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DRM Reduces Battery Life
gr8_phk writes "An interesting article
over at C|Net claims that playing DRMed music can reduce battery life up to 25 percent. Yet another reason to stick with plain old MP3 files." From the article: "Those who belong to subscription services such as Napster or Rhapsody have it worse. Music rented from these services arrive in the WMA DRM 10 format, and it takes extra processing power to ensure that the licenses making the tracks work are still valid and match up to the device itself. Heavy DRM not only slows down an MP3 player but also sucks the very life out of them."
More on these exciting discoveries at 11 (TM).
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The article compares MP3 @ 128kbps, with WMA9 @ 192kbps and WMA10 DRM. Spot the flaw in the methodology yet?
WTF? Do they do a license check after reading each bit?
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Why is this in the apple section? I'm no apple fanboy but the windows DRMs cut battery life by 25% and apple's cut it 7%, seems like this should be in some other category cuz it's actually a bigger issue with plays-for-sure files...
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They don't seem to have tested for that question. If it is the newer formats rather than the DRM, the question arises, "Would you accept a shorter battery life for higher fidelity and/or better compressed files?"
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This is why I play NetHack rather than World of Warcraft.
oh, and because it's free as in beer, too
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If it weren't for every site on the whole damn Internet parroting each other so badly perhaps this never would have made the news. Anyway their "study" is deeply flawed, and while it could be argued that DRM does actually cause your player to consume more battery life than it otherwise would, DRM is not making the power impact they claim and anyone giving the problem more than even five seconds of rational thought would realize this.
The codec is the problem. It takes more power to decode WMA (DRM or not) than it does to decode MP3. Ditto for AAC. The codecs are more computationally intensive and are decoded by general purpose CPU's in many players while MP3 is most often decoded with dedicated ASIC's. Even if all decodes are done in dedicated hardware, the MP3 codec is still likely going to be the most power efficient.
A proper study would have compared identical tracks with identical compression with and without DRM such as an iTunes track played on repeat vs the same track with DRM stripped out played the same way. I'd bet the overhead of the DRM is more on the order of 1-3% here.
It is; however, the DRM that is locking you into using WMA/AAC vs the power-saving MP3 format in the first place, but it's a bit of a stretch to say that it's the DRM's fault that a player running a more complex codec takes a power hit for doing so.
Mp3, as it turns out, is a lot easier to decode than wma and other later-generation formats. The fact that you have to use mpeg4 or wma with your DRMed purchase is just an unwanted side-effect.
That said, it is one reason I only play mp3s on my portable player. LAME has brought a level of quality to the mp3 format that none thought possible, and it keeps up suprisingly well with "more advanced" codecs. I see no reason to use anything else...it plays everywhere, and uses less battery life.
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A good summary of the CNet study is at http://www.cdfreaks.com/news/13193.
The Slashdot headline/summary is a little misleading. The test showed that Apple's FairPlay DRM caused about an 8% battery life penalty. It was the Zen Micro with the WMA DRM that caused a 25% drop in battery life. In this case, (if you HAVE to have DRM'd music), it seems Apple's scheme is the way to go.
Some people have raised the issue that they compared 192kbps WMA files with 128kbps AAC (i.e. iTMS) files. AAC, in general, sounds pretty good at 128kbps. (Geek Disclosure Time): I've run a few double-blind, multi-listener tests, and most people put 128 AAC about equal with 192 MP3 (constant bitrate). I have no idea whether 192 WMA is overkill - if that's what Napster provides, well, I'm assuming that's comparable sound quality.
I'm not an engineer, so I can't say whether or not the bitrate difference could reasonably account for that great a difference in battery drain. I will, however, note that if you choose to use a less-efficient codec, that's your fault.
As everyone on Slashdot knows, playing Ogg Vorbis files actually charges your battery.
When you first open up a DRM file to play it, yes a little bit of processing occurs right then doing public/private key decryption to unlock the RC4 encryption key used to decrease the rest of the file. This however is probably about the same amount of juice as is required to play 1/10 a second of audio. During actual audio playback the players are doing an RC4 block cipher decryption operation. That's a linear time operation on par with generating a modulus for 8 bits. Meaning it's basically nothing compared to the horsepower needed to convert from compressed audio to waveform pcm audio. The article review is a crock of crap.