YV12，I420，YUV420P的区别

YV12和I420的区别

一般来说，直接采集到的视频数据是RGB24的格式，RGB24一帧的大小size＝width×heigth×3 Bit，RGB32的size＝width×heigth×4，如果是I420（即YUV标准格式4：2：0）的数据量是 size＝width×heigth×1.5 Bit。
在采集到RGB24数据后，需要对这个格式的数据进行第一次压缩。即将图像的颜色空间由RGB2YUV。因为，X264在进行编码的时候需要标准的YUV（4：2：0）。但是这里需要注意的是，虽然YV12也是（4：2：0），但是YV12和I420的却是不同的，在存储空间上面有些区别。如下：
YV12 ： 亮度（行×列） ＋ V（行×列/4) + U（行×列/4）
I420 ： 亮度（行×列） ＋ U（行×列/4) + V（行×列/4）
可以看出，YV12和I420基本上是一样的，就是UV的顺序不同。

yuv420p就是I420格式，使用极其广泛，它的示意图：

#ifndef AVUTIL_PIXFMT_H
#define AVUTIL_PIXFMT_H

/**
 * @file
 * pixel format definitions
 *
 */

#include "libavutil/avconfig.h"

/**
 * Pixel format.
 *
 * @note
 * 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 (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 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 PixelFormat {
    PIX_FMT_NONE= -1,
    PIX_FMT_YUV420P, ///< planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)
    PIX_FMT_YUYV422, ///< packed YUV 4:2:2, 16bpp, Y0 Cb Y1 Cr
    PIX_FMT_RGB24, ///< packed RGB 8:8:8, 24bpp, RGBRGB...
    PIX_FMT_BGR24, ///< packed RGB 8:8:8, 24bpp, BGRBGR...
    PIX_FMT_YUV422P, ///< planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)
    PIX_FMT_YUV444P, ///< planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)
    PIX_FMT_YUV410P, ///< planar YUV 4:1:0, 9bpp, (1 Cr & Cb sample per 4x4 Y samples)
    PIX_FMT_YUV411P, ///< planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples)
    PIX_FMT_GRAY8, ///< Y , 8bpp
    PIX_FMT_MONOWHITE, ///< Y , 1bpp, 0 is white, 1 is black, in each byte pixels are ordered from the msb to the lsb
    PIX_FMT_MONOBLACK, ///< Y , 1bpp, 0 is black, 1 is white, in each byte pixels are ordered from the msb to the lsb
    PIX_FMT_PAL8, ///< 8 bit with PIX_FMT_RGB32 palette
    PIX_FMT_YUVJ420P, ///< planar YUV 4:2:0, 12bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV420P and setting color_range
    PIX_FMT_YUVJ422P, ///< planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV422P and setting color_range
    PIX_FMT_YUVJ444P, ///< planar YUV 4:4:4, 24bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV444P and setting color_range
    PIX_FMT_XVMC_MPEG2_MC,///< XVideo Motion Acceleration via common packet passing
    PIX_FMT_XVMC_MPEG2_IDCT,
    PIX_FMT_UYVY422, ///< packed YUV 4:2:2, 16bpp, Cb Y0 Cr Y1
    PIX_FMT_UYYVYY411, ///< packed YUV 4:1:1, 12bpp, Cb Y0 Y1 Cr Y2 Y3
    PIX_FMT_BGR8, ///< packed RGB 3:3:2, 8bpp, (msb)2B 3G 3R(lsb)
    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 bits
    PIX_FMT_BGR4_BYTE, ///< packed RGB 1:2:1, 8bpp, (msb)1B 2G 1R(lsb)
    PIX_FMT_RGB8, ///< packed RGB 3:3:2, 8bpp, (msb)2R 3G 3B(lsb)
    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 bits
    PIX_FMT_RGB4_BYTE, ///< packed RGB 1:2:1, 8bpp, (msb)1R 2G 1B(lsb)
    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)
    PIX_FMT_NV21, ///< as above, but U and V bytes are swapped

    PIX_FMT_ARGB, ///< packed ARGB 8:8:8:8, 32bpp, ARGBARGB...
    PIX_FMT_RGBA, ///< packed RGBA 8:8:8:8, 32bpp, RGBARGBA...
    PIX_FMT_ABGR, ///< packed ABGR 8:8:8:8, 32bpp, ABGRABGR...
    PIX_FMT_BGRA, ///< packed BGRA 8:8:8:8, 32bpp, BGRABGRA...

    PIX_FMT_GRAY16BE, ///< Y , 16bpp, big-endian
    PIX_FMT_GRAY16LE, ///< Y , 16bpp, little-endian
    PIX_FMT_YUV440P, ///< planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples)
    PIX_FMT_YUVJ440P, ///< planar YUV 4:4:0 full scale (JPEG), deprecated in favor of PIX_FMT_YUV440P and setting color_range
    PIX_FMT_YUVA420P, ///< planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)
    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 headers
    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 headers
    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 headers
    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 headers
    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
    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-endian
    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-endian

    PIX_FMT_RGB565BE, ///< packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), big-endian
    PIX_FMT_RGB565LE, ///< packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), little-endian
    PIX_FMT_RGB555BE, ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), big-endian, most significant bit to 0
    PIX_FMT_RGB555LE, ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), little-endian, most significant bit to 0

    PIX_FMT_BGR565BE, ///< packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), big-endian
    PIX_FMT_BGR565LE, ///< packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), little-endian
    PIX_FMT_BGR555BE, ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), big-endian, most significant bit to 1
    PIX_FMT_BGR555LE, ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), little-endian, most significant bit to 1

    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 headers
    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 headers
    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 headers

    PIX_FMT_YUV420P16LE, ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
    PIX_FMT_YUV420P16BE, ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian
    PIX_FMT_YUV422P16LE, ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
    PIX_FMT_YUV422P16BE, ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian
    PIX_FMT_YUV444P16LE, ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
    PIX_FMT_YUV444P16BE, ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian
    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
    PIX_FMT_DXVA2_VLD, ///< HW decoding through DXVA2, Picture.data[3] contains a LPDIRECT3DSURFACE9 pointer

    PIX_FMT_RGB444LE, ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), little-endian, most significant bits to 0
    PIX_FMT_RGB444BE, ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), big-endian, most significant bits to 0
    PIX_FMT_BGR444LE, ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), little-endian, most significant bits to 1
    PIX_FMT_BGR444BE, ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), big-endian, most significant bits to 1
    PIX_FMT_GRAY8A, ///< 8bit gray, 8bit alpha
    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-endian
    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 10 formats have the disadvantage of needing 1 format for each bit depth, thus
    //If you want to support multiple bit depths, then using PIX_FMT_YUV420P16* with the bpp stored seperately
    //is better
    PIX_FMT_YUV420P9BE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian
    PIX_FMT_YUV420P9LE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
    PIX_FMT_YUV420P10BE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian
    PIX_FMT_YUV420P10LE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian
    PIX_FMT_YUV422P10BE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian
    PIX_FMT_YUV422P10LE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
    PIX_FMT_YUV444P9BE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian
    PIX_FMT_YUV444P9LE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
    PIX_FMT_YUV444P10BE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian
    PIX_FMT_YUV444P10LE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian
    PIX_FMT_YUV422P9BE, ///< planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian
    PIX_FMT_YUV422P9LE, ///< planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian
    PIX_FMT_VDA_VLD, ///< hardware decoding through VDA

#ifdef AV_PIX_FMT_ABI_GIT_MASTER
    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-endian
    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-endian
    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-endian
    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
#endif
    PIX_FMT_GBRP, ///< planar GBR 4:4:4 24bpp
    PIX_FMT_GBRP9BE, ///< planar GBR 4:4:4 27bpp, big endian
    PIX_FMT_GBRP9LE, ///< planar GBR 4:4:4 27bpp, little endian
    PIX_FMT_GBRP10BE, ///< planar GBR 4:4:4 30bpp, big endian
    PIX_FMT_GBRP10LE, ///< planar GBR 4:4:4 30bpp, little endian
    PIX_FMT_GBRP16BE, ///< planar GBR 4:4:4 48bpp, big endian
    PIX_FMT_GBRP16LE, ///< planar GBR 4:4:4 48bpp, little endian

#ifndef AV_PIX_FMT_ABI_GIT_MASTER
    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-endian
    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-endian
    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-endian
    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
#endif
    PIX_FMT_0RGB=0x123+4, ///< packed RGB 8:8:8, 32bpp, 0RGB0RGB...
    PIX_FMT_RGB0, ///< packed RGB 8:8:8, 32bpp, RGB0RGB0...
    PIX_FMT_0BGR, ///< packed BGR 8:8:8, 32bpp, 0BGR0BGR...
    PIX_FMT_BGR0, ///< packed BGR 8:8:8, 32bpp, BGR0BGR0...
    PIX_FMT_YUVA444P, ///< planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)

    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
};

#define PIX_FMT_Y400A PIX_FMT_GRAY8A
#define PIX_FMT_GBR24P PIX_FMT_GBRP

#if AV_HAVE_BIGENDIAN
#   define PIX_FMT_NE(be, le) PIX_FMT_##be
#else
#   define PIX_FMT_NE(be, le) PIX_FMT_##le
#endif

#define PIX_FMT_RGB32   PIX_FMT_NE(ARGB, BGRA)
#define PIX_FMT_RGB32_1 PIX_FMT_NE(RGBA, ABGR)
#define PIX_FMT_BGR32   PIX_FMT_NE(ABGR, RGBA)
#define PIX_FMT_BGR32_1 PIX_FMT_NE(BGRA, ARGB)
#define PIX_FMT_0RGB32  PIX_FMT_NE(0RGB, BGR0)
#define PIX_FMT_0BGR32  PIX_FMT_NE(0BGR, RGB0)

#define PIX_FMT_GRAY16 PIX_FMT_NE(GRAY16BE, GRAY16LE)
#define PIX_FMT_RGB48  PIX_FMT_NE(RGB48BE, RGB48LE)
#define PIX_FMT_RGB565 PIX_FMT_NE(RGB565BE, RGB565LE)
#define PIX_FMT_RGB555 PIX_FMT_NE(RGB555BE, RGB555LE)
#define PIX_FMT_RGB444 PIX_FMT_NE(RGB444BE, RGB444LE)
#define PIX_FMT_BGR48  PIX_FMT_NE(BGR48BE, BGR48LE)
#define PIX_FMT_BGR565 PIX_FMT_NE(BGR565BE, BGR565LE)
#define PIX_FMT_BGR555 PIX_FMT_NE(BGR555BE, BGR555LE)
#define PIX_FMT_BGR444 PIX_FMT_NE(BGR444BE, BGR444LE)

#define PIX_FMT_YUV420P9  PIX_FMT_NE(YUV420P9BE , YUV420P9LE)
#define PIX_FMT_YUV422P9  PIX_FMT_NE(YUV422P9BE , YUV422P9LE)
#define PIX_FMT_YUV444P9  PIX_FMT_NE(YUV444P9BE , YUV444P9LE)
#define PIX_FMT_YUV420P10 PIX_FMT_NE(YUV420P10BE, YUV420P10LE)
#define PIX_FMT_YUV422P10 PIX_FMT_NE(YUV422P10BE, YUV422P10LE)
#define PIX_FMT_YUV444P10 PIX_FMT_NE(YUV444P10BE, YUV444P10LE)
#define PIX_FMT_YUV420P16 PIX_FMT_NE(YUV420P16BE, YUV420P16LE)
#define PIX_FMT_YUV422P16 PIX_FMT_NE(YUV422P16BE, YUV422P16LE)
#define PIX_FMT_YUV444P16 PIX_FMT_NE(YUV444P16BE, YUV444P16LE)

#define PIX_FMT_RGBA64 PIX_FMT_NE(RGBA64BE, RGBA64LE)
#define PIX_FMT_BGRA64 PIX_FMT_NE(BGRA64BE, BGRA64LE)
#define PIX_FMT_GBRP9     PIX_FMT_NE(GBRP9BE , GBRP9LE)
#define PIX_FMT_GBRP10    PIX_FMT_NE(GBRP10BE, GBRP10LE)
#define PIX_FMT_GBRP16    PIX_FMT_NE(GBRP16BE, GBRP16LE)

#endif /* AVUTIL_PIXFMT_H */

参考：
1，http://blog.csdn.net/leixiaohua1020/article/details/12234821
2，http://blog.csdn.net/leixiaohua1020/article/details/14215391