The Analog Sunset

November 13, 2013 in Tech Talk by Sam Davisson

Waybackmachine3Back around the first of the year, 2012, the original version of this website crashed and I lost a number of articles that at least I had thought were pretty well done. Some, like this article which was originally written in July 2011, may be a bit dated as the analog sunset pretty much has set it did contain information that is still relevant. So, I’m here to re-post it and add it back into the legacy! 😉

What is the Analog Sunset?

The analog sunset is a part of the Advanced Access Content System or AACS license agreement. AACS is the encryption also know as Digital Rights Management System (DRM) adopted by content owners and device manufactures to protect content recorded on blu ray disk from copying or illegal distribution.

Content owners (ie. movie studio’s) want to limit the analog output from blu ray players, mainly the component outputs as they are the only analog outputs that are capable of producing an HD signal. For some reason, they believe that recording analog component video is easier than simply ripping a blu ray disk. As illogical as that argument is, it is a fact that we AV design engineers have to live with.

The AACS agreement implemented a couple of ways to accomplish this. The first is a hardware limitation mandated to be incorporated by the manufacture of players. This is what is known as the analog sunset. The second limitation may be used by content producers,
and comprise mechanisms known as the Image Constraint Token or ICT and the Digital Only Token or DOT.

Something to keep in mind, is the sun has already started setting. According to the final AACS adopter agreement in June of 2009:

Analog Sunset – 2010. With the exception of Existing Models, any Licensed Player manufactured after December 31, 2010 shall limit analog video outputs for Decrypted AACS Content to SD Interlace Modes only [composite video, S-video, 480i component video, and 576i video].

While this is quoted directly from the AACS adopter agreement, it may seem a little confusing to us mere mortal engineers where it tries to explain what the SD interlace modes are. 480i relates to standard NTSC video, 576i to PAL.

But, as you can see, the first part of the analog sunset has been in effect for about 6 months now. For the AV designer, that means that almost all of the pre-sunset blu ray players are out of the distribution cycle and the output limited ones are now being sold.

So, with the sun sitting halfway down in the western sky, when can we expect the it do dip below the horizon? Again, as defined by the final AACS adopter agreement of 2009:

Analog Sunset – 2013. No Licensed Player that passes Decrypted AACS Content to analog video outputs may be manufactured or sold by Adopter after December 31, 2013.

So we still have a couple of years before the analog hardware option is totally gone. But, keep in mind there are additional limitations that are already incorporated in the AACS agreement that are available to content providers now, the Digital Only Token (DOT) and the Image Constraint Token (ICT). While different both affect the blu ray player and the functionality of the analog outputs and both are defined as follows in the adopter agreement:

  • Digital Only Token shall mean the field, as described in the Specifications, used to trigger the limitation of output of Decrypted AACS Content to only-digital outputs.
  • Image Constraint Token shall mean the field, as described in the specification, used to trigger a Constrained Image as set forth in these Compliance Rules.
  • Constrained image is also defined in the agreement as follows:

    Constrained Image shall mean an image having the visual equivalent of no more than 520,000 pixels per frame (e.g., an image with resolution of 960 pixels by 540 pixels for a 16:9 aspect ratio).

    What I find interesting, using the term interesting loosely, is that a constrained image is of higher resolution and different aspect ratio than defined in the 2011 hardware analog sunset. But we will skip this anomaly, at least for now, and work with what DOT and ICT really mean.

    The Digital Only Token may only be set on blu ray disks that released within the first 6 weeks of the theatrical release or if disclosed on the packaging. This also affects cable or satellite TV only in respect to Video on Demand (VOD) services where content (movies) are available prior to the blu ray release.

    The Image Constraint Token can only be set on disks sold after December 31,2010. There seems to be a “gentleman’s agreement” between content producers and equipment manufactures that prohibits the use of this token until 2012 but since it is a “gentleman’s agreement” is there is no guarantee that disks with the token set will not soon show up. Use of the ICT must be disclosed on the packaging.
    What the Analog Sunset is not!

    The analog sunset only governs equipment licensed for AACS-encrypted content playback and has no authority over the playback of non-blu ray Disk media such as unencrypted media files, presentations, or CDs. Other means of content delivery utilizing a combination of software, hardware, and online services may or may not duplicate the licensing requirements or analog sunset features established by AACS for Blu-ray players. While not governed by AACS analog sunset requirements, other services that offer protected content for download or streaming, may require limitations on analog outputs. But this would depend on the policies of the particular service in question, and whatever agreements the service has with content owners such as the Motion Picture Association of America – MPAA.
    Keep in Mind …

    This affects all analog component outputs of a device capable of AACS encoded playback. That means that not only your blu ray disk player it also includes playing back through the analog output of your computer. Below is a simple table that I could have used to explain all this:

    Video Source Device Content Displayed Analog Output Status
    Blu Ray Disk Player Commercial Blu Ray Disk Standard definition only after 2010, disabled after 2013
    PC Commercial Blu Ray Disk Standard definition only after 2010, disabled after 2013
    PC Protected Content Depends on individual agreements between service
    provider and content owner
    PC Non-Protected Content Unaffected
    Satellite TV / Cable Box Subscribed channels May not be disabled in the US
    Satellite TV / Cable Box Video On Demand In the US, only to be disabled for new services offering
    first-run movies for 90 days or before availability on disk

    Signal to Noise

    November 9, 2013 in AV Design Tips, The Basics by Sam Davisson

    signal-to-noiseI’m still not quite sure why but when I started the basic series with "Power and Grounding" most of the comments, both public and private where that I was setting the stage to talk about audio. Having a solid ground plane affects everything but I’ll concede that in this digital age, it affects audio the most since it is still basically distributed in analog.

    The second most requested topic was signal to noise. The signal to noise ratio, or SNR, of a signal is a measurement of the power in the signal fundamental relative to the RMS sum of the energy of all in-band noise components excluding harmonics.

    From an integration perspective I never give the SNR (signal to noise ratio) a second thought. The reason being is that IF you have a solid grounding system and IF you’ve built your cables correctly and IF you have minimized the distance of your unbalanced analog audio runs, then the worst case scenerio for SNR (and it’s cousins THD & SND) should be that as the lowest SNR rated equipment specified in the system. In other words, it’s a design consideration not an integration issue. But IF it’s not integrated properly, your going to be able to hear it, even with slightly poor hearing. As a consultant, my specifications do not even require testing for these.

    From a design perspective you need to answer the question, for yourself, of how much noise is too much noise for the system in design and then specify products that meet those requirements. For me, if I’m designing a performing arts center or music recording studio then I’m looking at a SNR of 110db or greater. A classroom or conference room, typically a SNR around 75db and a executive board room or auditorium which will support the spoken word, a SNR above 80db.. But these are almost arbitrary numbers that I’ve come up with based on customer interaction and satisfaction. There is no science behind them.

    Constant Voltage Speaker Systems

    November 3, 2013 in AV Design Tips, The Basics by Sam Davisson

    overhead-speakerWhile this might be a great reminder of how much technology has changed, I’m not sure why when I searched for an interesting image of overhead speakers this image came up. Can I assume that in Google’s eyes this instructor is teaching something that is way over the heads of the students?
    Or, perhaps even, that should something catastrophic happen and we had to revert back to "old tech" people would be completely lost? But this has nothing to do with furthering today’s topic, Constant Voltage Speaker Systems.

    Electrical power companies figure out a long time ago that the best, most efficient way to distribute power was to step up the voltage at the power station and then to step down at your house. The audio industry took this model for distributing audio to large numbers of speakers or speakers no where close to the amplifier which gives us the constant voltage system we currently use or over use but I’ll probably discuss that at some later date.

    The term “constant-voltage” is somewhat misleading causing some confusion. In electronics, two terms exist to describe two very different power sources: “constant-current” and “constant-voltage.” Constant-current is a power source that supplies a fixed amount of current regardless of the load; so the output voltage varies, but the current remains constant.

    Constant-voltage is just the opposite: the voltage stays constant regardless of the load; so the output current varies but not the voltage. Applied to distributed sound systems, the term is used to describe the action of the system at full power only, an important point in understanding. At full power the voltage on the system is constant and does not vary as a function of the number of loudspeakers driven. As long as you do not exceed the maximum power limit of the amplifier you may add any number of speakers and the voltage will remain constant.

    The other thing that is “constant” is the amplifier’s output voltage at rated power – and it is the same voltage for all power ratings. Several voltages are used, but the most common in the U.S. is 70.7 volts rms (100 volts is common outside the US). The standard specifies that all power amplifiers put out 70.7 volts at their rated power. So, whether it is a 100 watt, or 500 watt or 10 watt power amplifier, the maximum output voltage of each must be the same 70.7 volts.

    Advantages of 70V Systems

    A 70V line reduces power loss due to cable heating. That’s because the loudspeaker cable carries the audio signal as a low current. Consequently you can use smaller-gauge loudspeaker cable, or very long cable runs, without losing excessive power.

    Another advantage of 70V operation is that you can easily provide the amplifier with a matching load if you’re connecting hundred of loudspeakers. With a single 8-ohm amplifier output it can be difficult to wire the loudspeakers in a series-parallel combination having a total impedance of 8 ohms and if one loudspeaker fails, all of the loudspeakers in series are lost. This changes the load impedance as seen by the power amplifier.

    Conversely, with a 70V system you can hang hundreds of loudspeakers in parallel on a single amplifier output. In addition, a 70V distributed system is relatively easy to design and allows flexibility in power settings meaning different speakers can be set to have differing volume settings.

    Disadvantages

    Simply, your audio quality suffers, especially in the low frequency range, transformers can degrade the frequency response and add distortion. Also, designers have gotten lazy. Ceiling speakers are thought of only in a 70V configuration and used to fill a room with noise rather than doing a proper LCR (left, center right) 8 ohm sound system with 8 ohm ceiling speakers for speech reinforcement.

    Yes it may be cheaper but isn’t the goal natural sound.

    Opinion

    This is my strictly my opinion. Constant voltage systems are great when used as intended, as a means of connecting a large number of speakers where needed or in remoting speakers a long way from the amplifier.

    But this technology is being over used because of simplicity. A design engineer doesn’t need to understand how to fill a room with sound. Clients and the industry suffers because of this.

    I’ll leave you with this little chart on cable requirements I borrowed from Belden Cable’s article on this 70V systems:
    Speaker Cable Distance Chart

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