最简单的基于FFmpeg的libswscale的示例(YUV转RGB)
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最简单的基于FFmpeg的libswscale的示例系列文章列表:
最简单的基于FFmpeg的libswscale的示例(YUV转RGB)
最简单的基于FFmpeg的libswscale的示例附件:测试图片生成工具
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本文记录一个基于FFmpeg的libswscale的示例。Libswscale里面实现了各种图像像素格式的转换,例如YUV与RGB之间的转换;以及图像大小缩放(例如640x360拉伸为1280x720)功能。而且libswscale还做了相应指令集的优化,因此它的转换效率比自己写的C语言的转换效率高很多。
本文记录的程序将像素格式为YUV420P,分辨率为480x272的视频转换为像素格式为RGB24,分辨率为1280x720的视频。
流程
简单的初始化方法
Libswscale使用起来很方便,最主要的函数只有3个:
(1) sws_getContext():使用参数初始化SwsContext结构体。
(2) sws_scale():转换一帧图像。
(3) sws_freeContext():释放SwsContext结构体。
其中sws_getContext()也可以用另一个接口函数sws_getCachedContext()取代。
复杂但是更灵活的初始化方法
初始化SwsContext除了调用sws_getContext()之外还有另一种方法,更加灵活,可以配置更多的参数。该方法调用的函数如下所示。
(1) sws_alloc_context():为SwsContext结构体分配内存。
(2) av_opt_set_XXX():通过av_opt_set_int(),av_opt_set()…等等一系列方法设置SwsContext结构体的值。在这里需要注意,SwsContext结构体的定义看不到,所以不能对其中的成员变量直接进行赋值,必须通过av_opt_set()这类的API才能对其进行赋值。
(3) sws_init_context():初始化SwsContext结构体。
这种复杂的方法可以配置一些sws_getContext()配置不了的参数。比如说设置图像的YUV像素的取值范围是JPEG标准(Y、U、V取值范围都是0-255)还是MPEG标准(Y取值范围是16-235,U、V的取值范围是16-240)。
几个知识点
下文记录几个图像像素数据处理过程中的几个知识点:像素格式,图像拉伸,YUV像素取值范围,色域。
像素格式
像素格式的知识此前已经记录过,不再重复。在这里记录一下FFmpeg支持的像素格式。有几点注意事项:
(1) 所有的像素格式的名称都是以“AV_PIX_FMT_”开头
(2) 像素格式名称后面有“P”的,代表是planar格式,否则就是packed格式。Planar格式不同的分量分别存储在不同的数组中,例如AV_PIX_FMT_YUV420P存储方式如下:
data[0]: Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8……
data[1]: U1, U2, U3, U4……
data[2]: V1, V2, V3, V4……
Packed格式的数据都存储在同一个数组中,例如AV_PIX_FMT_RGB24存储方式如下:
data[0]: R1, G1, B1, R2, G2, B2, R3, G3, B3, R4, G4, B4……
(3) 像素格式名称后面有“BE”的,代表是Big Endian格式;名称后面有“LE”的,代表是Little Endian格式。
FFmpeg支持的像素格式的定义位于libavutil\pixfmt.h,是一个名称为AVPixelFormat的枚举类型,如下所示。
/*** Pixel format.** @note* AV_PIX_FMT_RGB32 is handled in an endian-specific manner. An RGBA* color is put together as:* (A << 24) | (R << 16) | (G << 8) | B* This is stored as BGRA on little-endian CPU architectures and ARGB on* big-endian CPUs.** @par* When the pixel format is palettized RGB (AV_PIX_FMT_PAL8), the palettized* image data is stored in AVFrame.data[0]. The palette is transported in* AVFrame.data[1], is 1024 bytes long (256 4-byte entries) and is* formatted the same as in AV_PIX_FMT_RGB32 described above (i.e., it is* also endian-specific). Note also that the individual RGB palette* components stored in AVFrame.data[1] should be in the range 0..255.* This is important as many custom PAL8 video codecs that were designed* to run on the IBM VGA graphics adapter use 6-bit palette components.** @par* For all the 8bit per pixel formats, an RGB32 palette is in data[1] like* for pal8. This palette is filled in automatically by the function* allocating the picture.** @note* Make sure that all newly added big-endian formats have (pix_fmt & 1) == 1* and that all newly added little-endian formats have (pix_fmt & 1) == 0.* This allows simpler detection of big vs little-endian.*/
enum AVPixelFormat {AV_PIX_FMT_NONE = -1,AV_PIX_FMT_YUV420P, ///< planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)AV_PIX_FMT_YUYV422, ///< packed YUV 4:2:2, 16bpp, Y0 Cb Y1 CrAV_PIX_FMT_RGB24, ///< packed RGB 8:8:8, 24bpp, RGBRGB...AV_PIX_FMT_BGR24, ///< packed RGB 8:8:8, 24bpp, BGRBGR...AV_PIX_FMT_YUV422P, ///< planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)AV_PIX_FMT_YUV444P, ///< planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)AV_PIX_FMT_YUV410P, ///< planar YUV 4:1:0, 9bpp, (1 Cr & Cb sample per 4x4 Y samples)AV_PIX_FMT_YUV411P, ///< planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples)AV_PIX_FMT_GRAY8, ///< Y , 8bppAV_PIX_FMT_MONOWHITE, ///< Y , 1bpp, 0 is white, 1 is black, in each byte pixels are ordered from the msb to the lsbAV_PIX_FMT_MONOBLACK, ///< Y , 1bpp, 0 is black, 1 is white, in each byte pixels are ordered from the msb to the lsbAV_PIX_FMT_PAL8, ///< 8 bit with PIX_FMT_RGB32 paletteAV_PIX_FMT_YUVJ420P, ///< planar YUV 4:2:0, 12bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV420P and setting color_rangeAV_PIX_FMT_YUVJ422P, ///< planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV422P and setting color_rangeAV_PIX_FMT_YUVJ444P, ///< planar YUV 4:4:4, 24bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV444P and setting color_range
#if FF_API_XVMCAV_PIX_FMT_XVMC_MPEG2_MC,///< XVideo Motion Acceleration via common packet passingAV_PIX_FMT_XVMC_MPEG2_IDCT,
#define AV_PIX_FMT_XVMC AV_PIX_FMT_XVMC_MPEG2_IDCT
#endif /* FF_API_XVMC */AV_PIX_FMT_UYVY422, ///< packed YUV 4:2:2, 16bpp, Cb Y0 Cr Y1AV_PIX_FMT_UYYVYY411, ///< packed YUV 4:1:1, 12bpp, Cb Y0 Y1 Cr Y2 Y3AV_PIX_FMT_BGR8, ///< packed RGB 3:3:2, 8bpp, (msb)2B 3G 3R(lsb)AV_PIX_FMT_BGR4, ///< packed RGB 1:2:1 bitstream, 4bpp, (msb)1B 2G 1R(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bitsAV_PIX_FMT_BGR4_BYTE, ///< packed RGB 1:2:1, 8bpp, (msb)1B 2G 1R(lsb)AV_PIX_FMT_RGB8, ///< packed RGB 3:3:2, 8bpp, (msb)2R 3G 3B(lsb)AV_PIX_FMT_RGB4, ///< packed RGB 1:2:1 bitstream, 4bpp, (msb)1R 2G 1B(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bitsAV_PIX_FMT_RGB4_BYTE, ///< packed RGB 1:2:1, 8bpp, (msb)1R 2G 1B(lsb)AV_PIX_FMT_NV12, ///< planar YUV 4:2:0, 12bpp, 1 plane for Y and 1 plane for the UV components, which are interleaved (first byte U and the following byte V)AV_PIX_FMT_NV21, ///< as above, but U and V bytes are swappedAV_PIX_FMT_ARGB, ///< packed ARGB 8:8:8:8, 32bpp, ARGBARGB...AV_PIX_FMT_RGBA, ///< packed RGBA 8:8:8:8, 32bpp, RGBARGBA...AV_PIX_FMT_ABGR, ///< packed ABGR 8:8:8:8, 32bpp, ABGRABGR...AV_PIX_FMT_BGRA, ///< packed BGRA 8:8:8:8, 32bpp, BGRABGRA...AV_PIX_FMT_GRAY16BE, ///< Y , 16bpp, big-endianAV_PIX_FMT_GRAY16LE, ///< Y , 16bpp, little-endianAV_PIX_FMT_YUV440P, ///< planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples)AV_PIX_FMT_YUVJ440P, ///< planar YUV 4:4:0 full scale (JPEG), deprecated in favor of PIX_FMT_YUV440P and setting color_rangeAV_PIX_FMT_YUVA420P, ///< planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)
#if FF_API_VDPAUAV_PIX_FMT_VDPAU_H264,///< H.264 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headersAV_PIX_FMT_VDPAU_MPEG1,///< MPEG-1 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headersAV_PIX_FMT_VDPAU_MPEG2,///< MPEG-2 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headersAV_PIX_FMT_VDPAU_WMV3,///< WMV3 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headersAV_PIX_FMT_VDPAU_VC1, ///< VC-1 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers
#endifAV_PIX_FMT_RGB48BE, ///< packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as big-endianAV_PIX_FMT_RGB48LE, ///< packed RGB 16:16:16, 48bpp, 16R, 16G, 16B, the 2-byte value for each R/G/B component is stored as little-endianAV_PIX_FMT_RGB565BE, ///< packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), big-endianAV_PIX_FMT_RGB565LE, ///< packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), little-endianAV_PIX_FMT_RGB555BE, ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), big-endian, most significant bit to 0AV_PIX_FMT_RGB555LE, ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), little-endian, most significant bit to 0AV_PIX_FMT_BGR565BE, ///< packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), big-endianAV_PIX_FMT_BGR565LE, ///< packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), little-endianAV_PIX_FMT_BGR555BE, ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), big-endian, most significant bit to 1AV_PIX_FMT_BGR555LE, ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), little-endian, most significant bit to 1AV_PIX_FMT_VAAPI_MOCO, ///< HW acceleration through VA API at motion compensation entry-point, Picture.data[3] contains a vaapi_render_state struct which contains macroblocks as well as various fields extracted from headersAV_PIX_FMT_VAAPI_IDCT, ///< HW acceleration through VA API at IDCT entry-point, Picture.data[3] contains a vaapi_render_state struct which contains fields extracted from headersAV_PIX_FMT_VAAPI_VLD, ///< HW decoding through VA API, Picture.data[3] contains a vaapi_render_state struct which contains the bitstream of the slices as well as various fields extracted from headersAV_PIX_FMT_YUV420P16LE, ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endianAV_PIX_FMT_YUV420P16BE, ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endianAV_PIX_FMT_YUV422P16LE, ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endianAV_PIX_FMT_YUV422P16BE, ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endianAV_PIX_FMT_YUV444P16LE, ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endianAV_PIX_FMT_YUV444P16BE, ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian
#if FF_API_VDPAUAV_PIX_FMT_VDPAU_MPEG4, ///< MPEG4 HW decoding with VDPAU, data[0] contains a vdpau_render_state struct which contains the bitstream of the slices as well as various fields extracted from headers
#endifAV_PIX_FMT_DXVA2_VLD, ///< HW decoding through DXVA2, Picture.data[3] contains a LPDIRECT3DSURFACE9 pointerAV_PIX_FMT_RGB444LE, ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), little-endian, most significant bits to 0AV_PIX_FMT_RGB444BE, ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), big-endian, most significant bits to 0AV_PIX_FMT_BGR444LE, ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), little-endian, most significant bits to 1AV_PIX_FMT_BGR444BE, ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), big-endian, most significant bits to 1AV_PIX_FMT_GRAY8A, ///< 8bit gray, 8bit alphaAV_PIX_FMT_BGR48BE, ///< packed RGB 16:16:16, 48bpp, 16B, 16G, 16R, the 2-byte value for each R/G/B component is stored as big-endianAV_PIX_FMT_BGR48LE, ///< packed RGB 16:16:16, 48bpp, 16B, 16G, 16R, the 2-byte value for each R/G/B component is stored as little-endian/*** The following 12 formats have the disadvantage of needing 1 format for each bit depth.* Notice that each 9/10 bits sample is stored in 16 bits with extra padding.* If you want to support multiple bit depths, then using AV_PIX_FMT_YUV420P16* with the bpp stored separately is better.*/AV_PIX_FMT_YUV420P9BE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endianAV_PIX_FMT_YUV420P9LE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endianAV_PIX_FMT_YUV420P10BE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endianAV_PIX_FMT_YUV420P10LE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endianAV_PIX_FMT_YUV422P10BE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endianAV_PIX_FMT_YUV422P10LE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endianAV_PIX_FMT_YUV444P9BE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endianAV_PIX_FMT_YUV444P9LE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endianAV_PIX_FMT_YUV444P10BE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endianAV_PIX_FMT_YUV444P10LE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endianAV_PIX_FMT_YUV422P9BE, ///< planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endianAV_PIX_FMT_YUV422P9LE, ///< planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endianAV_PIX_FMT_VDA_VLD, ///< hardware decoding through VDA#ifdef AV_PIX_FMT_ABI_GIT_MASTERAV_PIX_FMT_RGBA64BE, ///< packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is stored as big-endianAV_PIX_FMT_RGBA64LE, ///< packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is stored as little-endianAV_PIX_FMT_BGRA64BE, ///< packed RGBA 16:16:16:16, 64bpp, 16B, 16G, 16R, 16A, the 2-byte value for each R/G/B/A component is stored as big-endianAV_PIX_FMT_BGRA64LE, ///< packed RGBA 16:16:16:16, 64bpp, 16B, 16G, 16R, 16A, the 2-byte value for each R/G/B/A component is stored as little-endian
#endifAV_PIX_FMT_GBRP, ///< planar GBR 4:4:4 24bppAV_PIX_FMT_GBRP9BE, ///< planar GBR 4:4:4 27bpp, big-endianAV_PIX_FMT_GBRP9LE, ///< planar GBR 4:4:4 27bpp, little-endianAV_PIX_FMT_GBRP10BE, ///< planar GBR 4:4:4 30bpp, big-endianAV_PIX_FMT_GBRP10LE, ///< planar GBR 4:4:4 30bpp, little-endianAV_PIX_FMT_GBRP16BE, ///< planar GBR 4:4:4 48bpp, big-endianAV_PIX_FMT_GBRP16LE, ///< planar GBR 4:4:4 48bpp, little-endian/*** duplicated pixel formats for compatibility with libav.* FFmpeg supports these formats since May 8 2012 and Jan 28 2012 (commits f9ca1ac7 and 143a5c55)* Libav added them Oct 12 2012 with incompatible values (commit 6d5600e85)*/AV_PIX_FMT_YUVA422P_LIBAV, ///< planar YUV 4:2:2 24bpp, (1 Cr & Cb sample per 2x1 Y & A samples)AV_PIX_FMT_YUVA444P_LIBAV, ///< planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)AV_PIX_FMT_YUVA420P9BE, ///< planar YUV 4:2:0 22.5bpp, (1 Cr & Cb sample per 2x2 Y & A samples), big-endianAV_PIX_FMT_YUVA420P9LE, ///< planar YUV 4:2:0 22.5bpp, (1 Cr & Cb sample per 2x2 Y & A samples), little-endianAV_PIX_FMT_YUVA422P9BE, ///< planar YUV 4:2:2 27bpp, (1 Cr & Cb sample per 2x1 Y & A samples), big-endianAV_PIX_FMT_YUVA422P9LE, ///< planar YUV 4:2:2 27bpp, (1 Cr & Cb sample per 2x1 Y & A samples), little-endianAV_PIX_FMT_YUVA444P9BE, ///< planar YUV 4:4:4 36bpp, (1 Cr & Cb sample per 1x1 Y & A samples), big-endianAV_PIX_FMT_YUVA444P9LE, ///< planar YUV 4:4:4 36bpp, (1 Cr & Cb sample per 1x1 Y & A samples), little-endianAV_PIX_FMT_YUVA420P10BE, ///< planar YUV 4:2:0 25bpp, (1 Cr & Cb sample per 2x2 Y & A samples, big-endian)AV_PIX_FMT_YUVA420P10LE, ///< planar YUV 4:2:0 25bpp, (1 Cr & Cb sample per 2x2 Y & A samples, little-endian)AV_PIX_FMT_YUVA422P10BE, ///< planar YUV 4:2:2 30bpp, (1 Cr & Cb sample per 2x1 Y & A samples, big-endian)AV_PIX_FMT_YUVA422P10LE, ///< planar YUV 4:2:2 30bpp, (1 Cr & Cb sample per 2x1 Y & A samples, little-endian)AV_PIX_FMT_YUVA444P10BE, ///< planar YUV 4:4:4 40bpp, (1 Cr & Cb sample per 1x1 Y & A samples, big-endian)AV_PIX_FMT_YUVA444P10LE, ///< planar YUV 4:4:4 40bpp, (1 Cr & Cb sample per 1x1 Y & A samples, little-endian)AV_PIX_FMT_YUVA420P16BE, ///< planar YUV 4:2:0 40bpp, (1 Cr & Cb sample per 2x2 Y & A samples, big-endian)AV_PIX_FMT_YUVA420P16LE, ///< planar YUV 4:2:0 40bpp, (1 Cr & Cb sample per 2x2 Y & A samples, little-endian)AV_PIX_FMT_YUVA422P16BE, ///< planar YUV 4:2:2 48bpp, (1 Cr & Cb sample per 2x1 Y & A samples, big-endian)AV_PIX_FMT_YUVA422P16LE, ///< planar YUV 4:2:2 48bpp, (1 Cr & Cb sample per 2x1 Y & A samples, little-endian)AV_PIX_FMT_YUVA444P16BE, ///< planar YUV 4:4:4 64bpp, (1 Cr & Cb sample per 1x1 Y & A samples, big-endian)AV_PIX_FMT_YUVA444P16LE, ///< planar YUV 4:4:4 64bpp, (1 Cr & Cb sample per 1x1 Y & A samples, little-endian)AV_PIX_FMT_VDPAU, ///< HW acceleration through VDPAU, Picture.data[3] contains a VdpVideoSurfaceAV_PIX_FMT_XYZ12LE, ///< packed XYZ 4:4:4, 36 bpp, (msb) 12X, 12Y, 12Z (lsb), the 2-byte value for each X/Y/Z is stored as little-endian, the 4 lower bits are set to 0AV_PIX_FMT_XYZ12BE, ///< packed XYZ 4:4:4, 36 bpp, (msb) 12X, 12Y, 12Z (lsb), the 2-byte value for each X/Y/Z is stored as big-endian, the 4 lower bits are set to 0AV_PIX_FMT_NV16, ///< interleaved chroma YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)AV_PIX_FMT_NV20LE, ///< interleaved chroma YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endianAV_PIX_FMT_NV20BE, ///< interleaved chroma YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian/*** duplicated pixel formats for compatibility with libav.* FFmpeg supports these formats since Sat Sep 24 06:01:45 2011 +0200 (commits 9569a3c9f41387a8c7d1ce97d8693520477a66c3)* also see Fri Nov 25 01:38:21 2011 +0100 92afb431621c79155fcb7171d26f137eb1bee028* Libav added them Sun Mar 16 23:05:47 2014 +0100 with incompatible values (commit 1481d24c3a0abf81e1d7a514547bd5305232be30)*/AV_PIX_FMT_RGBA64BE_LIBAV, ///< packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is stored as big-endianAV_PIX_FMT_RGBA64LE_LIBAV, ///< packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is stored as little-endianAV_PIX_FMT_BGRA64BE_LIBAV, ///< packed RGBA 16:16:16:16, 64bpp, 16B, 16G, 16R, 16A, the 2-byte value for each R/G/B/A component is stored as big-endianAV_PIX_FMT_BGRA64LE_LIBAV, ///< packed RGBA 16:16:16:16, 64bpp, 16B, 16G, 16R, 16A, the 2-byte value for each R/G/B/A component is stored as little-endianAV_PIX_FMT_YVYU422, ///< packed YUV 4:2:2, 16bpp, Y0 Cr Y1 Cb#ifndef AV_PIX_FMT_ABI_GIT_MASTERAV_PIX_FMT_RGBA64BE=0x123, ///< packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is stored as big-endianAV_PIX_FMT_RGBA64LE, ///< packed RGBA 16:16:16:16, 64bpp, 16R, 16G, 16B, 16A, the 2-byte value for each R/G/B/A component is stored as little-endianAV_PIX_FMT_BGRA64BE, ///< packed RGBA 16:16:16:16, 64bpp, 16B, 16G, 16R, 16A, the 2-byte value for each R/G/B/A component is stored as big-endianAV_PIX_FMT_BGRA64LE, ///< packed RGBA 16:16:16:16, 64bpp, 16B, 16G, 16R, 16A, the 2-byte value for each R/G/B/A component is stored as little-endian
#endifAV_PIX_FMT_0RGB=0x123+4, ///< packed RGB 8:8:8, 32bpp, 0RGB0RGB...AV_PIX_FMT_RGB0, ///< packed RGB 8:8:8, 32bpp, RGB0RGB0...AV_PIX_FMT_0BGR, ///< packed BGR 8:8:8, 32bpp, 0BGR0BGR...AV_PIX_FMT_BGR0, ///< packed BGR 8:8:8, 32bpp, BGR0BGR0...AV_PIX_FMT_YUVA444P, ///< planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)AV_PIX_FMT_YUVA422P, ///< planar YUV 4:2:2 24bpp, (1 Cr & Cb sample per 2x1 Y & A samples)AV_PIX_FMT_YUV420P12BE, ///< planar YUV 4:2:0,18bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endianAV_PIX_FMT_YUV420P12LE, ///< planar YUV 4:2:0,18bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endianAV_PIX_FMT_YUV420P14BE, ///< planar YUV 4:2:0,21bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endianAV_PIX_FMT_YUV420P14LE, ///< planar YUV 4:2:0,21bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endianAV_PIX_FMT_YUV422P12BE, ///< planar YUV 4:2:2,24bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endianAV_PIX_FMT_YUV422P12LE, ///< planar YUV 4:2:2,24bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endianAV_PIX_FMT_YUV422P14BE, ///< planar YUV 4:2:2,28bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endianAV_PIX_FMT_YUV422P14LE, ///< planar YUV 4:2:2,28bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endianAV_PIX_FMT_YUV444P12BE, ///< planar YUV 4:4:4,36bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endianAV_PIX_FMT_YUV444P12LE, ///< planar YUV 4:4:4,36bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endianAV_PIX_FMT_YUV444P14BE, ///< planar YUV 4:4:4,42bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endianAV_PIX_FMT_YUV444P14LE, ///< planar YUV 4:4:4,42bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endianAV_PIX_FMT_GBRP12BE, ///< planar GBR 4:4:4 36bpp, big-endianAV_PIX_FMT_GBRP12LE, ///< planar GBR 4:4:4 36bpp, little-endianAV_PIX_FMT_GBRP14BE, ///< planar GBR 4:4:4 42bpp, big-endianAV_PIX_FMT_GBRP14LE, ///< planar GBR 4:4:4 42bpp, little-endianAV_PIX_FMT_GBRAP, ///< planar GBRA 4:4:4:4 32bppAV_PIX_FMT_GBRAP16BE, ///< planar GBRA 4:4:4:4 64bpp, big-endianAV_PIX_FMT_GBRAP16LE, ///< planar GBRA 4:4:4:4 64bpp, little-endianAV_PIX_FMT_YUVJ411P, ///< planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples) full scale (JPEG), deprecated in favor of PIX_FMT_YUV411P and setting color_rangeAV_PIX_FMT_BAYER_BGGR8, ///< bayer, BGBG..(odd line), GRGR..(even line), 8-bit samples */AV_PIX_FMT_BAYER_RGGB8, ///< bayer, RGRG..(odd line), GBGB..(even line), 8-bit samples */AV_PIX_FMT_BAYER_GBRG8, ///< bayer, GBGB..(odd line), RGRG..(even line), 8-bit samples */AV_PIX_FMT_BAYER_GRBG8, ///< bayer, GRGR..(odd line), BGBG..(even line), 8-bit samples */AV_PIX_FMT_BAYER_BGGR16LE, ///< bayer, BGBG..(odd line), GRGR..(even line), 16-bit samples, little-endian */AV_PIX_FMT_BAYER_BGGR16BE, ///< bayer, BGBG..(odd line), GRGR..(even line), 16-bit samples, big-endian */AV_PIX_FMT_BAYER_RGGB16LE, ///< bayer, RGRG..(odd line), GBGB..(even line), 16-bit samples, little-endian */AV_PIX_FMT_BAYER_RGGB16BE, ///< bayer, RGRG..(odd line), GBGB..(even line), 16-bit samples, big-endian */AV_PIX_FMT_BAYER_GBRG16LE, ///< bayer, GBGB..(odd line), RGRG..(even line), 16-bit samples, little-endian */AV_PIX_FMT_BAYER_GBRG16BE, ///< bayer, GBGB..(odd line), RGRG..(even line), 16-bit samples, big-endian */AV_PIX_FMT_BAYER_GRBG16LE, ///< bayer, GRGR..(odd line), BGBG..(even line), 16-bit samples, little-endian */AV_PIX_FMT_BAYER_GRBG16BE, ///< bayer, GRGR..(odd line), BGBG..(even line), 16-bit samples, big-endian */
#if !FF_API_XVMCAV_PIX_FMT_XVMC,///< XVideo Motion Acceleration via common packet passing
#endif /* !FF_API_XVMC */AV_PIX_FMT_NB, ///< number of pixel formats, DO NOT USE THIS if you want to link with shared libav* because the number of formats might differ between versions#if FF_API_PIX_FMT
#include "old_pix_fmts.h"
#endif
};
FFmpeg有一个专门用于描述像素格式的结构体AVPixFmtDescriptor。该结构体的定义位于libavutil\pixdesc.h,如下所示。
/*** Descriptor that unambiguously describes how the bits of a pixel are* stored in the up to 4 data planes of an image. It also stores the* subsampling factors and number of components.** @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV* and all the YUV variants) AVPixFmtDescriptor just stores how values* are stored not what these values represent.*/
typedef struct AVPixFmtDescriptor{const char *name;uint8_t nb_components; ///< The number of components each pixel has, (1-4)/*** Amount to shift the luma width right to find the chroma width.* For YV12 this is 1 for example.* chroma_width = -((-luma_width) >> log2_chroma_w)* The note above is needed to ensure rounding up.* This value only refers to the chroma components.*/uint8_t log2_chroma_w; ///< chroma_width = -((-luma_width )>>log2_chroma_w)/*** Amount to shift the luma height right to find the chroma height.* For YV12 this is 1 for example.* chroma_height= -((-luma_height) >> log2_chroma_h)* The note above is needed to ensure rounding up.* This value only refers to the chroma components.*/uint8_t log2_chroma_h;uint8_t flags;/*** Parameters that describe how pixels are packed.* If the format has 2 or 4 components, then alpha is last.* If the format has 1 or 2 components, then luma is 0.* If the format has 3 or 4 components,* if the RGB flag is set then 0 is red, 1 is green and 2 is blue;* otherwise 0 is luma, 1 is chroma-U and 2 is chroma-V.*/AVComponentDescriptor comp[4];
}AVPixFmtDescriptor;
关于AVPixFmtDescriptor这个结构体不再做过多解释。它的定义比较简单,看注释就可以理解。通过av_pix_fmt_desc_get()可以获得指定像素格式的AVPixFmtDescriptor结构体。
/*** @return a pixel format descriptor for provided pixel format or NULL if* this pixel format is unknown.*/
const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt);
通过AVPixFmtDescriptor结构体可以获得不同像素格式的一些信息。例如下文中用到了av_get_bits_per_pixel(),通过该函数可以获得指定像素格式每个像素占用的比特数(Bit Per Pixel)。
/*** Return the number of bits per pixel used by the pixel format* described by pixdesc. Note that this is not the same as the number* of bits per sample.** The returned number of bits refers to the number of bits actually* used for storing the pixel information, that is padding bits are* not counted.*/
int av_get_bits_per_pixel(const AVPixFmtDescriptor *pixdesc);
其他的API在这里不做过多记录。
图像拉伸
FFmpeg支持多种像素拉伸的方式。这些方式的定义位于libswscale\swscale.h中,如下所示。
#define SWS_FAST_BILINEAR 1
#define SWS_BILINEAR 2
#define SWS_BICUBIC 4
#define SWS_X 8
#define SWS_POINT 0x10
#define SWS_AREA 0x20
#define SWS_BICUBLIN 0x40
#define SWS_GAUSS 0x80
#define SWS_SINC 0x100
#define SWS_LANCZOS 0x200
#define SWS_SPLINE 0x400
其中SWS_BICUBIC性能比较好;SWS_FAST_BILINEAR在性能和速度之间有一个比好好的平衡,
而SWS_POINT的效果比较差。
有关这些方法的评测可以参考文章:
《ffmpeg中的sws_scale算法性能测试》
简单解释一下SWS_BICUBIC、SWS_BILINEAR和SWS_POINT的原理。
SWS_POINT(Nearest-neighbor interpolation, 邻域插值)
领域插值可以简单说成“1个点确定插值的点”。例如当图像放大后,新的样点根据距离它最近的样点的值取得自己的值。换句话说就是简单拷贝附近距离它最近的样点的值。领域插值是一种最基础的插值方法,速度最快,插值效果最不好,一般情况下不推荐使用。一般情况下使用邻域插值之后,画面会产生很多的“锯齿”。下图显示了4x4=16个彩色样点经过邻域插值后形成的图形。
SWS_BILINEAR(Bilinear interpolation, 双线性插值)
双线性插值可以简单说成“4个点确定插值的点”。它的计算过程可以简单用下图表示。图中绿色的P点是需要插值的点。首先通过Q11,Q21求得R1;Q12,Q22求得R2。然后根据R1,R2求得P。
其中求值的过程是一个简单的加权计算的过程。
设定Q11 = (x1, y1),Q12 = (x1, y2),Q21 = (x2, y1),Q22 = (x2, y2)则各点的计算公式如下。
可以看出距离插值的点近一些的样点权值会大一些,远一些的样点权值要小一些。
下面看一个维基百科上的双线性插值的实例。该例子根据坐标为(20, 14), (20, 15), (21, 14),(21, 15)的4个样点计算坐标为(20.2, 14.5)的插值点的值。
SWS_BICUBIC(Bicubic interpolation, 双三次插值)
双三次插值可以简单说成“16个点确定插值的点”。该插值算法比前两种算法复杂很多,插值后图像的质量也是最好的。有关它的插值方式比较复杂不再做过多记录。它的差值方法可以简单表述为下述公式。
其中aij的过程依赖于插值数据的特性。
维基百科上使用同样的样点进行邻域插值,双线性插值,双三次插值对比如下图所示。
Bilinear interpolation,双线性插值
YUV像素取值范围
FFmpeg中可以通过使用av_opt_set()设置“src_range”和“dst_range”来设置输入和输出的YUV的取值范围。如果“dst_range”字段设置为“1”的话,则代表输出的YUV的取值范围遵循“jpeg”标准;如果“dst_range”字段设置为“0”的话,则代表输出的YUV的取值范围遵循“mpeg”标准。下面记录一下YUV的取值范围的概念。
与RGB每个像素点的每个分量取值范围为0-255不同(每个分量占8bit),YUV取值范围有两种:
(1) 以Rec.601为代表(还包括BT.709 / BT.2020)的广播电视标准中,Y的取值范围是16-235,U、V的取值范围是16-240。FFmpeg中称之为“mpeg”范围。
(2) 以JPEG为代表的标准中,Y、U、V的取值范围都是0-255。FFmpeg中称之为“jpeg” 范围。
实际中最常见的是第1种取值范围的YUV(可以自己观察一下YUV的数据,会发现其中亮度分量没有取值为0、255这样的数值)。很多人在这个地方会有疑惑,为什么会去掉“两边”的取值呢?
在广播电视系统中不传输很低和很高的数值,实际上是为了防止信号变动造成过载,因而把这“两边”的数值作为“保护带”。下面这张图是数字电视中亮度信号量化后的电平分配图。从图中可以看出,对于8bit量化来说,信号的白电平为235,对应模拟电平为700mV;黑电平为16,对应模拟电平为0mV。信号上方的“保护带”取值范围是236至254,而信号下方的“保护带”取值范围是1-15。最边缘的0和255两个电平是保护电平,是不允许出现在数据流中的。与之类似,10bit量化的时候,白电平是235*4=940,黑电平是16*4=64。
下面两张图是数字电视中色度信号量化后的电平分配图。可以看出,色度最大正电平为240,对应模拟电平为+350mV;色度最大负电平为16,对应模拟电平为-350mV。需要注意的是,色度信号数字电平128对应的模拟电平是0mV。
色域
Libswscale支持色域的转换。有关色域的转换我目前还没有做太多的研究,仅记录一下目前最常见的三个标准中的色域:BT.601,BT.709,BT.2020。这三个标准中的色域逐渐增大。
在这里先简单解释一下CIE 1931颜色空间。这个空间围绕的区域像一个“舌头”,其中包含了自然界所有的颜色。CIE 1931颜色空间中的横坐标是x,纵坐标是y,x、y、z满足如下关系:
“舌头”的边缘叫做“舌形曲线”,代表着饱和度为100%的光谱色。“舌头”的中心点(1/3,1/3)对应着白色,饱和度为0。
受显示器件性能的限制,电视屏幕是无法重现所有的颜色的,尤其是位于“舌形曲线”上的100% 饱和度的光谱色一般情况下是无法显示出来的。因此电视屏幕只能根据其具体的荧光粉的配方,有选择性的显示一部分的颜色,这部分可以显示的颜色称为色域。下文分别比较标清电视、高清电视和超高清电视标准中规定的色域。可以看出随着技术的进步,色域的范围正变得越来越大。
标清电视(SDTV)色域的规定源自于BT.601。高清电视(HDTV)色域的规定源自于BT.709。他们两个标准中的色域在CIE 1931颜色空间中的对比如下图所示。从图中可以看出,BT.709和BT.601色域差别不大,BT.709的色域要略微大于BT.601。
超高清电视(UHDTV)色域的规定源自于BT.2020。BT.2020和BT.709的色域在CIE 1931 颜色空间中的对比如下图所示。从图中可以看出,BT.2020的色域要远远大于BT.709。
从上面的对比也可以看出,对超高清电视(UHDTV)的显示器件的性能的要求更高了。这样超高清电视可以还原出一个更“真实”的世界。
下面这张图则使用实际的例子反映出色域范围大的重要性。图中的两个黑色三角形分别标识出了BT.709(小三角形)和BT.2020(大三角形)标准中的色域。从图中可以看出,如果使用色域较小的显示设备显示图片的话,将会损失掉很多的颜色。
源代码
本示例程序包含一个输入和一个输出,实现了从输入图像格式(YUV420P)到输出图像格式(RGB24)之间的转换;同时将输入视频的分辨率从480x272拉伸为1280x720。
/*** 最简单的基于FFmpeg的Swscale示例* Simplest FFmpeg Swscale** 雷霄骅 Lei Xiaohua* leixiaohua1020@126.com* 中国传媒大学/数字电视技术* Communication University of China / Digital TV Technology* http://blog.csdn.net/leixiaohua1020** 本程序使用libswscale对像素数据进行缩放转换等处理。* 它中实现了YUV420P格式转换为RGB24格式,* 同时将分辨率从480x272拉伸为1280x720* 它是最简单的libswscale的教程。** This software uses libswscale to scale / convert pixels.* It convert YUV420P format to RGB24 format,* and changes resolution from 480x272 to 1280x720.* It's the simplest tutorial about libswscale.*/#include <stdio.h>#define __STDC_CONSTANT_MACROS#ifdef _WIN32
//Windows
extern "C"
{
#include "libswscale/swscale.h"
#include "libavutil/opt.h"
#include "libavutil/imgutils.h"
};
#else
//Linux...
#ifdef __cplusplus
extern "C"
{
#endif
#include <libswscale/swscale.h>
#include <libavutil/opt.h>
#include <libavutil/imgutils.h>
#ifdef __cplusplus
};
#endif
#endifint main(int argc, char* argv[])
{//Parameters FILE *src_file =fopen("sintel_480x272_yuv420p.yuv", "rb");const int src_w=480,src_h=272;AVPixelFormat src_pixfmt=AV_PIX_FMT_YUV420P;int src_bpp=av_get_bits_per_pixel(av_pix_fmt_desc_get(src_pixfmt));FILE *dst_file = fopen("sintel_1280x720_rgb24.rgb", "wb");const int dst_w=1280,dst_h=720;AVPixelFormat dst_pixfmt=AV_PIX_FMT_RGB24;int dst_bpp=av_get_bits_per_pixel(av_pix_fmt_desc_get(dst_pixfmt));//Structuresuint8_t *src_data[4];int src_linesize[4];uint8_t *dst_data[4];int dst_linesize[4];int rescale_method=SWS_BICUBIC;struct SwsContext *img_convert_ctx;uint8_t *temp_buffer=(uint8_t *)malloc(src_w*src_h*src_bpp/8);int frame_idx=0;int ret=0;ret= av_image_alloc(src_data, src_linesize,src_w, src_h, src_pixfmt, 1);if (ret< 0) {printf( "Could not allocate source image\n");return -1;}ret = av_image_alloc(dst_data, dst_linesize,dst_w, dst_h, dst_pixfmt, 1);if (ret< 0) {printf( "Could not allocate destination image\n");return -1;}//----------------------------- //Init Method 1img_convert_ctx =sws_alloc_context();//Show AVOptionav_opt_show2(img_convert_ctx,stdout,AV_OPT_FLAG_VIDEO_PARAM,0);//Set Valueav_opt_set_int(img_convert_ctx,"sws_flags",SWS_BICUBIC|SWS_PRINT_INFO,0);av_opt_set_int(img_convert_ctx,"srcw",src_w,0);av_opt_set_int(img_convert_ctx,"srch",src_h,0);av_opt_set_int(img_convert_ctx,"src_format",src_pixfmt,0);//'0' for MPEG (Y:0-235);'1' for JPEG (Y:0-255)av_opt_set_int(img_convert_ctx,"src_range",1,0);av_opt_set_int(img_convert_ctx,"dstw",dst_w,0);av_opt_set_int(img_convert_ctx,"dsth",dst_h,0);av_opt_set_int(img_convert_ctx,"dst_format",dst_pixfmt,0);av_opt_set_int(img_convert_ctx,"dst_range",1,0);sws_init_context(img_convert_ctx,NULL,NULL);//Init Method 2//img_convert_ctx = sws_getContext(src_w, src_h,src_pixfmt, dst_w, dst_h, dst_pixfmt, // rescale_method, NULL, NULL, NULL); //-----------------------------/*//Colorspaceret=sws_setColorspaceDetails(img_convert_ctx,sws_getCoefficients(SWS_CS_ITU601),0,sws_getCoefficients(SWS_CS_ITU709),0,0, 1 << 16, 1 << 16);if (ret==-1) {printf( "Colorspace not support.\n");return -1;}*/while(1){if (fread(temp_buffer, 1, src_w*src_h*src_bpp/8, src_file) != src_w*src_h*src_bpp/8){break;}switch(src_pixfmt){case AV_PIX_FMT_GRAY8:{memcpy(src_data[0],temp_buffer,src_w*src_h);break;}case AV_PIX_FMT_YUV420P:{memcpy(src_data[0],temp_buffer,src_w*src_h); //Ymemcpy(src_data[1],temp_buffer+src_w*src_h,src_w*src_h/4); //Umemcpy(src_data[2],temp_buffer+src_w*src_h*5/4,src_w*src_h/4); //Vbreak;}case AV_PIX_FMT_YUV422P:{memcpy(src_data[0],temp_buffer,src_w*src_h); //Ymemcpy(src_data[1],temp_buffer+src_w*src_h,src_w*src_h/2); //Umemcpy(src_data[2],temp_buffer+src_w*src_h*3/2,src_w*src_h/2); //Vbreak;}case AV_PIX_FMT_YUV444P:{memcpy(src_data[0],temp_buffer,src_w*src_h); //Ymemcpy(src_data[1],temp_buffer+src_w*src_h,src_w*src_h); //Umemcpy(src_data[2],temp_buffer+src_w*src_h*2,src_w*src_h); //Vbreak;}case AV_PIX_FMT_YUYV422:{memcpy(src_data[0],temp_buffer,src_w*src_h*2); //Packedbreak;}case AV_PIX_FMT_RGB24:{memcpy(src_data[0],temp_buffer,src_w*src_h*3); //Packedbreak;}default:{printf("Not Support Input Pixel Format.\n");break;}}sws_scale(img_convert_ctx, src_data, src_linesize, 0, src_h, dst_data, dst_linesize);printf("Finish process frame %5d\n",frame_idx);frame_idx++;switch(dst_pixfmt){case AV_PIX_FMT_GRAY8:{fwrite(dst_data[0],1,dst_w*dst_h,dst_file); break;}case AV_PIX_FMT_YUV420P:{fwrite(dst_data[0],1,dst_w*dst_h,dst_file); //Yfwrite(dst_data[1],1,dst_w*dst_h/4,dst_file); //Ufwrite(dst_data[2],1,dst_w*dst_h/4,dst_file); //Vbreak;}case AV_PIX_FMT_YUV422P:{fwrite(dst_data[0],1,dst_w*dst_h,dst_file); //Yfwrite(dst_data[1],1,dst_w*dst_h/2,dst_file); //Ufwrite(dst_data[2],1,dst_w*dst_h/2,dst_file); //Vbreak;}case AV_PIX_FMT_YUV444P:{fwrite(dst_data[0],1,dst_w*dst_h,dst_file); //Yfwrite(dst_data[1],1,dst_w*dst_h,dst_file); //Ufwrite(dst_data[2],1,dst_w*dst_h,dst_file); //Vbreak;}case AV_PIX_FMT_YUYV422:{fwrite(dst_data[0],1,dst_w*dst_h*2,dst_file); //Packedbreak;}case AV_PIX_FMT_RGB24:{fwrite(dst_data[0],1,dst_w*dst_h*3,dst_file); //Packedbreak;}default:{printf("Not Support Output Pixel Format.\n");break;}}}sws_freeContext(img_convert_ctx);free(temp_buffer);fclose(dst_file);av_freep(&src_data[0]);av_freep(&dst_data[0]);return 0;
}
运行结果
程序的输入为一个名称为“sintel_480x272_yuv420p.yuv”的视频。该视频像素格式是YUV420P,分辨率为480x272。
程序的输出为一个名称为“sintel_1280x720_rgb24.rgb”的视频。该视频像素格式是RGB24,分辨率为1280x720。
下载
Simplest FFmpeg Swscale
项目主页
SourceForge:https://sourceforge.net/projects/simplestffmpegswscale/
Github:https://github.com/leixiaohua1020/simplest_ffmpeg_swscale
开源中国:http://git.oschina.net/leixiaohua1020/simplest_ffmpeg_swscale
CDSN下载地址:http://download.csdn.net/detail/leixiaohua1020/8292175
本教程是最简单的基于FFmpeg的libswscale进行像素处理的教程。它包含了两个工程:
simplest_ffmpeg_swscale: 最简单的libswscale的教程。
simplest_pic_gen: 生成各种测试图片的工具。
更新-1.1 (2015.2.13)=========================================
这次考虑到了跨平台的要求,调整了源代码。经过这次调整之后,源代码可以在以下平台编译通过:
VC++:打开sln文件即可编译,无需配置。
cl.exe:打开compile_cl.bat即可命令行下使用cl.exe进行编译,注意可能需要按照VC的安装路径调整脚本里面的参数。编译命令如下。
::VS2010 Environment
call "D:\Program Files\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"
::include
@set INCLUDE=include;%INCLUDE%
::lib
@set LIB=lib;%LIB%
::compile and link
cl simplest_ffmpeg_swscale.cpp /link swscale.lib avutil.lib /OPT:NOREF
MinGW:MinGW命令行下运行compile_mingw.sh即可使用MinGW的g++进行编译。编译命令如下。
g++ simplest_ffmpeg_swscale.cpp -g -o simplest_ffmpeg_swscale.exe \
-I /usr/local/include -L /usr/local/lib -lswscale -lavutil
GCC:Linux或者MacOS命令行下运行compile_gcc.sh即可使用GCC进行编译。编译命令如下。
gcc simplest_ffmpeg_swscale.cpp -g -o simplest_ffmpeg_swscale.out -I /usr/local/include -L /usr/local/lib \
-lswscale -lavutil
PS:相关的编译命令已经保存到了工程文件夹中
CSDN下载地址:http://download.csdn.net/detail/leixiaohua1020/8445671
SourceForge上已经更新。
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