ffmpeg Libraries Documentation翻译

Libavutil Documentation

The libavutil library is a utility（有多种用途的） library to aid(帮助; 资助; 救助; 促进) portable（便携式） multimedia programming. It contains safe portable string functions, random number generators, data structures, additional mathematics（数学，算法） functions, cryptography（密码） and multimedia related functionality (like enumerations（枚举） for pixel and sample formats). It is not a library for code needed by both libavcodec and libavformat.
The goals for this library is to be:
Modular（模块化）
It should have few interdependencies（相互依存关系） and the possibility of disabling individual parts（禁用部分功能） during ./configure.
Small
Both sources and objects should be small.

Efficient（高效）
It should have low CPU and memory usage（使用）.

Useful
It should avoid useless features that almost no one needs.

Libswscale Documentation

The libswscale library performs highly optimized（优化） image scaling and colorspace(彩色空间，色隙) and pixel format conversion operations.

Specifically, this library performs the following conversions:

• Rescaling(尺度改变，改比例;): is the process of changing the video size. Several rescaling options and algorithms(算法) are available. This is usually a lossy（有损耗的，致损耗的） process.
• Pixel format conversion: is the process of converting the image format and colorspace(彩色空间，色隙) of the image, for example from planar YUV420P to RGB24 packed. It also handles packing conversion, that is converts from packed layout (all pixels belonging to distinct(不同的) planes（平面; 飞机） interleaved(交叉存取的，隔行扫描的) in the same buffer), to planar（平面的，平坦的） layout (all samples belonging to the same plane stored in a dedicated（专用的; 专注的） buffer or "plane").

  This is usually a lossy process in case the source and destination colorspaces differ.

Libswresample Documentation

The libswresample library performs highly optimized（优化） audio resampling（重采样）, rematrixing（重写矩阵） and sample format（样本格式） conversion operations.

Specifically, this library performs the following conversions:

• Resampling: is the process of changing the audio rate, for example from a high sample rate of 44100Hz to 8000Hz. Audio conversion from high to low sample rate is a lossy process（有损过程）. Several resampling options and algorithms(算法) are available.
• Format conversion: is the process of converting the type of samples, for example from 16-bit signed samples to unsigned 8-bit or float samples. It also handles packing conversion, when passing from packed layout (all samples belonging to distinct channels interleaved(交叉存取的，隔行扫描的) in the same buffer), to planar layout (all samples belonging to the same channel stored in a dedicated（专用的; 专注的） buffer or "plane").
• Rematrixing: is the process of changing the channel layout, for example from stereo（立体声） to mono（单声道的）. When the input channels cannot be mapped to the output streams, the process is lossy, since it involves（涉及） different gain(增进) factors（因素） and mixing.

Various other audio conversions (e.g. stretching and padding) are enabled through dedicated(专用的) options.

Libavcodec Documentation

The libavcodec library provides a generic encoding/decoding（编码/解码） framework and contains multiple decoders and encoders for audio, video and subtitle（字幕） streams, and several bitstream filters.

The shared architecture（总体、层次结构 ）provides various services ranging from bit stream I/O to DSP optimizations(优化), and makes it suitable for implementing robust（稳健） and fast codecs as well as for experimentation（实验）.

Libavformat Documentation

The libavformat library provides a generic framework for multiplexing（复用） and demultiplexing（解复用） (muxing（多路复用） and demuxing) audio, video and subtitle（字幕） streams. It encompasses（包括） multiple muxers and demuxers（分配器） for multimedia container formats.

It also supports several input and output protocols to access a media resource.

Libavdevice Documentation

The libavdevice library provides a generic framework for grabbing（抓） from and rendering to many common multimedia input/output devices, and supports several input and output devices, including Video4Linux2, VfW, DShow, and ALSA.

Libavfilter Documentation

The libavfilter library provides a generic audio/video filtering framework containing several filters, sources and sinks（水池，水槽）.（libavfilter库提供了一个通用的音频/视频滤波框架包含几个过滤器，源和池。）