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AV Rant #284: Weird and Awesome

Listen after the final music for a spoiler-free review of the new Avengers movie (it is out in Australia so Tom went and saw it). Liz is out of town this week so Rob H. steps back in. Lots to discuss including a listener question about PCM, an article on Ars about Mastered for iTunes, and 4k/8k news. We have a Netflix news this week – CEO has been ranting and they’ve been affecting ratings. Tom and Rob debate the new Hobbit movie being shot and shown in 48fps. Rob thinks no, Tom thinks all the people that are whining about how it looks need to shut up. Rob has a warning about Windows 8. Star Trek: The Next Generation is getting an update for Blu-ray. Thanks for listening. Check out our new Facebook Page. To check our our YouTube channel where you can see the recordings of our show videos, click here. Download Tom’s FREE superhero-themed ebook Bob Moore: No Hero wherever ebooks are sold (or given away in this case). Visit Tom's website for download links as well as links for the two full-length followups -  Bob Moore: Desperate Times and Bob Moore: Hostile Territory. Friend Tom on Google+ to join in on one of our hangouts.

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  1. Mark
    May 3rd, 2012 at 13:54 | #1

    After listening to the podcast, I was wondering if you could expand on the “bass management” subject that cropped up in the discussion about encoding/decoding. Does the receiver/amp pass speaker/crossover configuration data back through hdmi to the blu-ray player DAC so that it could properly handle bass management? Is there more to “bass management” than main channel low frequency + LFE mixdown? Yeah, it’s a noob question. Great show as usual, and just in case you (Tom) haven’t had the chance to say “whatever”; Windows Media Center + a cablecard tuner is the absolute best DVR available, very slick, very pretty, and sometimes (wait for it) it actually works.
    thanks,
    MC

  2. Jeb Butler
    May 4th, 2012 at 13:19 | #2

    Howdy!

    509 has been putting out some clips shot on the RED Epic http://www.red.com/products/epic .
    Highlights are 5k resolution, 120 fps and 18 stops of dynamic range.

    Check it out a clip here here.

    http://www.youtube.com/watch?v=VWyXNYKE6r8&feature=player_embedded

    I won’t prime you all with what you should notice :)

    Jeb

  3. Rob H.
    May 5th, 2012 at 03:14 | #3

    @Mark

    Yes, the bass management and other processing of the sound signal can be a tricky subject and a bit tough to understand – mainly because different receivers have different capabilities depending on what sort of signal they are receiving.

    At its most basic, the receiver is fed some sort of audio signal – let’s just imagine a regular old Dolby Digital 5.1 signal to start with. The receiver will use its Dolby Digital decoder to turn the DD signal into PCM. Then the receiver can apply bass management, room correction, tone controls, or any other type of DSP. The final signal that results then gets passed through the receiver’s digital-to-analogue converters (DACs) and sent to the amplifier section where the now-analogue signal is amplified and sent to the speakers.

    Now let’s imagine that instead of a Dolby Digital 5.1 signal, the receiver gets fed a Dolby TrueHD or a DTS-HD Master Audio signal via HDMI. To start with, not every receiver has TrueHD and DTS-HD decoders built in, which would mean that such receivers cannot do anything with this signal. But assuming that your receiver DOES have TrueHD and DTS-HD decoders, those decoders go to work and turn the TrueHD or DTS-HD MA signal into PCM.

    Now here’s the thing: decoding TrueHD or DTS-HD takes a fair amount of processing power. And some receivers have fairly slow (by today’s standards) processors. My Onkyo TX-SR705 from several years back is one such example. It can decode the TrueHD or DTS-HD MA signal just fine, but it basically “runs out” of processing power and doesn’t have enough processing power “left over” to perform full bass management, room correction, etc. The manual for my TX-SR705 actually details in a chart how any TrueHD or DTS-HD signal has to be kept below a certain bit-rate and sampling frequency in order for things like bass management and room correction to be available with those formats. If I try to feed my 705 receiver a 96/24 TrueHD or DTS-HD signal, it will decode that signal into PCM and amplify it, but it will NOT perform bass management or Audyssey room correction or THX post processing. The decoding of the 96/24 TrueHD or DTS-HD format literally “uses up” too much processing power and the 705 “runs out of steam”!

    Now, in the case of my 705, if I feed it a 5.1 96/24 PCM audio signal via HDMI, everything is fine! Since the receiver doesn’t have to decode anything (the signal is already PCM – having been decoded inside the Blu-ray player or having been a PCM audio track to begin with), now it has enough processing power available to apply bass management and room correction and THX processing and what-have-you.

    The thing is, some receivers are programmed so that if a raw PCM signal comes in, they won’t touch it! They will just send it straight through to the amps. In these cases, it has nothing to do with processing power, it’s just a choice on the part of the manufacturer not to touch raw PCM signals.

    So really, it all boils down to the capabilities of your receiver! And you have to read the manual very carefully sometimes in order to figure out how it handles the different signal types.

    As I said on the podcast, these days, powerful processors are cheap and included in even entry and mid-level receivers. So it isn’t as much of a concern any more. Most current receivers, if they have a TrueHD and DTS-HD decoder, they also have enough processing power to apply bass management and room correction, etc. after having decoded the TrueHD or DTS-HD signal.

    You have to check on how even current receivers handle a PCM signal though. Some still won’t touch it and will only send it straight through to the amp section. It’s a weird choice, but I still see it from time to time.

    So in terms of pure audio quality potential, TrueHD and DTS-HD Master Audio are lossless audio codecs. Once they are decoded, they are PCM audio and nothing has been lost from the signal having been coded into TrueHD or DTS-HD MA and then decoded back into PCM. But depending on how your receiver handles the various signals via HDMI, it might be better to set your Blu-ray player to either send the TrueHD and DTS-HD bitstreams to your receiver so that the receiver can decode them, or it might be better to set your Blu-ray player to decode TrueHD and DTS-HD itself and then send the resulting PCM to your receiver.

    In my case, with the 705, it is certainly better to let the Blu-ray player handle the decoding and send a PCM signal via HDMI to the 705 receiver. That way, even if it is high bit-rate, high sampling rate 96/24 audio, the 705 can still apply bass management, room correction, THX and any other digital processing. But if I had a player that will only pass PCM audio straight through to the amp section and won’t apply any processing to a PCM signal, it would be better to send the TrueHD or DTS-HD bitstream from the Blu-ray player.

    No information ever gets sent back from the receiver to the Blu-ray player. It is strictly a one-way signal going from the Blu-ray player to the receiver. Some Blu-ray players, like Oppo’s, allow you to apply bass management inside the player! So that is what Tom was talking about. If you have one of those receivers that does not have TrueHD or DTS-HD decoders – or it has the decoders but cannot apply any bass management to them – AND that receiver will only pass a PCM signal straight through to its amps, then you could have the Oppo Blu-ray player decode the TrueHD and DTS-HD audio AND apply bass management inside the player, then send the result in PCM form via HDMI to the receiver, which will send that signal straight through to its amps and onward to your speakers!

    So it’s a lot of “ifs, ands, and buts”, and sadly, no “one size fits all” solution or advice. You simply have to learn how your receiver handles the various audio signals via HDMI and then set up your Blu-ray player to provide the best signal type for your specific receiver.

  4. Mark
    May 5th, 2012 at 06:19 | #4

    Wow, that’s a good read. Luckily, or unluckily, my receiver is a JVC RX-D201 so my study session won’t be too long.
    Thanks Rob.
    MC

  5. Jeb Butler
    May 5th, 2012 at 12:05 | #5

    Anyone remember back in the days of film cameras, there was discussions of resolution that has to do with what the lens, the human eye and the film were capable of. They all amounted to that 35mm was good enough for any real human eye, and yet it is not hard for anyone that isn’t blind to recognize a print made from a large format film. Bean counting doesn’t necessarily tell the whole story, so I enjoyed discussion on the itunes format and the 48 frames.

    My family and I spend our winters snowmobiling and filming. I can say that while the ridiculous frame rate of the red epic makes for fun slow motion and stuff, it is the crazy dynamic range that makes that camera amazing. It really does approach the way our eyes see the contrast in the winter world and I have never seen that before.

    Jeb

  6. Jeb Butler
    May 5th, 2012 at 12:06 | #6

    Bring on the grammar correction Rob! HAhaaa!

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