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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,114 +1,114 @@ | ||
| # FFmpeg | ||
|
|
||
| ## 概念 | ||
|
|
||
| ### Muxing/Demuxing | ||
|
|
||
| IO Muxing/Demuxing library， Mux是multiplex的缩写，是多路传输 | ||
| Muxing就是动词，混流，将视频流，音频流，字幕流混合到一个文件中 | ||
| Demuxing是分离解析，从一个文件中分离音频或视频 | ||
|
|
||
| 合成器Synthesizer | ||
| 所谓的“合成”把音频，视频流等用一个容器文件Contaienr封装起来，播放时先调用分离器Splitter分别获取 | ||
| 需要解码的流数据。 | ||
| 滤镜Filter实际就是指各种分离器或解码器(视频解码器和音频解码器)的统称 | ||
|
|
||
| ### Codec | ||
|
|
||
| 执行编码的软件叫做编码器Coder或Encoder | ||
| 执行解码的软件叫做解码器Decoder | ||
| 编码器与解码器合称为编解码器Codec | ||
|
|
||
| ### lib | ||
|
|
||
| ffmpeg是依赖file system，而libavXXX是通用的库，可以在内存中进行处理 | ||
|
|
||
| - avutil， 工具库，包括安全的字符串函数，随机数等 | ||
| - avcodec， 一个通用的编解码框架，包含了多种用于音频流，视频流，字幕流等编解码器， | ||
| 和比特流过滤器filter | ||
| - avformat， 一个通用多路复用multiplexing/muxing与反多路复用demultiplexing/demuxing框架， | ||
| 包含多种复用器muxer和解复用器demuxer | ||
| - avdevice，一个通用框架库，从多媒体设备上抓取流媒体，或渲染至多媒体 | ||
| - avfilter，通用filtering库 | ||
| - swscale，提供高度优化的图像缩放，颜色空间与像素格式 | ||
| - swresample，音频重采样 | ||
|
|
||
| ### 解码流程 | ||
|
|
||
|  | ||
|
|
||
| - AVFormatContext 容器，默认使用avformat_alloc_context()初始化 | ||
| - AVIOContext 字节流，默认使用avio_alloc_context()初始化 | ||
| - AVStream 流 | ||
| - AVPacket 包 | ||
| - AVCodec 编码，压缩过程 | ||
| - AVFrame 帧数据，未压缩的数据， 必须使用av_frame_alloc()和av_frame_free()来管理，具体的数据还需 | ||
| 额外的操作 | ||
|
|
||
| ## 命令行 | ||
|
|
||
| ### images2video | ||
|
|
||
| ```cmd | ||
| ffmpeg.exe -r 60 -f image2 -s 1420x944 -i test/%07d.png -vcodec libx264 -crf 25 -pix_fmt yuv420p test2.mp4 | ||
| -r 帧率，每秒读取图片的数量 | ||
| -f | ||
| -s 分辨率 | ||
| -i | ||
| -crf | ||
| -pix_fmt | ||
| ``` | ||
|
|
||
| ## Java | ||
|
|
||
| ### JavaCPP Presents FFmpeg | ||
|
|
||
| JavaCPP是一个开源库，提供了Java高效访问本地C++的方法，采用JNI技术实现，支持所有Java | ||
|
|
||
| 为调用本地的方法，JavaCPP生成对应的JNI代码，且把这些代码输入到C++编译器，用来构建本地库， | ||
| 使用Java的Annotations特性在运行时自动调用Loader.load()方法从Java资源中直接获取。 | ||
|
|
||
|
|
||
| ### Xuggle | ||
|
|
||
| Java封装的FFmpeg库， 目前代码已经deprecated啦！ | ||
|
|
||
| - 要使用前端获取图片在后台生成视频再返回给前端的逻辑 | ||
|
|
||
| #### Xuggle概念 | ||
|
|
||
| 通过IMediaWriter完成由图片生成视频文件的逻辑 | ||
|
|
||
| ```java | ||
|
|
||
| final int MIN_BITRATE = 2000000; | ||
| final double BPP = 1; | ||
|
|
||
| int bitRate = (int)Math.max(w * h * fps * BPP, MIN_BITRATE); | ||
| IRational frameRate = IRational.make(fps, 1); | ||
| deltat = 1e6 / frameRate.getDouble(); | ||
|
|
||
| IMediaWriter mediaWriter = ToolFactory.makeWriter(path); | ||
| mediaWriter.addVideoStream(0, 0, ICodec.ID.CODEC_ID_MPEG4, w, h); | ||
|
|
||
| IPixelFormat.Type pixFmt = IPixelFormat.Type.YUV420P; | ||
| IConverter converter = ConverterFactory.createConverter(ConverterFactory.XUGGLER_BGR_24, pixFmt, w, h); | ||
|
|
||
| IContainer container = mediaWriter.getContainer(); | ||
| IStreamCoder coder = container.getStream(0).getStreamCoder(); | ||
| coder.setBitRate(bitRate); | ||
| // .... | ||
| IMetaData meta = container.getMetaData(); | ||
| meta.setValue("title", "meijie-video"); | ||
| // .... | ||
|
|
||
| IVideoPicture frame = this.converter.toPicture(image, (long)(this.frameNo * this.deltat)); | ||
| frame.setQuality(0); | ||
| mediaWriter.encodeVideo(0, frame); | ||
|
|
||
| ``` | ||
|
|
||
| [1] https://www.ibm.com/developerworks/cn/java/j-lo-cpp/ | ||
| [2] https://protogalaxy.me/ffmpeg%e4%b8%8e%e5%85%b6javacpp%e5%ae%9e%e7%8e%b0%e8%b8%a9%e5%9d%91%e7%ba%aa%e5%bd%95/ | ||
| # FFmpeg | ||
|
|
||
| ## 概念 | ||
|
|
||
| ### Muxing/Demuxing | ||
|
|
||
| IO Muxing/Demuxing library， Mux是multiplex的缩写，是多路传输 | ||
| Muxing就是动词，混流，将视频流，音频流，字幕流混合到一个文件中 | ||
| Demuxing是分离解析，从一个文件中分离音频或视频 | ||
|
|
||
| 合成器Synthesizer | ||
| 所谓的“合成”把音频，视频流等用一个容器文件Contaienr封装起来，播放时先调用分离器Splitter分别获取 | ||
| 需要解码的流数据。 | ||
| 滤镜Filter实际就是指各种分离器或解码器(视频解码器和音频解码器)的统称 | ||
|
|
||
| ### Codec | ||
|
|
||
| 执行编码的软件叫做编码器Coder或Encoder | ||
| 执行解码的软件叫做解码器Decoder | ||
| 编码器与解码器合称为编解码器Codec | ||
|
|
||
| ### lib | ||
|
|
||
| ffmpeg是依赖file system，而libavXXX是通用的库，可以在内存中进行处理 | ||
|
|
||
| - avutil， 工具库，包括安全的字符串函数，随机数等 | ||
| - avcodec， 一个通用的编解码框架，包含了多种用于音频流，视频流，字幕流等编解码器， | ||
| 和比特流过滤器filter | ||
| - avformat， 一个通用多路复用multiplexing/muxing与反多路复用demultiplexing/demuxing框架， | ||
| 包含多种复用器muxer和解复用器demuxer | ||
| - avdevice，一个通用框架库，从多媒体设备上抓取流媒体，或渲染至多媒体 | ||
| - avfilter，通用filtering库 | ||
| - swscale，提供高度优化的图像缩放，颜色空间与像素格式 | ||
| - swresample，音频重采样 | ||
|
|
||
| ### 解码流程 | ||
|
|
||
|  | ||
|
|
||
| - AVFormatContext 容器，默认使用avformat_alloc_context()初始化 | ||
| - AVIOContext 字节流，默认使用avio_alloc_context()初始化 | ||
| - AVStream 流 | ||
| - AVPacket 包 | ||
| - AVCodec 编码，压缩过程 | ||
| - AVFrame 帧数据，未压缩的数据， 必须使用av_frame_alloc()和av_frame_free()来管理，具体的数据还需 | ||
| 额外的操作 | ||
|
|
||
| ## 命令行 | ||
|
|
||
| ### images2video | ||
|
|
||
| ```cmd | ||
| ffmpeg.exe -r 60 -f image2 -s 1420x944 -i test/%07d.png -vcodec libx264 -crf 25 -pix_fmt yuv420p test2.mp4 | ||
| -r 帧率，每秒读取图片的数量 | ||
| -f | ||
| -s 分辨率 | ||
| -i | ||
| -crf | ||
| -pix_fmt | ||
| ``` | ||
|
|
||
| ## Java | ||
|
|
||
| ### JavaCPP Presents FFmpeg | ||
|
|
||
| JavaCPP是一个开源库，提供了Java高效访问本地C++的方法，采用JNI技术实现，支持所有Java | ||
|
|
||
| 为调用本地的方法，JavaCPP生成对应的JNI代码，且把这些代码输入到C++编译器，用来构建本地库， | ||
| 使用Java的Annotations特性在运行时自动调用Loader.load()方法从Java资源中直接获取。 | ||
|
|
||
|
|
||
| ### Xuggle | ||
|
|
||
| Java封装的FFmpeg库， 目前代码已经deprecated啦！ | ||
|
|
||
| - 要使用前端获取图片在后台生成视频再返回给前端的逻辑 | ||
|
|
||
| #### Xuggle概念 | ||
|
|
||
| 通过IMediaWriter完成由图片生成视频文件的逻辑 | ||
|
|
||
| ```java | ||
|
|
||
| final int MIN_BITRATE = 2000000; | ||
| final double BPP = 1; | ||
|
|
||
| int bitRate = (int)Math.max(w * h * fps * BPP, MIN_BITRATE); | ||
| IRational frameRate = IRational.make(fps, 1); | ||
| deltat = 1e6 / frameRate.getDouble(); | ||
|
|
||
| IMediaWriter mediaWriter = ToolFactory.makeWriter(path); | ||
| mediaWriter.addVideoStream(0, 0, ICodec.ID.CODEC_ID_MPEG4, w, h); | ||
|
|
||
| IPixelFormat.Type pixFmt = IPixelFormat.Type.YUV420P; | ||
| IConverter converter = ConverterFactory.createConverter(ConverterFactory.XUGGLER_BGR_24, pixFmt, w, h); | ||
|
|
||
| IContainer container = mediaWriter.getContainer(); | ||
| IStreamCoder coder = container.getStream(0).getStreamCoder(); | ||
| coder.setBitRate(bitRate); | ||
| // .... | ||
| IMetaData meta = container.getMetaData(); | ||
| meta.setValue("title", "meijie-video"); | ||
| // .... | ||
|
|
||
| IVideoPicture frame = this.converter.toPicture(image, (long)(this.frameNo * this.deltat)); | ||
| frame.setQuality(0); | ||
| mediaWriter.encodeVideo(0, frame); | ||
|
|
||
| ``` | ||
|
|
||
| [1] https://www.ibm.com/developerworks/cn/java/j-lo-cpp/ | ||
| [2] https://protogalaxy.me/ffmpeg%e4%b8%8e%e5%85%b6javacpp%e5%ae%9e%e7%8e%b0%e8%b8%a9%e5%9d%91%e7%ba%aa%e5%bd%95/ | ||
| [3] https://github.com/leandromoreira/ffmpeg-libav-tutorial |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,61 +1,61 @@ | ||
| # bit technical | ||
|
|
||
| 有关位运算的知识，二进制表示的数字值 | ||
|
|
||
| ## 正负数 | ||
|
|
||
| 为表示正负数，使用了二进制补码机制，最高位为符号位，以一个字节为例： | ||
|
|
||
| ```c | ||
| 0000 0011 // +3 | ||
| 1000 0011 // -3 需要进行补码处理，如果不进行补码处理，就存在两个0：-0和+0 | ||
| // 编码先减一再取反，符号位不变 -> 1000 0010 -> 1111 1101 | ||
| // 解码先取反再加一，符号位不变 -> 1000 0010 -> 1000 0011 | ||
| ``` | ||
|
|
||
| ### 运算符 | ||
| - 取反 ~(1001 0010)=(0110 1101) | ||
| - 与 (1001 0011)&(0011 1101)=(0001 0001) | ||
| - 位或 (1001 0011)|(0011 1101)=(1011 1111) | ||
| - 位异或 (1001 0011)^(0011 1101)=(1010 1110) | ||
| - 左移 | ||
| - 无符号数 (0000 0011)<<2=(0000 1100) | ||
| - 有符号数 (0010 0011)<<2=(1000 1100),由正数变成负数 | ||
| - 右移 | ||
| - 无符号数(0000 1100)>>2=(0000 0011) | ||
| - 有符号数 | ||
| - 算术右移(1000 1010)>>2=(1110 0010)，左端以1填充 | ||
| - 逻辑右移(1000 1010)>>2=(0010 0010)，左端以0填充 | ||
|
|
||
| ### 表示集合 | ||
|
|
||
| 这里以int为32位为例，表示有32个元素的集合 | ||
|
|
||
| ```c | ||
| // A=1011,则集合位{0,1,3} | ||
| // A, B | ||
| #define ALL_BITS 0xffff | ||
| A|B // 集合的并 | ||
| A&B // 集合的交 | ||
| A&~B // 集合的差A-B | ||
| ALL_BITS^A // A的补集 | ||
| A|=1<<bit // 添加特定元素 | ||
| A^=1<<bit // 清除特定元素 | ||
| A&=1<<bit // 取特定元素 | ||
| A&(1<<bit)==0 // 判断是否存在 | ||
| ``` | ||
| ## 实例 | ||
| ### 判断一个数为2的N次方 | ||
| ```c | ||
| bool isPowOfTwo(int n){ | ||
| return 0 == (n & (n-1)); | ||
| } | ||
| ``` | ||
|
|
||
|
|
||
|
|
||
| # bit technical | ||
|
|
||
| 有关位运算的知识，二进制表示的数字值 | ||
|
|
||
| ## 正负数 | ||
|
|
||
| 为表示正负数，使用了二进制补码机制，最高位为符号位，以一个字节为例： | ||
|
|
||
| ```c | ||
| 0000 0011 // +3 | ||
| 1000 0011 // -3 需要进行补码处理，如果不进行补码处理，就存在两个0：-0和+0 | ||
| // 编码先减一再取反，符号位不变 -> 1000 0010 -> 1111 1101 | ||
| // 解码先取反再加一，符号位不变 -> 1000 0010 -> 1000 0011 | ||
| ``` | ||
|
|
||
| ### 运算符 | ||
| - 取反 ~(1001 0010)=(0110 1101) | ||
| - 与 (1001 0011)&(0011 1101)=(0001 0001) | ||
| - 位或 (1001 0011)|(0011 1101)=(1011 1111) | ||
| - 位异或 (1001 0011)^(0011 1101)=(1010 1110) | ||
| - 左移 | ||
| - 无符号数 (0000 0011)<<2=(0000 1100) | ||
| - 有符号数 (0010 0011)<<2=(1000 1100),由正数变成负数 | ||
| - 右移 | ||
| - 无符号数(0000 1100)>>2=(0000 0011) | ||
| - 有符号数 | ||
| - 算术右移(1000 1010)>>2=(1110 0010)，左端以1填充 | ||
| - 逻辑右移(1000 1010)>>2=(0010 0010)，左端以0填充 | ||
|
|
||
| ### 表示集合 | ||
|
|
||
| 这里以int为32位为例，表示有32个元素的集合 | ||
|
|
||
| ```c | ||
| // A=1011,则集合位{0,1,3} | ||
| // A, B | ||
| #define ALL_BITS 0xffff | ||
| A|B // 集合的并 | ||
| A&B // 集合的交 | ||
| A&~B // 集合的差A-B | ||
| ALL_BITS^A // A的补集 | ||
| A|=1<<bit // 添加特定元素 | ||
| A^=1<<bit // 清除特定元素 | ||
| A&=1<<bit // 取特定元素 | ||
| A&(1<<bit)==0 // 判断是否存在 | ||
| ``` | ||
| ## 实例 | ||
| ### 判断一个数为2的N次方 | ||
| ```c | ||
| bool isPowOfTwo(int n){ | ||
| return 0 == (n & (n-1)); | ||
| } | ||
| ``` | ||
|
|
||
|
|
||
|
|
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