simply moaning about our fate and everyone else's inability to fix it. Of course if you still WANT to moan about it, DON'T take advantage of the technology, DON't buy gear that can help fix the problem, and go on and keep on moaning on into the night as much as you want.

    The fact that the actual manipulation happens in the STB does not imply that it is the consumer's responsibility, it is simply a part of being able to preserve the dynamic range and noise level for situations that call for normal dynamic range while also providing an option for more control over dynamic range should the consumer want to avail themselves of it. IOW, if the dynamic range were adjusted at the source, then no consumer has a choice over whether they get full dynamic range or compressed dynamic range, and the noise floor is artificially raised, compromising quality. This is what was at the root of an inability to fix the problem when all we had was analog.

    Keeping the intelligence to do this under the control of the broadcaster while the actual manipulation happens automatically and transparently to the consumer in the STB, is the best of both worlds, especially if you have the capability to take advantage of the metadata, which is an option if you also happen to have the right gear.

    Actually, IMHO, since the fix is already there in the broadcasts, maybe the onus is no longer on the broadcasters at all, and should really be on the equipment providers. It would cost little if anything to provide this capability for allowing the consumer to control dynamic range in this manner on each and every STB out there, including DVRs. Unfortunately, 90% of what we buy does not provide consumer controls for this, does not provide them access to a fix for this problem that is already right there in every HD broadcast.
     

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