标题：TV Tuner
[edit] Variants
A DVB-S2 tuner card
D-Link external TV tuner
TV tuners are available in a number of different interfaces: as PCIbusexpansion card, PCI Express (PCIe) bus, PCMCIA, Mini PCI Express, PCMCIA Express or USB devices also exist (hdhomerun) and (HAVA). In addition, some video cards double as TV tuners, notably the ATI All-In-Wonder series. The card contains a tuner and an analog-to-digital converter (collectively known as the analog front end) along with demodulation and interface logic. Some very cheap cards lack an onboard processor and, like a Winmodem, rely on the system's CPU for demodulation.
There are currently four kinds of tuner card on the market:[edit] Analog TV tunersCheaper analog television cards output a raw video stream, suitable for real-time viewing but ideally requiring some sort of compression if it is to be recorded. More expensive models encode the signal to Motion JPEG or MPEG, relieving the main CPU of this load. Many cards also have analog input (composite video or S-Video) and many also provide FM radio reception.[edit] Digital TV tunersDigital TV is broadcast as an MPEG-2 stream, so no encoder is necessary; instead, the digital cards either provide the whole MPEG transport stream or extract the individual (audio and video) elementary streams.[edit] Hybrid tunersA hybrid tuner has one tuner that can be configured to act as an analog tuner or a digital tuner. Switching in between the systems is fairly easy, but cannot be done immediately. The card operates as a digital tuner or an analog tuner until reconfigured.[edit] Combo tunersThis is similar to a hybrid tuner, except there are two separate tuners on the card. One can watch analog while recording digital, or vice versa. The card operates as an analog tuner and a digital tuner simultaneously. The advantages over two separate cards are cost and utilization of expansion slots in the computer. As many regions around the world convert from analog to digital broadcasts, these tuners are gaining popularity.
Like the analog cards, the Hybrid and Combo tuners can have specialized chips on the tuner card to perform the encoding, or leave this task to the CPU. The tuner cards with this 'hardware encoding' are generally thought of as being higher quality. Small USB tuner sticks have become more popular in 2006 and 2007 and are expected to increase in popularity. These small tuners generally do not have hardware encoding due to size and heat constraints.
While most TV tuners are limited to the radio frequencies and videoformats used in the country of sale, many TV tuners used in computers use DSP, so a firmware upgrade is often all that's necessary to change the supported video format. Many newer TV tuners have flash memory big enough to hold the firmwares for decoding several different video formats, making it possible to use the tuner in many countries without having to flash the firmware. However, while it is generally possible to flash a card from one analog format to another due to the similarities, it is generally not possible to flash a card from one digital format to another due to differences in decode logic necessary.
Many TV tuners can function as FM radios; this is because there are similarities between broadcast television and FM radio. The FM radio spectrum is close to (or even inside) that used by VHF terrestrial TV broadcasts. And many broadcast television systems around the world use FM audio. So listening to an FM radio station is simply a case of configuring existing hardware.[edit] Mobile TVExternal TV tuner card attachments are available for mobile phonehandsets like the iPhone, for watching mobile TV, via TV stations on 1seg in Japan (SoftBank), and for soon for the proprietary subscription-based MediaFLO in the U.S. (Qualcomm). There is also a "converter" for watching DVB-H in Europe and elsewhere via WiFistreaming video (PacketVideo).
[edit] Video capture
Video capture cards are a class of video capture devices designed to plug directly into expansion slots in personal computers and servers. Models from many manufacturers are available; all comply with one of the popular host bus standards including PCI, newer PCI Express (PCIe) or AGP bus interfaces.
These cards typically include one or more software drivers to expose the cards' features, via various operating systems, to software applications that further process the video for specific purposes. As a class, the cards are used to capture baseband analog composite video, S-Video, and, in models equipped with tuners, RF modulated video. Some specialized cards support digital video via digital video delivery standards including Serial Digital Interface (SDI) and, more recently, the emerging HDMI standard. These models often support both standard definition (SD) and high definition (HD) variants.
While most PCI and PCI-Express capture devices are dedicated to that purpose, AGP capture devices are usually included with the graphics adapted on the board as an all-in-one package. Unlike video editing cards, these cards tend to not have dedicated hardware for processing video beyond the analog-to-digital conversion. Most, but not all, video capture cards also support one or more channels of audio.
There are many applications for video capture cards including converting a live analog source into some type of analog or digital media, (such as a VHS tape to a DVD), archiving, video editing, scheduled recording (such as a DVR), television tuning, or video surveillance. The cards may have significantly different designs to optimally support each of these functions.
One of the most popular applications for video capture cards is to capture video and audio for live Internet video streaming. The live stream can also be simultaneously archived and formatted for video on demand. The capture cards used for this purpose are typically purchased, installed, and configured in host PC systems by hobbyists or systems integrators. Some care is required to select suitable host systems for video encoding, particularly HD applications which are more affected by CPU performance, number of CPU cores, and certain motherboard characteristics that heavily influence capture performance.
电视调谐器电视调谐卡 
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Hauppauge的天盛传媒电视调谐卡 
电视调谐器卡是计算机元件 ，使电视信号由计算机接收。 大多数电视调谐器也可作为视频采集卡，让他们记录到一个硬盘上的电视节目。 
1变种1.1模拟电视tuners1.2数字电视tuners1.3混合tuners1.4组合tuners1.5手机2台视频capture3参见
变体阿的DVB - S2调谐器卡 
友讯外部电视调谐器 
电视调谐器，可在不同接口数目：作为的PCI总线扩展卡的PCI Express（PCIe）总线， 的PCMCIA，迷你的PCI Express，Express或的PCMCIA 的USB设备还存在（hdhomerun）和（HAVA的）。 此外，诸如电视调谐器双某些视频卡，特别是ATI的全功能的一系列奇迹。 本卡片包括调谐器和一个模拟数字转换器（统称为模拟前端）以及解调和接口逻辑。 有些很便宜卡缺乏对系统的解调的CPU处理器和片上，像一个Winmodem，依赖。 
目前有4种调谐器卡在市场上：模拟电视调谐器廉价的模拟电视卡的视频输出原始视频流，实时观看合适的，但需要一些理想的压缩类型，如果它要被记录下来。 价格昂贵的机型编码信号的Motion JPEG或的MPEG，减轻了主CPU的这个包袱。 也有很多卡模拟输入（ 复合视频或S -视频 ）和许多还提供FM调频收音机。数字电视调谐器数字电视是广播作为的MPEG - 2流，因此没有编码器是必要的，相反，数码卡可以提供整个MPEG传输流或提取个人（音频和视频）基本流。混合调谐器一种混合调谐器有一个调谐器，可以配置作为一个模拟调谐器或数字调谐器。 切换系统之间的相当容易，但不能立即进行。 该卡不仅可作为数字调谐器或直到重新配置模拟调谐器。组合调谐器这类似于一种混合调谐器，除了有两个卡上的单独的调谐器。 人们可以观看模拟数字录音时，反之亦然。 该卡的运作，作为模拟调谐器和一个数字调谐器同时进行。 在两个单独的卡的优点是成本和电脑的扩展槽利用。 由于世界许多地区，从模拟信号转换成数字广播，这些调谐器的日益普及。 
像模拟卡，混合和Combo调谐器可以对调谐器卡专用芯片来执行编码，或把这一任务交给了CPU。 这一'硬件编码'的电视卡一般被认为是质量更高。 小型USB调谐器棒越来越普遍，在2006年和2007年预计将增长受欢迎。 这些小型调谐器一般不具备硬件编码，由于规模和热限制。 
虽然大多数电视调谐器只限于无线电频率，在销售国使用的视频格式，很多电视调谐器在使用电脑中使用数字信号处理器 ，所以固件升级往往是所有的必要改变支持的视频格式。 许多较新的电视调谐器的快闪记忆体足够大举行解码多种不同的视频格式的固件，使得有可能使用在许多国家，而不必闪存固件调谐器。 但是，一般可以从一个模拟闪存卡格式，到另一个相似之处到期，一般不可能从一个数字闪存卡格式，另一个在解码逻辑差异等必要的。 
许多电视调谐器可作为调频收音机，这是因为存在着广播电视和调频广播相似之处。 调频无线电频谱接近（甚至内），通过甚高频地面电视广播使用。 和许多世界各地的广播使用调频音频电视系统。 因此，收听调频广播电台，是一个简单的配置现有的硬件情况。移动电视外部电视调谐卡附件可用于像iPhone手机手机，移动电视的收看，通过电视台在日本的单波段（ 软银 ），以及为即将专有订阅为基础的美国（ 高通）MediaFLO的 。 还有一个“转换器”的收看DVB - H标准在欧洲，并通过无线视频流（PacketVideo的）其他地方。
视频捕捉视频采集卡的视频采集，旨在插入个人电脑和服务器的扩展槽直接设备类。 许多厂商的产品提供，所有符合流行的主机总线标准，包括PCI，新的PCI Express（PCIe）或牙周炎总线接口之一。 
这些卡通常包括一个或多个软件驱动程序，揭露卡的特点，通过各种操作系统，应用软件的进一步进程的用于特定目的的视频。 作为一个阶级，该卡是用来捕获基带模拟复合视频，S -视频，并与调谐器设备，射频调制视频模式。 一些专门的卡支持通过数字视频传输标准，包括串行数字接口（SDI），以及最近，新兴的HDMI标准的数字视频。 这些模型往往同时支持标准清晰度（SD）和高清晰度（HD）的变种。 
虽然大多数的PCI和PCI - Express捕获设备专门为此目的，AGP接口捕获设备通常包含在董事会调整为所有的图形功能于一身的包。 与视频编辑卡，这些卡往往没有处理超出了对模数转换视频的专用硬件。 大多数但不是全部，视频采集卡还支持音频一个或多个频道。 
有视频采集卡，其中包括一些转换成模拟或数字媒体类型的现场模拟信号源（如录影带磁带一影碟 ），归档许多应用，视频编辑，预定的录制（如硬盘录像机 ），电视调谐或视频监控。 该卡可能有显着不同的设计能有效地支持这些函数。 
对视频采集卡最流行的应用之一就是捕捉视频和实时网络视频流媒体音频。 直播流也可以同时存档和视频点播格式。 捕捉用于这一目的的卡是典型的购买，安装，并在主机电脑系统配置的业余爱好者或系统集成商。 在一些护理需要选择合适的视频编码的主机系统，特别是房屋较为受的CPU性能，CPU核心数量的应用程序，和某些主板特点，严重影响到捕获性能。