关于AAC的一些事实

我注意到有关AAC音频格式的错误信息略有上升这可能是巧合,但我怀疑这是苹果近期在iTunes Store上销售无DRM音乐的结果有些人一直坚持认为,苹果公司对iPod和iTunes的宏伟计划取决于专有文件格式的锁定,我认为他们现在所做的是抓住某种方式继续提出这个论点。

史蒂夫乔布斯之后关于音乐的思考“,这些”所有关于锁定的类型“都认为乔布斯并不是说他写的是什么, that Apple renounced DRM solely for PR value, knowing that record companies would never go along — or that Apple would later reveal some sort of fine-print restriction on their offer to sell DRM-free music (like, say, requiring all four major record labels to agree to do it).

上周与EMI的公告让这些论点得以休息。

But why did these lock-in arguments gain so much traction in the first place? One thing is that this — where by “this” I mean using proprietary file-format lock-in advantages as a competitive weapon to bludgeon competitors and maintain a market advantage — is what Microsoft has done for decades你好,Microsoft Office Open XML

Let’s imagine for one paragraph that Microsoft’s and Apple’s digital music positions were flipped: that it was Microsoft that shipped the world-changing Zune in 2001, that they had sold 100 million Zunes to date, and that Microsoft’s online music store had 85 percent market share for legal downloads — all of them protected by Microsoft’s proprietary DRMCan you imagine, in this scenario, Steve Ballmer or Bill Gates publishing an open letter like Jobs’s “Thoughts on Music”? Can you imagine Microsoft volunteering to switch from DRM-protected songs to an unprotected industry standard file format?

我也不。

微软本来会告诉EMI他们坚持使用无DRM的曲目经典的微软,微软有一套球,会告诉EMI,如果他们想出售无DRM的曲目别处,在其他商店,他们突然发现他们的歌曲在市场主导的微软商店改变了条款。

Apple并不是“数字音乐的微软”,每个人都应该停止尝试查看他们的行为,就好像他们一样Alas, that’s too much to hope for, and so in the meantime, now that Apple has proven its commitment to DRM-free music downloads, keep your eye out for anti-AAC propaganda from those pushing an anti-iTunes or anti-Apple agenda.

例如,Giles Slade在本期“琼斯之母”中发表的这篇奇异的文章,“iWaste“:1

These days, the champion of audio obsolescence is Apple, which successfully combined its iPod with a unique digital format (AAC). By embracing a non-MP3 format, Apple locked you into its world. Now, when your iPod breaks, you have a library of music that you can’t use on other players你必须买另一台iPod。

MP3无处不在,是的,但它不是免费的标准包括美国在内的大多数国家/地区的MP3权利由汤姆森消费电子公司持有,公司必须支付这些权利许可费用于播放或编码MP3音频的任何硬件或软件产品Audio playback in hardware costs $0.75 per unit, for example; encoding costs $1.25 per unit.

AAC对Apple来说并不“独一无二”它甚至不被Apple或任何其他单一公司控制或发明它是ISO标准由杜比的工程师发明与Fraunhofer,Sony,AT&T和诺基亚等公司合作许可受到控制通过ViaFor up to 400,000 units per year, AAC playback costs $1.00 per unit; for more than 400,000 units per year, the price drops to $0.74 per unit.

在许可成本,专利和开放性方面,AAC与MP3非常相似MP3 does have the advantage of near-ubiquitous support in consumer electronics and software; AAC has the advantage of slightly better audio quality at the same encoding bitrate此外,MP3需要2%的“电子音乐发行”版权费,AAC不需要分发版税。

是否有人争论MP3 - 从iTunes Store中获取无DRM歌曲的MP3是一个更好的选择,而当从CD上翻录音乐时,它是iTunes的默认编码选择?2当然但是,AAC也有一个强有力的理由:更好的质量和分销费用。

理想的情况是真正开放和免费的文件格式,如Ogg Vorbis取代MP3作为事实上的世界标准没有专利,没有许可费,有文件记录的文件格式,用于编码和解码的开源库然而,这似乎并不存在在现实世界中,大公司似乎只对其他大公司支持的多媒体格式感到满意。

在他被误导的“比你想要了解的音频格式更多” comparison last week on his Zunester weblog, Dave Caulton — who, it’s worth pointing out, works for Microsoft doing competitive analysis for the Zune team — described the licensing situation for WMA as “Freely licensable for a low fee” (where by “freely” he apparently means “freely” in some sense other than “without cost” or “without restriction”)Caulton将AAC许可称为“相对昂贵”,将MP3许可称为“低费用”如上所述,AAC许可并不比MP3贵得多(而且每年超过400,000台设备,实际上每单位便宜一便士)。

但它确实,WMA许可证要便宜得多:每个单元0.10美元用于播放两个或更少的音频通道,每个单元0.20美元用于编码但WMA是行业标准与AAC不同,它由一家公司控制:微软一分钱一分钱:一旦你获得了WMA音频许可,你也可以通过微软获得Windows Media DRM(如果你需要支持DRM)和Windows Media Video的许可费。

另一个思想实验:假设苹果公司选择在2001年将WMA作为iPod的主要格式Do you think it’s possible that Microsoft might have decided to change the licensing terms at some point after the iPod became a phenomenon? Or, perhaps better put: Do you think it’s possible they不会有?

The implication in pieces like Giles Slade’s in Mother Jones is that AAC is somehow an “Apple format”, and that by selling DRM-free tracks from iTunes as AAC files, they’re still pushing a file lock-in strategy with songs that only play on iPodsFairPlay DRM is an Apple format; regular AAC is not这是一系列设备由维基百科列为支持AAC

  • 微软Zune
  • Sandisk Sansa e200R
  • 索尼PlayStation Portable
  • 索尼Walkman S系列播放器
  • 索尼爱立信手机
  • 诺基亚手机
  • Palm OS PDA
  • 微软Xbox 360
  • 索尼PlayStation 3

该列表几乎包括iPod和iPhone的所有重要竞争者,而Xbox和PlayStation至少是Apple TV的竞争对手。


Apple使用AAC代替MP3类似于1998年Mac转向USBUSB was an industry standard that wasn’t taking off because PCs didn’t ship with built-in USB ports, which PC makers didn’t include because there weren’t many USB peripherals on the market, which peripheral makers didn’t want to build because there weren’t enough PCs shipping with USB ports.

然后是iMac,他的只要外围端口是USB(它甚至没有FireWire。)突然间外围设备制造商有理由制造USB设备,之后,PC制造商有理由在新PC上安装USB端口。

Apple使用AAC作为iTunes的默认编码,也让其他公司有理由采用它由于iTunes,有数十亿个AAC编码的音频文件从CD中翻录,否则将被编码为MP3。


更新:根据读者反馈的简短后续文章:“关于AAC,Ogg和MP3的更多信息”。


  1. The crux of Slade’s article is his claim that iPods are “disposable”; Slade claims that “after 13 months of heavy use, the lithium-ion battery of the iPod can lose more than half of its functionality.” Uh-huh有人应该告诉斯莱德Neistat兄弟called, and they want their accusation back. ↩︎

  2. 你,作为那种阅读万博manbetx贴吧的书呆子,几乎肯定知道iTunes有优先设置我正在把这个号码拉出来,但是我敢打赌80,甚至90%的iTunes用户甚至不知道他们可以改变这些设置默认设置是只要settings for most users in a mass-market app like iTunes. ↩︎