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设计师分享iPhone游戏音效设计准则

发布时间:2011-06-06 08:30:06 Tags:,,

作者:PJ Belcher

自从iPhone在全球热销,iPhone应用也开始繁荣发展,游戏应用尤其如此,有些销量甚至堪比AAA巨作。主流游戏开发商纷纷把iPhone视为现有产品的推广平台,甚至决定为该平台量身打造游戏产品。

对于独立游戏开发者来说,iPhone也是个重要的开发平台。因为其拥有庞大的用户群,所以该平台的游戏很快就能从小众需求变为大众产品。

新机遇的出现,为那些刚刚从经济衰退中复苏的人们开启了新的冒险旅程——在商机无限的信仰感召下,新开发者们建立新游戏公司,着手制作新平台的游戏。

独特的界面、庞大的用户群、强大的可接入性和应用软件属性(“短简精”、可玩性高的游戏应用)等得天独厚的条件,为iPhone游戏的开发创造了无限可能。

目前,游戏质量的门槛如此之高,要在iPhone这样的“娇小”的设备里安装如此“壮硕”的游戏应用,想必不是件易事。更确切地说,游戏音频设计者将面临怎样的挑战?

除了所有游戏都存在的音频设计难题,在常规进程当中还面临着一系列附加难题和特殊难题。如果说这只是给游戏音效设计工作增加了一点难度,那么,信息不足就确实是设计者们面临的艰巨考验了。

要通过这个考验,iPhone音效设计者应该明确自身所面临的挑战、克服的办法和iPhone游戏音效的含义。在本文,我将探究设计者应该明确的设计依据、音效对软件的影响、技术难点、iPhone要解决的特殊难题,还将涉及用户行为、iPhone音频开发应用类型等方面。

以上也是我在与iPhone音效设计工作打交道过程中遇到的问题,并且我依次(但不是所有)找到了解决方法或者做出解释说明。我希望能将自己的经验与其他开发者分享。

那么,有效的iPhone音效设计到底要具备什么?动态音景、浸入式声道和高明的创意——这些只是增加一点点难度。

众所周知,iPhone与其他平台相比有许多自身特点。从用户界面到用户特点,不止是不同,甚至到达了天差地别的程度,所以就产生了一些需要深思熟虑的设计要素。音效设计也不例外。我希望读者通过阅读本文的下半部分,了解作为一名游戏开发者应该明确的设计考虑。

ios_iphone4(from gamasutra.com)

ios_iphone4(from gamasutra.com)

资产大小

iPhone音效制作者最大的关切莫过资产大小。不过这个话题的范围太广,恐怕无法在一篇概要里完全解释清楚。(游戏邦注:作者在另一篇文章”Audio for iPhone: Size Matters”里也谈到了这个话题)以下内容主要是为读者阐明开发者面临的挑战。

苹果的无线传输大小限制是20MB,这意味着,如果不通过Wi-Fi,而是通过3G服务下载,那么所下载的应用大小不能超过20MB。这种大小限制对iPhone应用病毒式营销的有效性来说至关重要。

如果潜在用户必须找一个Wi-Fi网络热点(能够访问Wi-Fi网络的地方),或者等到回家再购买应用,那么这个销营过程就被破坏了,所以20MB的上限十分必要。

顺带说一下,如果完整版应用大小超过20MB,但仍然允许通过3G服务出售简化版,有DLC(追加内容下载包)就便利多了,因为DLC可以添加到新买的应用上。

考虑到音频资产的大小,缺少文件空间对音频制作者而言已经是个很大的挑战了,更别说与其他制作文件竞争空间了。你最多能指望占到50%,也就是10MB。在这种困境下,浸入式、动态、创新的音轨看似很棘手吧?这相当于你说服正在制作这款游戏的其他人相信你的理念占了整个游戏价值的50%!

怎么?难度太大了?记住,你要把这活当成你的最后一份工作好好做,所以别半途而废或是草草应对挑战。迎难而上,做出更上乘的音效才是王道。

iPhone在这个资产大小的问题上同样犯难,因为它在任何时候都只能解码一个压缩文件,这意味着大多数的音频(除了一些精选以外)都不能做成压缩的PCM格式(这种格式相对比较大)。但有不少方法可以缓和这个缺陷,如使用文件基础生成音频设备、交叉淡入淡出循环技术、精选渲染效果。

我最近还想出另一个巧妙的方法。压缩格式通常不能循环,因为在压缩过程中,音频文件的前后都被补上“填料”。正常情况下,这意味着音频不应该是压缩的,但我最近学会使用一个移除“填料”的程序生成无缝循环的MP3。

这个软件的具体工作原理我并不清楚,想知道就Google一下吧。我过去曾使用“Compu Phase”编制成的这类应用软件——但PCM格式的音频大多需要源文件。这个软件能有效地移除未压缩文件格式的源文件请求,这点很重要。

除了这个方法,Apple文件详述了这么个系统,允许你以编程的方法移除“填料”,从而达到无缝循环。这个方法的缺点就是需要额外编码,但这也就是说,你可以使用M4A(AAC)编码,在低比特率下,M4A的音效确实比MP3好得多——至少我个人这么认为。

环境问题

那么,iPhone应用的制作重点是什么呢?这些问题在其他游戏音频中也存在,只是在移动设备市场显得更重要,因为玩家听游戏声音的方式不尽相同。听声音的方式不同是因为玩家的游戏环境和播放形式不同。

一般来说,玩家的游戏环境不外乎卧室或者客厅,使用的设备也就是电视扬声器或家庭影院。而对于iPhone就不是这么一回事了——从厨房到公交车,设备从内置喇叭到任何玩家能接入的东西,都有可能是玩家的游戏环境。

我们不妨做一些假设——在满足音频运行要求的环境下,大多玩家只会使用内置喇叭(iPhone 、 iPod 和iPad的音效是不同的)或者耳机(每一款Apple产品之间的音效差异非常小)。

尽可能在游戏中或者设备上测试音效。在游戏中的音效测试非常重要,你应该已经测过了吧,iOS设备尤其需要测试。如果能用上录音室专用的监听设备作测试,那你大概可以听到天籁之音了。不过,Apple耳机能不能产生符合要求的音效,就是另一回事了。

请记住,要在不同的设备、不同的环境中(厨房、巴士、公园甚至是洗手间)、有无耳机等的情况下测试游戏音效。显然,在这么多情况下,不可能有哪一种完全达到要求的,所以关键就是在这么多条件下取得最佳中间点。

移动设备

我第一次摸到iPhone时,我的第一个反应是:屏幕的触感不太好,或者说缺乏触感功能的界面设置(除了主页铵钮)。稍后我会更详细地讨论触感的问题。我之所以现在就提出来是因为触感的缺乏往往要靠某种反馈来弥补,而这个重任恰恰就落在音效上(因为玩家的手指挡着屏幕,所以很难看到按了什么键)。

大多情况下,对玩家按键的再次确认反馈就是发出悦耳的“叮”或“砰”的声音,但这种声音必须让用户听到。iOS的菜单选择声的音效还是很不错的。内置喇叭发出的声音主频很容易再现,总体音效又不会被喇叭反复发出的频率所掩盖。

也就是说这个“叮”声是作为一个小过渡——这种声音不会被切断也不会失真,更说不上难听,而且还很入耳。在耳机的条件下也一样。作为音效师,你可以好好利用这个特点,不过还是不要忘了所有设备都是不同的。

因为小喇叭(耳机或内置式)的特性,精确的声音播放长度难免受限。大多的低频率声音是根本无法播放的。如果硬要这么做的话,就不得不牺牲高频率的音质。

最好的办法是,把iPhone声音的最大频率值上限变小。大多音乐缩减频率20到70 Hz就能听得出来了,但考虑到播放的可能形式,这个缩减量还得往上提。尽管缩减低频可以“存活”高频,但除此之外就没有任何好处了。这么做还会引起音量峰值的增加,无论你使用什么数码音频工作站软件都是这样的。所以还是小心剪辑为妙。

最后一点是音量能力(在不失真的情况下能达到多大的音量)剪辑。所有设备都存在谐声共振失真的现象,无论是回放大音量还是某个频率。如果玩家一直调高设备音量,内置喇叭放出的声音就会失真。如果玩家是在比较喧闹的环境下使用设备,那么失真的现象就很普遍了。这未必就是玩家的错,不过音效听起来很差倒是不假,而且也损害了整个游戏的形象。

不幸的是,我对这个问题也是不知所措啊——因为这是设备本身的问题。我们能做的就是减小最大音量,直到某个点上,在这个点上音量峰值不会引起破音或失真,不过这么做的话,当前游戏可能比其他处于同一音量值的游戏要安静得多。也难怪这会被看成是缺陷了。

我能想到的唯一一个行得通的办法就是,允许音量在正常的范围内增大,且音量能达到的峰值也是正常的上限。这个办法也不是尽善尽美的,但好歹是个方案吧。

我给iPhone制作音效的惯用工具不外乎标准的DAW软件。能编写、能录音、能生成、能混音、能剪辑、能优化、能编码和能采样,这就是你所需的所有功能了。我本人一般是使用Logic Pro (只用这款软件的时候越来越多了)和 Cubase(游戏邦注:它是集音乐创作、音乐制作、音频录制、音频混音于一身的工作站软件系统,由德国Steinberg推出)就能做好所有工作了,不过其实任何带编码器(要好一点的)和采样功能的软件就我够用了。

我用Logic Pro(由Apple推出的业内领先的音乐创作和音频制作软件)挺顺手的,是因为苹果的M4A编码器很好用,MP3编码器也不赖(游戏邦注:iPhone开发工具Unity 3不再支持M4A了)。

还有其他专门的采样软件包,也是有用的。

我个人只使用Logic Pro,各位只要使用自己顺手工具就好了(当然,得保证这个软件会做比挑拣采样更复杂的工作,我通常采样声音文件的频率是从44.1Khz到24Khz)。

除了这个软件,我很少再使用其他软件了——我觉得没必要把创作过程复杂化,软件的切换总是会增加创作时间。

只要你能满足开发者的要求,使用什么软件都不要紧。通常情况下,我预期可交付的成品和我实际做出的成品出路不大。我上交的所有声音和音乐都是未编辑、标准化的PCM文件格式,频率至少是44.1Khz。

这样我所交出的文件就能达到游戏的要求了,文件的采样/编码版本是混音和编辑过的。除此之外,我会提供一个技术文件,详述各个样本的用途、解释使用目的、使用方向、文件名等和所有可能用到的特殊细节。

就各个开发环境如何不同方面而言,差别很小。我前面提到Unity 3不再支持M4A,所以如果这是默认的文件格式我就会使用,但如果客户使用的是Unity 3或者自己创建的开发工具,我就会改用MP3格式或者ogg格式(游戏邦注:它是一种新的音频压缩格式,普遍使用于预订的开发环境)。

我使用过的所有开发工具都要求任何要在3D空间播放的声音都必须有单声道声音文件,但基本上所有平台都是这样的。顺便提醒一下,大多数Mac用户没有办法打开Word DOC文件,所以我通常以简单的text文件格式发送优化兼容性的内容。

iPhone作为移动游戏设备推向市场,我前面提到过,你必须认真考虑iPhone的使用地点。这个问题对许多设计过程都有重大影响,音效设计也不例外。最后别忘了尽量多选几种设备做测试。

iPhone games(from ec-base.net)

iPhone games(from ec-base.net)

我们知道iOS设备各不相同(iPad, iPod, iPhone)和有什么不同,但你知道他们的界面有什么不同吗?界面对iPhone游戏设计有何影响?其实所有游戏的设计原则都大同小异。

iOS的独特之处会影响玩家的行为,这些特点是:拥有六维加速器、主界面是触屏、屏幕较小,最重要的是,它是个面向广大用户群体的移动设备。

拜这个独特的用户界面所赐,玩家终于被迫学习与新技术的互动方式——这也是开发者的设计内容。但这对音效设计意味着什么?与视觉效果这个主角相比,游戏的音效时常充当的是无名英雄的角色。如果玩家还是在吵闹的环境下玩游戏,那就别指望玩家能听到无名英雄的声音了。

更惨的是,大多数玩家怕吵到别人,所以就调低音量;因为使用耳机只有玩家自己能听到声音,这显然不符合社交需求,所以玩家很少会使用耳机——正是这种设备的可用性和普遍性限制了无名英雄出头的机会。与他人分享游戏、把游戏转手给他人玩、随便在一个地方和别人一起玩,正是这种增强的社交需要使无名英雄的地位一低再低,最后终于被封杀(关闭)了!

在头戴耳机的情况下,玩家很可能一边听音乐(说到底就成了个iPod),一边玩游戏。我第一次注意到这种行为是在新游戏初测时。如果玩家发现自己的游戏打扰到别人,玩家就会调低音量。

玩家向别人展示游戏时,通常会消音后把设备给别人;在已经很难得到音效反馈的情况下,我发现我自己和其他玩家都没有意识到声音的存在。这真是太令人沮丧啦。说到底,成千上万的人在玩你的游戏,听到了什么、有多少人在听,是无从知晓了。但是任何加强音效的游戏,都更可能给人留下深刻的印像。

如前所述,因为iPhone界面如此独特,所以有几个设计问题要考虑到。我首先注意到的是iPhone的所有控制都缺乏触感。作为互动联系的两个主要方式,触屏和加速给用户的反馈却相当有限。所以操作问题就变得棘手了——因为用户的每一个操作未必都有反馈,所以用户就不断地质疑他们的操作是否已经被设备接收。

一个真实的按钮有这么几个特点:物理移动受限(固定在设备上)、不用看就能识别它的位置及与其他键区分开来(在游戏中这个特点非常必要)。另外,在画面和声音的结合下,所有交互作用都能在游戏中得到加强。

就最基本的层次上讲,游戏只是对玩家交互作用的正反应,但iPhone把一切都改变了。因为玩家只有通过触屏才能知道碰到了什么、发生了什么,但通常要看的地方都让手指挡掉了,人机交互过程就是样被复杂化的。

小屏幕就这样阻碍了设备对玩家的反馈;而加速器的存在,意味着屏幕会四处移动。在这种情况下之下,玩家只能指望声音来指点迷津了。你看看,声音的作用就在于此!

综合考虑到以上所有要点,和开发者共事确实要处理一大堆问题。开发者(除非是我指导音频设计工作)往往列出一份清单,上面列出音效、音乐、环境声音等他所需要的声音,还会标明预期用途、运用位置和长度(是否循环)另外还附上一个简短的效果描述。

一般来说这么做没什么不好,但把这份清单运用于iPhone音效设计就会产生几个问题。如,我需要五个一分钟的循环音乐片段,每一个片段都是相同的长度、循环、环境声音,且每个都要在不同的主题中同时演奏。这个摘要描述得相当合理,不过在iPhone上是行不通的。

首先,在磁盘上,一个一分钟长度、频率为24Khz的PCM文件大小是5.8 MB。所以单单是音乐加环境声音就已经达到58MB了,这大大超过20MB的无线传输限制了。假设不需要考虑资产大小,处理这么大的文件,存储器的工作也是相当繁重了。

所以你要压缩文件了,是吧?还是算了吧,iPhone每次只能回放一个压缩文件。在这种条件下,环境声音和音乐要同时播放的话……成不成问题,你懂的。

怎么可能没有解决办法呢?每个问题的解决办法我都提过了,万事俱备,只欠东风——执行方案就是最后的挑战了。显然音效设计需要明确方向、详尽计划和周全思考,而不是大部分人都指望的那样——只盯着一份音效清单就开工。

更恶劣的是,音效往往是在游戏开发的最后阶段才添加上去。“我们现在要开始第一次测试了,把音效加上去吧”,这种想法行不通。音效现在已经是游戏设计和开发的一部分,不再是孤立的环节,所以通盘考虑是必要的。因此,游戏开发者们,叫音效设计师从头到尾都要参与工作——音效设计师们,准备接受挑战吧。

如果非要列出一份音效清单的话,我会要求玩这个游戏然后再自己列出清单。这不是因为我自视甚高,而是因为音效就是我的专长,并且如果能从头开始做设计,执行各种设计要素肯定容易得多。

我这么说绝不是叫你抛掉开发者列的那份清单。相反地,你应该按清单来做——只是别那么盲目罢了。加上声音生成系统、结合资产、压缩等技术,音效会更好,不过这些技术本来对音效设计就很重要了。这些通常是开发者不会想到的要求。

为什么开发者想不到?iPhone音效设计又不是他们的专业,而是音效设计师的工作。在独立游戏开发者带领的小团队中,作曲家和声音设计师也得充当监督、设计师和领导者。在iPhone游戏的开发过程中,一个人搞定iPhone的游戏音效,这类人简直成了单人乐队中的多面手了。

其他考虑要素

我想返回用户行为的话题——如何促成病毒式营销。就iPhone而言,病毒式营销方式发挥了重要作用。这得归功于iPhone作为移动设备的特性、简单的网页链接能力和低廉的应用价格,iPhone无处不在也就不足为奇了。要让别人知道你在玩什么,发出声音最管用。不像画面,别人得看到了才知道你在乐呵个什么。

就已经树立的品牌来说,这不难,因为大多响当当的图标已经成为品牌的一部分了,所以声音和品牌不费吹灰之力就能认出来了。开发新产品,创建品牌是最讲究技巧的部分,而声音则是关键特征。记着这点吧,你会发现声音如何在游戏之外的世界大展身手。

iPhone的游戏类型不胜枚举,有相当多是在现存的类型基础上开发出来的,也有不少是新作品。各种游戏纷纷在iPhone平台上扎营,有些是从其他平台移植过来的、有些是专为iPhone平台开发的,有些在制作上则对设备要求欠考虑。有些游戏运作得不错,有些就不太乐观。就数量上看,很可能早就大大超过5万个游戏了。就音效来说,所有游戏都有音效,只是上乘之作不多。

还是这个道理,成功的iPhone游戏已经把质量的门槛提得太高了。所以,音效显然必须配得上高标准的游戏。尽管这种挑战看起来太棘手,但也绝对不是无法应对的——所以,迎难而上吧,有超级游戏就有卓越音效!(本文为游戏邦/gamerboom.com编译,如需转载请联系:游戏邦

iOS Audio Design: What Everyone Needs To Know

by PJ Belcher

Since the launch of the iPhone, apps have been big, especially in the games sector, which has seen some sell like AAA titles. Major developers have added the iPhone to their list of available platforms for existing titles, as well as moved to develop unique titles just for it.

It has been a great platform for the indie developer too, thanks to its great accessibility, seeing games from very small groups of people reach huge audiences.

New opportunities have been opened up for people left in the wake of the recession to start their own developer ventures, setting up new companies and designing games, knowing there will be an audience for them.

It is the mobile nature, unique interface, huge number of users, great accessibility to developers and the nature of the “app” (short, simple, high quality games with a focus on playability) that has been incredibly useful to many developers.

With games being so large, though, and the bar for quality being set so high, what challenges does fitting such a big game in a tiny device involve? More specifically, what does this entail for the “audio guy”?

Aside from the normal list of challenges facing sound in any game, there are an added series of problems to overcome and unique issues facing some routine procedures.

This makes everything just that little bit harder, and to add to the confusion is the huge lack of information available to audio developers.

What this feature hopes to achieve is a clearer understanding of what challenges the iPhone audio developer faces, how to overcome them, and, in fact, what game audio on the iPhone really means. In this article, I go into the design considerations you should make, how this affects the app, what technical concerns there are, what unique iPhone issues there are to overcome, aspects of user behavior, hardware concerns and the iPhone app as a genre.

These are all issues, problems, and topics I have encountered while developing audio for the iPhone and, in turn, (but not in all cases) have found a solution or at least some explanation for, which I hope to now pass on to other developers.

So what does it take to produce effective audio for the iPhone? Well, everything it takes to produce good audio for any game: dynamic soundscapes, an immersive soundtrack and great innovation — only with a few added challenges thrown in for good measure!

You see, the iPhone is different from other platforms in a number of unique ways. Anything from the user interface, to the user him- or herself, is wildly different and far more diverse, leading to some very careful design considerations. The audio is no exception. Over the next few paragraphs I hope to shed some light on what these considerations should be and what you can do as the developer.

Asset Size

Possibly the biggest concern of any audio producer for the iPhone will be asset size. The scope of this topic is too large to fully address in this feature, but I write about this in more detail in my article “Audio for iPhone: Size Matters.” The following, however, should give you a good grasp of what developers face.

Apple has an over-the-air size limit of 20 MB. This means in order for the app to be downloaded over 3G and not Wi-Fi, it must be under 20 MB. This is crucial to ensure good sales given the value of viral marketing in selling iPhone apps. The process is broken if the potential customer has to go and find a wi-fi network or wait until they get home to purchase an app, so under 20 MB is a must.

By the way, don’t forget about downloadable content (DLC), which can be added to the app after the initial purchase. This is handy if your app has to go over the limit for the full version, but still lets you sell the lite version over 3G.

This lack of asset space is hard for the audio producer given the size of audio assets, not to mention fighting with other assets for space – -you are looking at a maximum of 50 percent, leaving you just 10 MB. Does that immersive, dynamic, innovative soundtrack seem tricky yet? This is assuming that you convince the other people working on the game that your ideas are worth 50 percent of the game!

Remember, you are only as good as your last job, so don’t back down or produce sloppy audio in light of the challenges — instead, produce even better audio in spite of the challenge and really impress.

The iPhone doesn’t really help matters much either, since it can only decode one compressed file at any time, meaning most of your audio (aside from a few careful choices) has to be in un-compressed PCM formats, which any producer will know are rather large. There are lots of techniques that can be applied to mitigate this, though, such as asset-based generative sound systems, crossfade looping, and carefully selected bouncing; all of which I cover in detail in my above-linked article.

I also recently came across another neat solution. Compressed formats, in general, cannot be looped, due to the “padding” added to the top and tail of all audio files by the compression. Normally this would mean the audio would have to be uncompressed, but I recently learned of utilities that will remove the “padding” and produce an MP3 that would in fact loop seamlessly.

Exactly how it works I don’t know, but a quick Google search should reveal what you’re looking for, I have in the past used one created by “Compu Phase” — just remember most require the source file in PCM format. This effectively removes one requirement for uncompressed file formats; something you will find crucial.

In addition to this, the Apple documentation details a system that allows you to programmatically remove the padding and achieve seamless looping. This has the disadvantage of additional code, but does mean you can use M4A (AAC) encoding, which at really low bit rates does sound much better than MP3 — in my opinion at least.

Environmental Issues

So what about production concerns and the iPhone App? These concerns are part of any game audio, but more predominant in the mobile device market because how the player listens to a game is hugely varied. This is due to the unique environments in which the user can be found, as well as forms of playback available to the player.

Normally it’s the bedroom or living room: played over a TV’s speakers or some home cinema system. Not for the iPhone — it’s anything from the kitchen to the bus, from the in-built speaker to whatever the user decides to plug into.

Game Advertising Online

We can make some assumptions, though; most users will use either the in-built speaker (which produces a different sound from iPhone to iPod to iPad) or the earphones provided (which vary minimally between each Apple product) you can cater your sound to work in these environments.

Always test your sounds in-game on the device. Testing your sounds in-game is crucial and you should already being doing this, but iOS devices particularly require it.

You can produce the best sounds in the world on a set of studio monitors, but whether the Apple earphones will do them justice is another thing.

With this in mind, test your game on several different devices, in different environments (kitchen, bus, park, toilet…) with and without earphones, with headphones, etc. Obviously one way of mixing isn’t going to suit all these criteria; the key is to find a good middle ground in the most common of setups.

The Device

The first time I got my hands on an iPhone one of the things I instantly noticed was the lack of tactility in the screen, or any of the interfaces for that matter (aside from the home button). I cover this in more detail later, but it is worth mentioning now that this lack of feeling calls for an increase in feedback to the user, which is often the job of the audio (especially since whatever is being pressed can’t be seen due to it being obscured to the user’s own finger).

In most cases this comes in the form of a nice tick or pop, re-affirming the user’s action, but this must be audible. The menu select sound of the iOS does a really good job of this. By working with the in-built speaker, the sound’s dominant frequency is easily reproduced and the overall audio isn’t drowned by frequencies the speaker would struggle to reproduce.

This means the tick is reproduced as a nice short transient — it doesn’t clip or distort, it isn’t nasty to listen to, and easily reaches the user’s ear. The same applies to earphones. As the audio producer you can use this to your advantage, although bear in mind that all devices are different.

Due to the nature of the tiny speaker (earphones or built-in) the spectrum of accurate audio playback is incredibly limited. In the case of most low frequencies, they are not capable of being played back at all. The speaker attempting to do so will sacrifice the quality of higher frequencies that it should otherwise be able to playback.

The best way to help this is to have a low cut in your mix before putting on the iPhone. A cut for most music at about 20 to 70Hz is generally sensible, but this can be increased further for iPhone given the possible forms of playback. It is worth noting though that cutting the low frequencies will allow the higher frequencies to “breathe”. This can cause an increase in peak volume and will be true in whatever digital audio workstation software you are using, and in physical playback, so be wary of clipping.

My final point in terms of production is high volume clipping. All of the devices will have harmonic resonance distortion, from playback at high volumes and from certain frequencies. This means that if the user turns their device all the way up, it will result in distortion from the built-in speaker. Given the noisy environments in which the devices are used, this is often the case. It is not necessarily the user’s fault, but it does make the audio sound bad, and, in turn, the game looks bad.

Unfortunately, I have no solution for this — it is an issue that lies with the devices. One way around this is to reduce your overall mix, until you reach a point whereby peak volume does not cause cone break up, and in turn distortion, but this will make your game much quieter than other games playing at an equal level, in terms of volume setting. This can often be considered a negative feature.

My only feasible answer to this would be to allow the volume to increase as it would normally and then apply a ceiling, in which the volume would eventually reach a peak volume, before clipping. Not perfect but a solution nonetheless.

The tools I typically work with to create audio for the iPhone will generally not go beyond standard DAW software. Providing you can write, record, produce, mix, edit, optimize, encode and downsample then that is typically all you will need. Personally I will use Logic Pro and Cubase (increasingly just Logic Pro) to do everything, but any software with a decent encoder (good production tools of course) and downsampler will do.

Logic Pro works well for me because, also having been created by Apple, it has a very nice m4a encoder, as well as a top notch mp3 encoder (it is worth noting here that Unity 3, a popular iPhone development tool, no longer supports m4a.) There are other dedicated downsampler software packages available, which can be of use.

Personally I will just use Logic for this, but only your ears will tell you if it is doing a good job, just make sure it is doing something more complex than just picking out every other sample (I will often downsample sound files at 44.1Khz to 24Khz just to ensure this).

Beyond this I will rarely use any other software; I feel there is no need to complicate your creation process, and hopping between softwares will often increase you production time.

Providing you can give developers what they ask for, then it doesn’t matter what you use. Typically, my expected deliverables and what I deliver are pretty similar with each job. I will hand over all sounds and music in unedited, normalized PCM file formats at at least 44.1Khz.

With this I will hand over all files as they are intended for the game, so downsampled/encoded versions of files, that are mixed and edited. In addition to this I will supply a technical file detailing what each sample does, explaining its intended use, where it goes, file name etc and any other specific detail that may be required.

In terms of how this varies from each development environment the changes are minimal. As I mentioned earlier Unity 3 no longer supports m4a, so although I would use this file format by default I would instead have to use mp3, or ogg (popular in bespoke development environments) for clients using Unity 3 or a self-developed dev tool.

All development tools I have encountered will require mono sound files for any sounds to be played in 3D space, but this is often true of any platform. One a different note, most Mac users will not have the capabilities to open Word DOC files, so I will often send text in plain text file formats for optimum compatibility.

The iPhone is marketed as a mobile gaming device, so as I mentioned earlier you need to carefully consider where it will be played. This will have strong influences on many design considerations from all aspect of development and audio is no exception. Finally don’t forget to test on as many devices as possible.

We know of the various iOS devices (iPad, iPod, iPhone) and how they vary from each other, but what about how their interfaces vary from other devices? How do they affect the design of an iPhone game? Well, there are all the same principles of designing any other game, only with a few extra challenges thrown in (again!)

The iOS devices are unique in several ways, which all have an effect on user behavior. It has a six axis accelerometer, the main interface is a touch screen, the screen is tiny, and above all it is mobile, possibly a phone, and open to a wide audience of consumers.

Thanks to this unique user interface, players are forced to learn a new way to interact with their technology — and you as the developer has to design this. But what does this mean for the audio design? Compared to visual impact, the sound in any game is frequently an unsung hero, and given the often noisy uncomfortable environments in which the game could be played, it often never gets heard by the player.

Furthermore, most users will turn off the sound so as not to disturb others, and will seldom use headphones due to their unsociable nature. It would seem that making the device so accessible is a problem for the game’s audio. You can easily share a game, pass it to others, play it pretty much anywhere and with anyone, and it is this increased social nature that makes the sound get turned down, or, even worse, off!

In the event that the user is wearing their headphones, they are likely to either be listening to their music (it is an iPod at the end of the day) even whilst playing a game. I first noticed this behavior while beta testing a recent game. People would turn the sound down to avoid disturbing others, or, if they couldn’t already hear it, not even be aware of its existence.

People presenting the games to others would often hand over the device muted, and in a world in which it is already hard to obtain audio feedback, I found myself with users not even aware there is sound. This can all seem very disheartening, but at the end of the day anything from tens to millions of people will play your game and how many of these listen is unknown. However, those that do will be impressed, reinforcing the role that audio plays in any game.

As I mentioned earlier, the interface on the iPhone is unique and as a result several design considerations need to be made to address this. One of the first things I noticed about the iPhone was the lack of tactile nature about any of its controls. The touch screen and accelerometer, which are the two main forms of interfacing, give the user very little feedback. This makes operation very tricky — since each action does not necessarily have a reaction, the user constantly questions whether their interaction was received, or did what they wanted.

A real-life button does several things; it physically moves, has limits, and you can distinguish its whereabouts and differentiate it from the other buttons without looking at the device, something often necessary in gaming. On top of this, all interaction is reinforced in-game, with visuals and sound.

At its most basic level, a game is a simple positive reaction for the user’s interaction, but the iPhone changes all this. To further complicate things; since the touch screen is your only way to see what’s happening as well as being what you touch, often what you need to see is then obscured by your finger.

All attempts to inform the user of the touch outside of the button are therefore hindered by the small screen and using the accelerometer means the screen moves around. This leaves the only available space in the sound. As you can see the audio has a lot resting on it!

Taking into account all of the above-mentioned considerations, working with developers can produce a number of issues to address. Typically a developer (unless I am directing the audio) will send a list of the sound effects, music, ambiences, and any other audio they want, with details of their intended use, placement in-game, length (and whether music needs to loop), and a short brief describing how it should sound.

Normally this would be fine, but on the iPhone this presents several problems. For instance, say I’m requested to make five one-minute-long pieces of looping music, each with an equally-sized, looping, ambient track to play simultaneously on different-themed levels. As far as briefs go this is pretty reasonable, but it wouldn’t work on the iPhone.

To start with, on disk, a one-minute-long PCM file at 24Khz is 5.8 MB. So the music and ambience alone amounts to 58 MB. This is already well over the 20 MB over the air limit. But let’s assume you’re not fussed about asset size; it is still going to take some heavy memory management to deal with those files.

So you compress them, right? Nope, the iPhone can only play back one compressed file at any time. In this case, ambience and music need to play simultaneously… And so you can see the problems that ensue.

These are by no means impossible to overcome. There are solutions to each of these issues mentioned earlier; the challenge is implementing them. The audio clearly requires more direction, planning, and thought than most will expect, and simply catering to a list of sounds is not an option.

To make matters worse, audio designers are often asked to produce the audio at the end of development. “We’re now about to start beta testing and need to get some audio in,” is not going to work. The sound is now a more integral part of the game’s design and development than ever before, and it will only work if carefully thought through. So, developers! Get audio designers involved from the start — and audio designers, be prepared for these challenges.

If I am presented with a list of sounds, then I will ask to play the game and develop my own list. This isn’t because I think I know better, but because audio is my profession, and implementing the various design considerations required can be a lot easier if you start from scratch.

That’s not at all to say you should thrown away the developers’ list. On the contrary, you should follow it — just don’t do so blindly. Plus techniques such as generative sound systems, combining assets, compression, etc, can not only sound better but also be critical to the audio design. These are often something developers would not consider requesting.

Why would they? It’s not their profession to know the ins and outs of iPhone audio design; it’s the audio designers. This can see composers and sound designers also having to act as directors, designers, and leads, and with most indie game developers operating as a small team. With one person doing audio, development on the iPhone can see the audio guy becoming a very diverse one man band.

And Other Considerations…

I’d like to return to user behavior — and how that can enable viral marketing. Viral marketing has been great for the iPhone; thanks to its mobile nature, easy web connectivity and small app price, stuff can really get around! Audio is one of the best indirect and direct ways to make others aware of what you’re playing — unlike visuals, you don’t have to be looking in any particular direction.

With existing brands this is easier, since most sound logos are an established part of the brand, making both the sound and the brand instantly recognizable.

Establishing a brand is one of the trickiest parts of starting a new product, and sound is key feature. With this in mind you can see how the audio starts to play a role outside of the game.

Genres of games on the iPhone have been incredibly diverse, with pretty much every existing base covered, as well as a lot of innovation. Games from other devices have been modified to work on the iPhone, games have been made just for the iPhone, and some games have been made with very little consideration for the device at all. Some work well and others don’t, but at the end of the day, with well over 50,000 games, the chances are it has been done. In terms of audio for games, well, they all have it — but few do it well.

All the same, the level of quality on most successful iPhone games has set the bar very high. This includes the audio, which obviously needs to match the high standards of the game. Although this can seem very tricky given the challenges being faced, it is by no means impossible — so get out there and make big audio for the next big game!(source:gamasutra


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