Closed Captioning for 流媒体

大型网络广播公司也应该关注最近全国聋人协会(NAD)起诉Netflix的一项裁决, 其中NAD声称，《百家乐软件app最新版下载》规定Netflix有义务为其“即时观看”网站加上标题. In rejecting Netflix’s motion to dismiss, 法院裁定，互联网是一个“公共场所”，因此受该法案的约束. Netflix later settled the lawsuit, 同意在3年内为所有内容加上标题，并支付约800美元,000 for NAD’s legal fees and other costs. In the blog post referenced previously, the attorney stated: “[P]roviding captioning earlier, 而不是后来, 这应该是任何视频节目所有者的目标，因为这可能是大多数分销商的交付要求, 无论如何, may serve to avoid potential ADA claims.” This sounds like good advice for any significant publisher of web-based video.

自愿Captioners

Beyond those who must caption, 越来越多的组织为听力受损的观众提供字幕, to help monetize their video, 或两个. One company big into caption-related monetization is Boston-based RAMP. I spoke briefly with Nate Treloar, the company’s VP of strategic partnerships.

简而言之, 与此相关的是，标题提供了元数据，可以为增强搜索引擎优化(SEO)的发布过程提供数据。, such as topic pages and microsites, that are impossible without captions. RAMP was originally created to produce such metadata for its clients, 直到它的许多电视客户发现, 包括CNBC, 福克斯商业, 康卡斯特SportsNet, 和高尔夫频道, would soon have to have captioning on the web.

图3. RAMP’s cloud-based captioning and metadata creation workflow

如图所示 图3, RAMP’s technology can input closed captions from text or convert them from audio, 使用专利算法，优先考虑驱动大多数文本搜索的名词的准确性. 该内容经过处理并转换为时间编码的文本和标记，以便在SEO中使用动态缩略图，用于视频搜索等应用程序. The transcripts can then be edited for use in web captioning.

RAMP’s prices depend upon volume commitment and the precise services performed, 但特洛尔表示，视频处理的成本从每分钟几美分到几美元不等. With customers such as FOX 新闻 reporting a 129% growth in SEO traffic, 对于视频在网站整体内容中占据相当大比重的网站来说，这笔投资似乎是值得的.

Now that we know who’s captioning for the web, let’s explore how it’s done.

Creating Closed Captions for Streaming Video

There are two elements to creating captions: The first involves creating the text itself; the second involves matching the text to the video. 在我们进入两者的细节之前，让我们回顾一下广播电视的字幕是如何工作的.

在美国.S., TV captioning became required under the Television Decoder Circuitry Act of 1990, which prompted the Electronics Industry Association to create EIA-608, 它现在被称为CEA-608，是继EIA之后的消费电子协会的缩写. 短暂的, Section 608 captions are limited to 60 characters per second, 使用一个基于拉丁的字符集，只能用于有限的语言集. 这些轨道嵌入到模拟广播的第21行数据区(也称为垂直消隐间隔)。, so they are retrieved and decoded along with the audio/video content.

其中CEA-608用于模拟广播，CEA-708(以前的EIA-708)用于数字广播. CEA-708规范更加灵活，可以支持具有多种字体的Unicode字符, 大小, 颜色, 和风格. CEA-708字幕作为文本轨道嵌入到携带视频的传输流中, which is typically MPEG-2 or MPEG-4.

A couple of key points here. 第一个, if you’re converting analog or digital TV broadcasts, it’s likely that the text track is already contained therein, so the caption creation task is done. 大多数企业编码工具在将视频转码分发到OTT或其他可以识别和播放嵌入文本轨道的设备时，都可以通过该文本轨道.

不幸的是, though QuickTime and iOS players can recognize and play these embedded text tracks, 其他格式, 比如Flash, 光滑的流, 和HTML5, 不能. So to create captioning for these 其他格式, 您需要从广播提要中提取标题文件，并将其格式化为多种基于标题的格式(稍后将详细讨论这些格式). Not all enterprise encoders can do this today, 虽然这是一个关键的功能，大多数产品应该在不久的将来支持.

Captioning Your Live Event

如果您不从广播输入开始，则必须自己创建字幕. 对于现场活动, Step 1 is to find a professional captioning company such as CaptionMax, 自1993年以来，哪家公司一直为现场和点播演讲提供字幕服务. I spoke with COO Gerald Freda, who described this live event workflow.

与CaptionMax, 你签约一名现场速记员(又名实时字幕员)，他通常不在现场，通过电话或流媒体连接接收音频馈送. The steno machine has 22 keys representing phonetic parts of words and phrases, rather than 60-plus keys on a typical computer keyboard. The input feeds through software, which converts it to text. This text is typically sent to an IP address in real time, where it’s formatted as necessary for the broadcast and transmitted in real time. 文本以编程方式与视频播放器链接，并在侧车窗口或, 最好是, atop the streaming video just like TV.

Unlike captions for 随需应变 videos, 没有尝试将文本与口语同步-文本在可用的情况下立即呈现. If you’ve ever watched captioning of a live broadcast, you’ll notice that this is how it’s done on television, and there’s usually a lag of 2–4 seconds between the spoken word and the caption.

According to Phil McLaughlin, president of EEG Enterprises, Inc., 流媒体文本呈现方式的微小变化可能会影响字幕是否符合规定其使用的各种法规的要求. 顺便说一下背景, EEG was one of the original manufacturers of “encoders” that multiplex analog and digital broadcasts with the closed caption text; it currently manufactures a range of web and broadcast-related caption products. The company also has a web-based service for captioning live events.

Here are some of the potential issues McLaughlin was referring to. 顺便说一下背景, 请注意，听证会上有关FCC规定电视广播公司必须配字幕的措辞讨论了提供“相当于电视字幕体验的配字幕体验”.McLaughlin怀疑在sidecar中呈现字幕是否符合这一等效要求，因为观众必须在sidecar和视频之间切换, which is much harder than watching the text over the video. 在NAB 2012, McLaughlin的公司演示了如何使用行业标准组件在Flash Player上提供实时字幕, 因此，到2013年3月，广播公司必须为现场直播配字幕时，挎斗可能已经成为历史.

Closed Captioning in Wowza Media Server 3.5

标题转换的引入通过最小化所需源文件的数量来简化部署, though the process is slightly different for live vs. 随需应变

2012年11月27日