20.6 了解视频格式——REAPER用户手册中文版

琴韵晓波

楼主 琴韵晓波说：
20.6 Understanding Video Formats
20.6 了解视频格式

Newcomers to video often find the whole topic bewildering. This section aims to guide you thru some basic concepts, so that you can at least confidently get started. It is not comprehensive and by no means covers everything that you should eventually need to know.
刚开始接触视频的人常常觉得整个话题令人费解。本节旨在引导您了解一些基本概念,以便您至少可以自信地开始学习。它并不全面,也绝不涵盖你最终需要知道的一切。
Video files hold video and other data that exhibits a number of attributes such as frame rate, pixel dimensions and audio channels. Different formats can be used for capturing, saving, editing and distribution of this data. Different formats are characterised by the whichever video container and codec they use.
视频文件,保存视频和其他数据,这些数据显示了许多属性,如帧率、像素尺寸和音频通道。可以使用不同的格式来捕获、保存、编辑和分发该数据。不同格式的特征在于它们使用的视频容器和编解码器。
Video signal attributes
视频信号属性
As with most things audio and video, the higher the numbers the better the quality and the larger the resulting file size! In particular, video characteristics include:
与大多数音频和视频一样,数字化越高,质量越好,产生的文件大小也越大!特别是,视频特征包括:
● Frame size: the video frame's dimensions, measured in pixels, typically within the range 160 (width) by 120 (height) to 1920 by 1080 (Full HD).
●帧大小: 视频帧的尺寸,以像素为单位,通常在160(宽)乘120(高)到1920乘1080(全高清)的范围内。
● Frame rate: the speed with which each frame is first captured then played back. Each frame holds a still image. The human eye starts to see motion (albeit “jerky”) at 8 frames per second (fps). The motion will start to appear smooth at rates of 24 fps and above. The U.S. standard frame rate for 720 HD (1280 by 720 pixels) is 59.94 fps, often rounded up to 60 fps
●帧率: 每帧先被捕获然后被回放的速度。每一帧包含一幅静止的图像。人眼以每秒8帧(Fps)的速率开始,就能看到“断断续续的”运动。在24fps或更高的速率下,该运动将开始显得流畅。720高清(1280 x 720像素)的美国标准帧率为59.94帧/秒,通常四舍五入为60帧/秒。
● Aspect ratio:the ratio of width to height. This can be expressed either as whole numbers, e.g. 16 by 9, or as a decimal ratio, e.g. 1.78:1. 16 by 9 is the ratio used by widescreen TV.
●宽高比: 宽度与高度的比例。这既可以表示为整数,例如16乘以9,也可以表示为小数比,例如1.78:1。16乘9是宽屏电视使用的比率。
● Bit rate: the data transfer rate, i.e. from the file to the screen. Bit rate is usually measured in megabits per second (mps). By way of example, HD Blu-ray video typically uses a bit rate of 20 mbps, standard DVD quality is around 6 mbps. HD mobile phone, on the other hand uses rates of 2500 (HD) or 5000 (Full HD) kilobits per second (kbps).
●比特率: 数据传输速率,即从文件到屏幕的传输速率。比特率通常以兆比特每秒(mps)为单位进行测量。例如,HD蓝光视频通常使用20mbps的比特率,标准DVD质量约为6mbps。另一方面,高清移动电话使用2500(高清)或5000(全高清)千比特每秒(kbps)的速率。
● Audio sample rate: the number of samples per second used to digitize recorded sound. This is discussed in Chapter 2 and Chapter 3.
●音频采样率: 用于录制数字化声音时,每秒的采样数。这在第二章和第三章中已讨论。
Container files
容器文件
Container files are files that contain video (and other related) data. You are probably at least vaguely familiar with commonly used container extensions such as .MOV, and AVI. Different containers provide different degrees of support for (for examples) different video and audio compression formats, subtitles, and so on. For example, several container formats support multiple audio streams, others support only one. In fact, you can learn very little about a video file from its container type alone. To do that, right-click over the video item within REAPER and choose Video Item Properties... from the context menu. An example is shown above.
容器文件是包含视频(和其他相关)数据的文件。您可能至少对常用的容器扩展名(如.MOV和AVI)有所了解。不同的容器提供不同程度的支持(例如)不同的视频和音频压缩格式、字幕等。例如,少数容器格式支持多个音频流,而其他格式仅支持一种。事实上,仅从视频文件的容器类型可以了解到的信息很少。要执行此操作,请右键单击REAPER中的视频对象,然后从上下文菜单中选择“媒体源属性...”。上面显示了一个示例。
When rendering video in REAPER (see Chapter 21) available formats are AVI, QT/MOV/MP4, MKV and WEBM.
在REAPER中渲染视频时(见第21章),可用的格式有AVI、QT/MOV/MP4、MKV和WEBM。
Codecs
编解码器
If the container format provides a container for holding a file's data, then the codec (coder/decoder) is the method by which that data is actually encoded. The very large number of codecs available makes this whole topic something of a minefield. Important characteristics of codecs include their video quality, performance factors (such as compression/decompression speed, supported profiles, options, supported resolution, and so on). Some codecs are available free of charge, others you have to pay for. Because raw video files are so large, file size compression is one of the most important aspect of video codecs. Indeed, most consumer standard recording equipment captures video in the first place in compressed rather than raw video format.
如果容器格式提供了一个用于保存文件数据的容器,那么编解码器(编码器/解码器)就是对数据进行实际编码的方法。可用的编解码器非常多,使整个主题成为雷区。编解码器的重要特性包括其视频质量、性能因素(如压缩/解压缩速度、支持的配置文件、选项、支持的分辨率等)。有些编解码器是免费的,有些则需要付费。由于原始视频文件太大,文件大小压缩是视频编解码器最重要的方面之一。事实上,大多数消费者标准录制设备,首先捕获的是压缩的视频格式,而不是原始的视频格式。
When rendering in REAPER, your choice of codec will largely depend on which container format is selected.
在REAPER中渲染时,编解码器的选择在很大程度上取决于所选的容器格式。
Note: For more technical information, see:
注: 有关此主题的更多详细技术信息,请参阅:
https://forum.cockos.com/showthread.php?t=82459

琴韵晓波

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