A Codec is a device or program capable of performing encoding and decoding on a digital data stream or signal. The word codec may be a combination of any of the following: 'Compressor-Decompressor', 'Coder-Decoder', or 'Compression/Decompression algorithm'.
Codecs encode a stream or signal for transmission, storage or encryption and decode it for viewing or editing. Codecs are often used in videoconferencing and streaming media solutions. A video camera's ADC converts its analog signals into digital signals, which are then passed through a video compressor for digital transmission or storage. A receiving device then runs the signal through a video decompressor, then a DAC for analog display. A "codec" is a generic name for a video conferencing unit.
An audio compressor converts analog audio signals into digital signals for transmission or storage. A receiving device then converts the digital signals back to analog using an audio decompressor, for playback.
Most codecs are lossy, in order to get a reasonably small file size. There are lossless codecs as well, but for most purposes the almost imperceptible increase in quality is not worth the considerable increase in data size. The main exception is if the data will undergo more processing, especially editing, in the future, in which case the repeated lossy encoding could degrade the quality of the eventual file too much. Using more than one codec or encoding scheme throughout processing can also degrade quality but there are many situations where this cannot be avoided.
Many codecs are designed to emphasize certain aspects of the media to be encoded. For example, a digital video (using a DV codec) of a sports event, such as baseball or soccer, needs to encode motion well but not necessarily exact colors, while a video of an art exhibit needs to perform well encoding color and surface texture. There are hundreds or even thousands of codecs ranging from free ones to ones costing hundreds of dollars or more.
Many multimedia data streams need to contain both audio and video data, and often some form of metadata that permits synchronization of the audio and video. Each of these three streams may be handled by different programs, processes, or hardware; but for the multimedia data stream to be useful in stored or transmitted form, they must be encapsulated together in a container format.
While many people explain that AVI is a codec, they are incorrect. AVI (nowadays) is a container format, which many codecs might use (although not to ISO). There are other well known alternative containers such as Ogg, ASF, QuickTime, RealMedia and MP4.
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參考答案:Codec 是一个装置或者规划能够在一笔数传数据上的表演入码和解码法水流或信号。 字 codec 可能是一个任何下列各项的组合: 'Compressor-Decompressor' ， 'Coder - 破码器' 或 '压缩/减压运算法则'.
Codecs 对于传输，储藏或密码技术改为暗码水流或信号并且为看或编辑改为暗码译码它。 Codecs 时常被用于视讯会议和流媒体解决。 录像机的 ADC 把它的类比信号转换成数传信号,然后被为数传传输或储藏通过一个电视的压缩物。 一个收受装置然后经过电视的 decompressor 跑信号, 然后对于类比展览的 DAC。 " codec" 是一个视讯会议单位的一个总称的名字。
一个声音的压缩物对于传输或储藏进入数传信号之内转换类比声音信号。 一个收受装置然后把数传信号转换回使用声音的 decompressor 的类比,对于录灌再生。
大多数的 codecs 是耗损,为了要得到适度小的文件大小。 那里是无损失的 codecs 也, 要不是大多数的目的质量几乎不能感知的增加不是值数据大小的相当多的增加。 如果数据将会更遭受处理，主要的例外是, 尤其编辑,未来，在哪一情况改为暗码的重复耗损可以降低最后的文件质量人格太多。使用超过 codec 或到处改为暗码方案处理也能降低质量人格但是有这不能够被避免的许多情形。
许多 codecs 被设计强调媒体的特定方面被改为暗码。 举例来说，像棒球或足球这样的运动比赛的数传录象机 (使用 DV codec), 需要把运动改为暗码得很好但不是必然精确的颜色而艺术的录象机展现需要很好地运行入码颜色和表面质地。 那里是数百或从自由的一些到元或更多的一些成本计算数百排列的平坦数以千计 codecs。
许多多媒体数据水流需要包含声音和电视的数据, 和时常一些形式的允许声音的和电视者的同步 metadata。 每一条这三条水流可能被不同计画，程序或硬件处理;如果多媒体数据以储存或传输形式流出是有用的,他们一定在一个容器格式中被一起装入胶囊。
许多人解释， AVI 是 codec ，不过他们是不正确的。 AVI(现在) 是一个容器格式, 许多 codecs 可能使用。 ( 虽然不到国际标准组织) 另外地有广为人知的其它可能的容器 , 像是 Ogg ， ASF ， QuickTime ， RealMedia 和 MP4。
貌似这里可以解决该问题:
