最简单的基于FFmpeg的libswscale的示例（YUV转RGB）

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。

1. /**

2. * Pixel format.

3. *

4. * @note

5. * AV_PIX_FMT_RGB32 is handled in an endian-specific manner. An RGBA

6. * color is put together as:

7. * (A << 24) | (R << 16) | (G << 8) | B

8. * This is stored as BGRA on little-endian CPU architectures and ARGB on

9. * big-endian CPUs.

10. *

11. * @par

12. * When the pixel format is palettized RGB (AV_PIX_FMT_PAL8), the palettized

13. * image data is stored in AVFrame.data[0]. The palette is transported in

14. * AVFrame.data[1], is 1024 bytes long (256 4-byte entries) and is

15. * formatted the same as in AV_PIX_FMT_RGB32 described above (i.e., it is

16. * also endian-specific). Note also that the individual RGB palette

17. * components stored in AVFrame.data[1] should be in the range 0..255.

18. * This is important as many custom PAL8 video codecs that were designed

19. * to run on the IBM VGA graphics adapter use 6-bit palette components.

20. *

21. * @par

22. * For all the 8bit per pixel formats, an RGB32 palette is in data[1] like

23. * for pal8. This palette is filled in automatically by the function

24. * allocating the picture.

25. *

26. * @note

27. * Make sure that all newly added big-endian formats have (pix_fmt & 1) == 1

28. * and that all newly added little-endian formats have (pix_fmt & 1) == 0.

29. * This allows simpler detection of big vs little-endian.

30. */

31. enum AVPixelFormat {

32. AV_PIX_FMT_NONE = -1,

33. AV_PIX_FMT_YUV420P, ///< planar YUV 4:2:0, 12bpp, (1 Cr & Cb sample per 2x2 Y samples)

34. AV_PIX_FMT_YUYV422, ///< packed YUV 4:2:2, 16bpp, Y0 Cb Y1 Cr

35. AV_PIX_FMT_RGB24, ///< packed RGB 8:8:8, 24bpp, RGBRGB...

36. AV_PIX_FMT_BGR24, ///< packed RGB 8:8:8, 24bpp, BGRBGR...

37. AV_PIX_FMT_YUV422P, ///< planar YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)

38. AV_PIX_FMT_YUV444P, ///< planar YUV 4:4:4, 24bpp, (1 Cr & Cb sample per 1x1 Y samples)

39. AV_PIX_FMT_YUV410P, ///< planar YUV 4:1:0, 9bpp, (1 Cr & Cb sample per 4x4 Y samples)

40. AV_PIX_FMT_YUV411P, ///< planar YUV 4:1:1, 12bpp, (1 Cr & Cb sample per 4x1 Y samples)

41. AV_PIX_FMT_GRAY8, ///< Y , 8bpp

42. AV_PIX_FMT_MONOWHITE, ///< Y , 1bpp, 0 is white, 1 is black, in each byte pixels are ordered from the msb to the lsb

43. AV_PIX_FMT_MONOBLACK, ///< Y , 1bpp, 0 is black, 1 is white, in each byte pixels are ordered from the msb to the lsb

44. AV_PIX_FMT_PAL8, ///< 8 bit with PIX_FMT_RGB32 palette

45. AV_PIX_FMT_YUVJ420P, ///< planar YUV 4:2:0, 12bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV420P and setting color_range

46. AV_PIX_FMT_YUVJ422P, ///< planar YUV 4:2:2, 16bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV422P and setting color_range

47. AV_PIX_FMT_YUVJ444P, ///< planar YUV 4:4:4, 24bpp, full scale (JPEG), deprecated in favor of PIX_FMT_YUV444P and setting color_range

48. #if FF_API_XVMC

49. AV_PIX_FMT_XVMC_MPEG2_MC,///< XVideo Motion Acceleration via common packet passing

50. AV_PIX_FMT_XVMC_MPEG2_IDCT,

51. #define AV_PIX_FMT_XVMC AV_PIX_FMT_XVMC_MPEG2_IDCT

52. #endif /* FF_API_XVMC */

53. AV_PIX_FMT_UYVY422, ///< packed YUV 4:2:2, 16bpp, Cb Y0 Cr Y1

54. AV_PIX_FMT_UYYVYY411, ///< packed YUV 4:1:1, 12bpp, Cb Y0 Y1 Cr Y2 Y3

55. AV_PIX_FMT_BGR8, ///< packed RGB 3:3:2, 8bpp, (msb)2B 3G 3R(lsb)

56. 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 bits

57. AV_PIX_FMT_BGR4_BYTE, ///< packed RGB 1:2:1, 8bpp, (msb)1B 2G 1R(lsb)

58. AV_PIX_FMT_RGB8, ///< packed RGB 3:3:2, 8bpp, (msb)2R 3G 3B(lsb)

59. 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 bits

60. AV_PIX_FMT_RGB4_BYTE, ///< packed RGB 1:2:1, 8bpp, (msb)1R 2G 1B(lsb)

61. 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)

62. AV_PIX_FMT_NV21, ///< as above, but U and V bytes are swapped

63.  

64. AV_PIX_FMT_ARGB, ///< packed ARGB 8:8:8:8, 32bpp, ARGBARGB...

65. AV_PIX_FMT_RGBA, ///< packed RGBA 8:8:8:8, 32bpp, RGBARGBA...

66. AV_PIX_FMT_ABGR, ///< packed ABGR 8:8:8:8, 32bpp, ABGRABGR...

67. AV_PIX_FMT_BGRA, ///< packed BGRA 8:8:8:8, 32bpp, BGRABGRA...

68.  

69. AV_PIX_FMT_GRAY16BE, ///< Y , 16bpp, big-endian

70. AV_PIX_FMT_GRAY16LE, ///< Y , 16bpp, little-endian

71. AV_PIX_FMT_YUV440P, ///< planar YUV 4:4:0 (1 Cr & Cb sample per 1x2 Y samples)

72. AV_PIX_FMT_YUVJ440P, ///< planar YUV 4:4:0 full scale (JPEG), deprecated in favor of PIX_FMT_YUV440P and setting color_range

73. AV_PIX_FMT_YUVA420P, ///< planar YUV 4:2:0, 20bpp, (1 Cr & Cb sample per 2x2 Y & A samples)

74. #if FF_API_VDPAU

75. AV_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

76. AV_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

77. AV_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

78. AV_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

79. AV_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

80. #endif

81. AV_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

82. AV_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

83.  

84. AV_PIX_FMT_RGB565BE, ///< packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), big-endian

85. AV_PIX_FMT_RGB565LE, ///< packed RGB 5:6:5, 16bpp, (msb) 5R 6G 5B(lsb), little-endian

86. AV_PIX_FMT_RGB555BE, ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), big-endian, most significant bit to 0

87. AV_PIX_FMT_RGB555LE, ///< packed RGB 5:5:5, 16bpp, (msb)1A 5R 5G 5B(lsb), little-endian, most significant bit to 0

88.  

89. AV_PIX_FMT_BGR565BE, ///< packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), big-endian

90. AV_PIX_FMT_BGR565LE, ///< packed BGR 5:6:5, 16bpp, (msb) 5B 6G 5R(lsb), little-endian

91. AV_PIX_FMT_BGR555BE, ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), big-endian, most significant bit to 1

92. AV_PIX_FMT_BGR555LE, ///< packed BGR 5:5:5, 16bpp, (msb)1A 5B 5G 5R(lsb), little-endian, most significant bit to 1

93.  

94. AV_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

95. AV_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

96. AV_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

97.  

98. AV_PIX_FMT_YUV420P16LE, ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian

99. AV_PIX_FMT_YUV420P16BE, ///< planar YUV 4:2:0, 24bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian

100. AV_PIX_FMT_YUV422P16LE, ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian

101. AV_PIX_FMT_YUV422P16BE, ///< planar YUV 4:2:2, 32bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian

102. AV_PIX_FMT_YUV444P16LE, ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian

103. AV_PIX_FMT_YUV444P16BE, ///< planar YUV 4:4:4, 48bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian

104. #if FF_API_VDPAU

105. AV_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

106. #endif

107. AV_PIX_FMT_DXVA2_VLD, ///< HW decoding through DXVA2, Picture.data[3] contains a LPDIRECT3DSURFACE9 pointer

108.  

109. AV_PIX_FMT_RGB444LE, ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), little-endian, most significant bits to 0

110. AV_PIX_FMT_RGB444BE, ///< packed RGB 4:4:4, 16bpp, (msb)4A 4R 4G 4B(lsb), big-endian, most significant bits to 0

111. AV_PIX_FMT_BGR444LE, ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), little-endian, most significant bits to 1

112. AV_PIX_FMT_BGR444BE, ///< packed BGR 4:4:4, 16bpp, (msb)4A 4B 4G 4R(lsb), big-endian, most significant bits to 1

113. AV_PIX_FMT_GRAY8A, ///< 8bit gray, 8bit alpha

114. AV_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

115. AV_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

116.  

117. /**

118. * The following 12 formats have the disadvantage of needing 1 format for each bit depth.

119. * Notice that each 9/10 bits sample is stored in 16 bits with extra padding.

120. * If you want to support multiple bit depths, then using AV_PIX_FMT_YUV420P16* with the bpp stored separately is better.

121. */

122. AV_PIX_FMT_YUV420P9BE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian

123. AV_PIX_FMT_YUV420P9LE, ///< planar YUV 4:2:0, 13.5bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian

124. AV_PIX_FMT_YUV420P10BE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian

125. AV_PIX_FMT_YUV420P10LE,///< planar YUV 4:2:0, 15bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian

126. AV_PIX_FMT_YUV422P10BE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian

127. AV_PIX_FMT_YUV422P10LE,///< planar YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian

128. AV_PIX_FMT_YUV444P9BE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian

129. AV_PIX_FMT_YUV444P9LE, ///< planar YUV 4:4:4, 27bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian

130. AV_PIX_FMT_YUV444P10BE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian

131. AV_PIX_FMT_YUV444P10LE,///< planar YUV 4:4:4, 30bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian

132. AV_PIX_FMT_YUV422P9BE, ///< planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian

133. AV_PIX_FMT_YUV422P9LE, ///< planar YUV 4:2:2, 18bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian

134. AV_PIX_FMT_VDA_VLD, ///< hardware decoding through VDA

135.  

136. #ifdef AV_PIX_FMT_ABI_GIT_MASTER

137. AV_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

138. AV_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

139. AV_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

140. AV_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

141. #endif

142. AV_PIX_FMT_GBRP, ///< planar GBR 4:4:4 24bpp

143. AV_PIX_FMT_GBRP9BE, ///< planar GBR 4:4:4 27bpp, big-endian

144. AV_PIX_FMT_GBRP9LE, ///< planar GBR 4:4:4 27bpp, little-endian

145. AV_PIX_FMT_GBRP10BE, ///< planar GBR 4:4:4 30bpp, big-endian

146. AV_PIX_FMT_GBRP10LE, ///< planar GBR 4:4:4 30bpp, little-endian

147. AV_PIX_FMT_GBRP16BE, ///< planar GBR 4:4:4 48bpp, big-endian

148. AV_PIX_FMT_GBRP16LE, ///< planar GBR 4:4:4 48bpp, little-endian

149.  

150. /**

151. * duplicated pixel formats for compatibility with libav.

152. * FFmpeg supports these formats since May 8 2012 and Jan 28 2012 (commits f9ca1ac7 and 143a5c55)

153. * Libav added them Oct 12 2012 with incompatible values (commit 6d5600e85)

154. */

155. AV_PIX_FMT_YUVA422P_LIBAV, ///< planar YUV 4:2:2 24bpp, (1 Cr & Cb sample per 2x1 Y & A samples)

156. AV_PIX_FMT_YUVA444P_LIBAV, ///< planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)

157.  

158. AV_PIX_FMT_YUVA420P9BE, ///< planar YUV 4:2:0 22.5bpp, (1 Cr & Cb sample per 2x2 Y & A samples), big-endian

159. AV_PIX_FMT_YUVA420P9LE, ///< planar YUV 4:2:0 22.5bpp, (1 Cr & Cb sample per 2x2 Y & A samples), little-endian

160. AV_PIX_FMT_YUVA422P9BE, ///< planar YUV 4:2:2 27bpp, (1 Cr & Cb sample per 2x1 Y & A samples), big-endian

161. AV_PIX_FMT_YUVA422P9LE, ///< planar YUV 4:2:2 27bpp, (1 Cr & Cb sample per 2x1 Y & A samples), little-endian

162. AV_PIX_FMT_YUVA444P9BE, ///< planar YUV 4:4:4 36bpp, (1 Cr & Cb sample per 1x1 Y & A samples), big-endian

163. AV_PIX_FMT_YUVA444P9LE, ///< planar YUV 4:4:4 36bpp, (1 Cr & Cb sample per 1x1 Y & A samples), little-endian

164. AV_PIX_FMT_YUVA420P10BE, ///< planar YUV 4:2:0 25bpp, (1 Cr & Cb sample per 2x2 Y & A samples, big-endian)

165. AV_PIX_FMT_YUVA420P10LE, ///< planar YUV 4:2:0 25bpp, (1 Cr & Cb sample per 2x2 Y & A samples, little-endian)

166. AV_PIX_FMT_YUVA422P10BE, ///< planar YUV 4:2:2 30bpp, (1 Cr & Cb sample per 2x1 Y & A samples, big-endian)

167. AV_PIX_FMT_YUVA422P10LE, ///< planar YUV 4:2:2 30bpp, (1 Cr & Cb sample per 2x1 Y & A samples, little-endian)

168. AV_PIX_FMT_YUVA444P10BE, ///< planar YUV 4:4:4 40bpp, (1 Cr & Cb sample per 1x1 Y & A samples, big-endian)

169. AV_PIX_FMT_YUVA444P10LE, ///< planar YUV 4:4:4 40bpp, (1 Cr & Cb sample per 1x1 Y & A samples, little-endian)

170. AV_PIX_FMT_YUVA420P16BE, ///< planar YUV 4:2:0 40bpp, (1 Cr & Cb sample per 2x2 Y & A samples, big-endian)

171. AV_PIX_FMT_YUVA420P16LE, ///< planar YUV 4:2:0 40bpp, (1 Cr & Cb sample per 2x2 Y & A samples, little-endian)

172. AV_PIX_FMT_YUVA422P16BE, ///< planar YUV 4:2:2 48bpp, (1 Cr & Cb sample per 2x1 Y & A samples, big-endian)

173. AV_PIX_FMT_YUVA422P16LE, ///< planar YUV 4:2:2 48bpp, (1 Cr & Cb sample per 2x1 Y & A samples, little-endian)

174. AV_PIX_FMT_YUVA444P16BE, ///< planar YUV 4:4:4 64bpp, (1 Cr & Cb sample per 1x1 Y & A samples, big-endian)

175. AV_PIX_FMT_YUVA444P16LE, ///< planar YUV 4:4:4 64bpp, (1 Cr & Cb sample per 1x1 Y & A samples, little-endian)

176.  

177. AV_PIX_FMT_VDPAU, ///< HW acceleration through VDPAU, Picture.data[3] contains a VdpVideoSurface

178.  

179. AV_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 0

180. AV_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 0

181. AV_PIX_FMT_NV16, ///< interleaved chroma YUV 4:2:2, 16bpp, (1 Cr & Cb sample per 2x1 Y samples)

182. AV_PIX_FMT_NV20LE, ///< interleaved chroma YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian

183. AV_PIX_FMT_NV20BE, ///< interleaved chroma YUV 4:2:2, 20bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian

184.  

185. /**

186. * duplicated pixel formats for compatibility with libav.

187. * FFmpeg supports these formats since Sat Sep 24 06:01:45 2011 +0200 (commits 9569a3c9f41387a8c7d1ce97d8693520477a66c3)

188. * also see Fri Nov 25 01:38:21 2011 +0100 92afb431621c79155fcb7171d26f137eb1bee028

189. * Libav added them Sun Mar 16 23:05:47 2014 +0100 with incompatible values (commit 1481d24c3a0abf81e1d7a514547bd5305232be30)

190. */

191. 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-endian

192. AV_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-endian

193. AV_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-endian

194. AV_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-endian

195.  

196. AV_PIX_FMT_YVYU422, ///< packed YUV 4:2:2, 16bpp, Y0 Cr Y1 Cb

197.  

198. #ifndef AV_PIX_FMT_ABI_GIT_MASTER

199. AV_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

200. AV_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

201. AV_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

202. AV_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

203. #endif

204. AV_PIX_FMT_0RGB=0x123+4, ///< packed RGB 8:8:8, 32bpp, 0RGB0RGB...

205. AV_PIX_FMT_RGB0, ///< packed RGB 8:8:8, 32bpp, RGB0RGB0...

206. AV_PIX_FMT_0BGR, ///< packed BGR 8:8:8, 32bpp, 0BGR0BGR...

207. AV_PIX_FMT_BGR0, ///< packed BGR 8:8:8, 32bpp, BGR0BGR0...

208. AV_PIX_FMT_YUVA444P, ///< planar YUV 4:4:4 32bpp, (1 Cr & Cb sample per 1x1 Y & A samples)

209. AV_PIX_FMT_YUVA422P, ///< planar YUV 4:2:2 24bpp, (1 Cr & Cb sample per 2x1 Y & A samples)

210.  

211. AV_PIX_FMT_YUV420P12BE, ///< planar YUV 4:2:0,18bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian

212. AV_PIX_FMT_YUV420P12LE, ///< planar YUV 4:2:0,18bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian

213. AV_PIX_FMT_YUV420P14BE, ///< planar YUV 4:2:0,21bpp, (1 Cr & Cb sample per 2x2 Y samples), big-endian

214. AV_PIX_FMT_YUV420P14LE, ///< planar YUV 4:2:0,21bpp, (1 Cr & Cb sample per 2x2 Y samples), little-endian

215. AV_PIX_FMT_YUV422P12BE, ///< planar YUV 4:2:2,24bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian

216. AV_PIX_FMT_YUV422P12LE, ///< planar YUV 4:2:2,24bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian

217. AV_PIX_FMT_YUV422P14BE, ///< planar YUV 4:2:2,28bpp, (1 Cr & Cb sample per 2x1 Y samples), big-endian

218. AV_PIX_FMT_YUV422P14LE, ///< planar YUV 4:2:2,28bpp, (1 Cr & Cb sample per 2x1 Y samples), little-endian

219. AV_PIX_FMT_YUV444P12BE, ///< planar YUV 4:4:4,36bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian

220. AV_PIX_FMT_YUV444P12LE, ///< planar YUV 4:4:4,36bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian

221. AV_PIX_FMT_YUV444P14BE, ///< planar YUV 4:4:4,42bpp, (1 Cr & Cb sample per 1x1 Y samples), big-endian

222. AV_PIX_FMT_YUV444P14LE, ///< planar YUV 4:4:4,42bpp, (1 Cr & Cb sample per 1x1 Y samples), little-endian

223. AV_PIX_FMT_GBRP12BE, ///< planar GBR 4:4:4 36bpp, big-endian

224. AV_PIX_FMT_GBRP12LE, ///< planar GBR 4:4:4 36bpp, little-endian

225. AV_PIX_FMT_GBRP14BE, ///< planar GBR 4:4:4 42bpp, big-endian

226. AV_PIX_FMT_GBRP14LE, ///< planar GBR 4:4:4 42bpp, little-endian

227. AV_PIX_FMT_GBRAP, ///< planar GBRA 4:4:4:4 32bpp

228. AV_PIX_FMT_GBRAP16BE, ///< planar GBRA 4:4:4:4 64bpp, big-endian

229. AV_PIX_FMT_GBRAP16LE, ///< planar GBRA 4:4:4:4 64bpp, little-endian

230. AV_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_range

231.  

232. AV_PIX_FMT_BAYER_BGGR8, ///< bayer, BGBG..(odd line), GRGR..(even line), 8-bit samples */

233. AV_PIX_FMT_BAYER_RGGB8, ///< bayer, RGRG..(odd line), GBGB..(even line), 8-bit samples */

234. AV_PIX_FMT_BAYER_GBRG8, ///< bayer, GBGB..(odd line), RGRG..(even line), 8-bit samples */

235. AV_PIX_FMT_BAYER_GRBG8, ///< bayer, GRGR..(odd line), BGBG..(even line), 8-bit samples */

236. AV_PIX_FMT_BAYER_BGGR16LE, ///< bayer, BGBG..(odd line), GRGR..(even line), 16-bit samples, little-endian */

237. AV_PIX_FMT_BAYER_BGGR16BE, ///< bayer, BGBG..(odd line), GRGR..(even line), 16-bit samples, big-endian */

238. AV_PIX_FMT_BAYER_RGGB16LE, ///< bayer, RGRG..(odd line), GBGB..(even line), 16-bit samples, little-endian */

239. AV_PIX_FMT_BAYER_RGGB16BE, ///< bayer, RGRG..(odd line), GBGB..(even line), 16-bit samples, big-endian */

240. AV_PIX_FMT_BAYER_GBRG16LE, ///< bayer, GBGB..(odd line), RGRG..(even line), 16-bit samples, little-endian */

241. AV_PIX_FMT_BAYER_GBRG16BE, ///< bayer, GBGB..(odd line), RGRG..(even line), 16-bit samples, big-endian */

242. AV_PIX_FMT_BAYER_GRBG16LE, ///< bayer, GRGR..(odd line), BGBG..(even line), 16-bit samples, little-endian */

243. AV_PIX_FMT_BAYER_GRBG16BE, ///< bayer, GRGR..(odd line), BGBG..(even line), 16-bit samples, big-endian */

244. #if !FF_API_XVMC

245. AV_PIX_FMT_XVMC,///< XVideo Motion Acceleration via common packet passing

246. #endif /* !FF_API_XVMC */

247.  

248. 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

249.  

250. #if FF_API_PIX_FMT

251. #include "old_pix_fmts.h"

252. #endif

253. };

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。

1. /**

2. * Descriptor that unambiguously describes how the bits of a pixel are

3. * stored in the up to 4 data planes of an image. It also stores the

4. * subsampling factors and number of components.

5. *

6. * @note This is separate of the colorspace (RGB, YCbCr, YPbPr, JPEG-style YUV

7. * and all the YUV variants) AVPixFmtDescriptor just stores how values

8. * are stored not what these values represent.

9. */

10. typedef struct AVPixFmtDescriptor{

11. const char *name;

12. uint8_t nb_components; ///< The number of components each pixel has, (1-4)

13.  

14. /**

15. * Amount to shift the luma width right to find the chroma width.

16. * For YV12 this is 1 for example.

17. * chroma_width = -((-luma_width) >> log2_chroma_w)

18. * The note above is needed to ensure rounding up.

19. * This value only refers to the chroma components.

20. */

21. uint8_t log2_chroma_w; ///< chroma_width = -((-luma_width )>>log2_chroma_w)

22.  

23. /**

24. * Amount to shift the luma height right to find the chroma height.

25. * For YV12 this is 1 for example.

26. * chroma_height= -((-luma_height) >> log2_chroma_h)

27. * The note above is needed to ensure rounding up.

28. * This value only refers to the chroma components.

29. */

30. uint8_t log2_chroma_h;

31. uint8_t flags;

32.  

33. /**

34. * Parameters that describe how pixels are packed.

35. * If the format has 2 or 4 components, then alpha is last.

36. * If the format has 1 or 2 components, then luma is 0.

37. * If the format has 3 or 4 components,

38. * if the RGB flag is set then 0 is red, 1 is green and 2 is blue;

39. * otherwise 0 is luma, 1 is chroma-U and 2 is chroma-V.

40. */

41. AVComponentDescriptor comp[4];

42. }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。

1. /**

2. * @return a pixel format descriptor for provided pixel format or NULL if

3. * this pixel format is unknown.

4. */

5. 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）。

1. /**

2. * Return the number of bits per pixel used by the pixel format

3. * described by pixdesc. Note that this is not the same as the number

4. * of bits per sample.

5. *

6. * The returned number of bits refers to the number of bits actually

7. * used for storing the pixel information, that is padding bits are

8. * not counted.

9. */

10. 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。

1. #define SWS_FAST_BILINEAR 1

2. #define SWS_BILINEAR 2

3. #define SWS_BICUBIC 4

4. #define SWS_X 8

5. #define SWS_POINT 0x10

6. #define SWS_AREA 0x20

7. #define SWS_BICUBLIN 0x40

8. #define SWS_GAUSS 0x80

9. #define SWS_SINC 0x100

10. #define SWS_LANCZOS 0x200

11. #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。

Nearest-neighbor interpolation，邻域插值

Bilinear interpolation，双线性插值

Bicubic interpolation，双三次插值

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：

x + y + z = 1

“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。
 

1. /**

2. * 最简单的基于FFmpeg的Swscale示例

3. * Simplest FFmpeg Swscale

4. *

5. * 雷霄骅 Lei Xiaohua

6. * [email protected]

7. * 中国传媒大学/数字电视技术

8. * Communication University of China / Digital TV Technology

9. * http://blog.csdn.net/leixiaohua1020

10. *

11. * 本程序使用libswscale对像素数据进行缩放转换等处理。

12. * 它中实现了YUV420P格式转换为RGB24格式，

13. * 同时将分辨率从480x272拉伸为1280x720

14. * 它是最简单的libswscale的教程。

15. *

16. * This software uses libswscale to scale / convert pixels.

17. * It convert YUV420P format to RGB24 format,

18. * and changes resolution from 480x272 to 1280x720.

19. * It's the simplest tutorial about libswscale.

20. */

21.  

22. #include <stdio.h>

23.  

24. #define __STDC_CONSTANT_MACROS

25.  

26. #ifdef _WIN32

27. //Windows

28. extern "C"

29. {

30. #include "libswscale/swscale.h"

31. #include "libavutil/opt.h"

32. #include "libavutil/imgutils.h"

33. };

34. #else

35. //Linux...

36. #ifdef __cplusplus

37. extern "C"

38. {

39. #endif

40. #include <libswscale/swscale.h>

41. #include <libavutil/opt.h>

42. #include <libavutil/imgutils.h>

43. #ifdef __cplusplus

44. };

45. #endif

46. #endif

47.  
48.  

49. int main(int argc, char* argv[])

50. {

51. //Parameters

52. FILE *src_file =fopen("sintel_480x272_yuv420p.yuv", "rb");

53. const int src_w=480,src_h=272;

54. AVPixelFormat src_pixfmt=AV_PIX_FMT_YUV420P;

55.  

56. int src_bpp=av_get_bits_per_pixel(av_pix_fmt_desc_get(src_pixfmt));

57.  

58. FILE *dst_file = fopen("sintel_1280x720_rgb24.rgb", "wb");

59. const int dst_w=1280,dst_h=720;

60. AVPixelFormat dst_pixfmt=AV_PIX_FMT_RGB24;

61. int dst_bpp=av_get_bits_per_pixel(av_pix_fmt_desc_get(dst_pixfmt));

62.  

63. //Structures

64. uint8_t *src_data[4];

65. int src_linesize[4];

66.  

67. uint8_t *dst_data[4];

68. int dst_linesize[4];

69.  

70. int rescale_method=SWS_BICUBIC;

71. struct SwsContext *img_convert_ctx;

72. uint8_t *temp_buffer=(uint8_t *)malloc(src_w*src_h*src_bpp/8);

73.  

74. int frame_idx=0;

75. int ret=0;

76. ret= av_image_alloc(src_data, src_linesize,src_w, src_h, src_pixfmt, 1);

77. if (ret< 0) {

78. printf( "Could not allocate source image\n");

79. return -1;

80. }

81. ret = av_image_alloc(dst_data, dst_linesize,dst_w, dst_h, dst_pixfmt, 1);

82. if (ret< 0) {

83. printf( "Could not allocate destination image\n");

84. return -1;

85. }

86. //-----------------------------

87. //Init Method 1

88. img_convert_ctx =sws_alloc_context();

89. //Show AVOption

90. av_opt_show2(img_convert_ctx,stdout,AV_OPT_FLAG_VIDEO_PARAM,0);

91. //Set Value

92. av_opt_set_int(img_convert_ctx,"sws_flags",SWS_BICUBIC|SWS_PRINT_INFO,0);

93. av_opt_set_int(img_convert_ctx,"srcw",src_w,0);

94. av_opt_set_int(img_convert_ctx,"srch",src_h,0);

95. av_opt_set_int(img_convert_ctx,"src_format",src_pixfmt,0);

96. //'0' for MPEG (Y:0-235);'1' for JPEG (Y:0-255)

97. av_opt_set_int(img_convert_ctx,"src_range",1,0);

98. av_opt_set_int(img_convert_ctx,"dstw",dst_w,0);

99. av_opt_set_int(img_convert_ctx,"dsth",dst_h,0);

100. av_opt_set_int(img_convert_ctx,"dst_format",dst_pixfmt,0);

101. av_opt_set_int(img_convert_ctx,"dst_range",1,0);

102. sws_init_context(img_convert_ctx,NULL,NULL);

103.  

104. //Init Method 2

105. //img_convert_ctx = sws_getContext(src_w, src_h,src_pixfmt, dst_w, dst_h, dst_pixfmt,

106. // rescale_method, NULL, NULL, NULL);

107. //-----------------------------

108. /*

109. //Colorspace

110. ret=sws_setColorspaceDetails(img_convert_ctx,sws_getCoefficients(SWS_CS_ITU601),0,

111. sws_getCoefficients(SWS_CS_ITU709),0,

112. 0, 1 << 16, 1 << 16);

113. if (ret==-1) {

114. printf( "Colorspace not support.\n");

115. return -1;

116. }

117. */

118. while(1)

119. {

120. if (fread(temp_buffer, 1, src_w*src_h*src_bpp/8, src_file) != src_w*src_h*src_bpp/8){

121. break;

122. }

123.  

124. switch(src_pixfmt){

125. case AV_PIX_FMT_GRAY8:{

126. memcpy(src_data[0],temp_buffer,src_w*src_h);

127. break;

128. }

129. case AV_PIX_FMT_YUV420P:{

130. memcpy(src_data[0],temp_buffer,src_w*src_h); //Y

131. memcpy(src_data[1],temp_buffer+src_w*src_h,src_w*src_h/4); //U

132. memcpy(src_data[2],temp_buffer+src_w*src_h*5/4,src_w*src_h/4); //V

133. break;

134. }

135. case AV_PIX_FMT_YUV422P:{

136. memcpy(src_data[0],temp_buffer,src_w*src_h); //Y

137. memcpy(src_data[1],temp_buffer+src_w*src_h,src_w*src_h/2); //U

138. memcpy(src_data[2],temp_buffer+src_w*src_h*3/2,src_w*src_h/2); //V

139. break;

140. }

141. case AV_PIX_FMT_YUV444P:{

142. memcpy(src_data[0],temp_buffer,src_w*src_h); //Y

143. memcpy(src_data[1],temp_buffer+src_w*src_h,src_w*src_h); //U

144. memcpy(src_data[2],temp_buffer+src_w*src_h*2,src_w*src_h); //V

145. break;

146. }

147. case AV_PIX_FMT_YUYV422:{

148. memcpy(src_data[0],temp_buffer,src_w*src_h*2); //Packed

149. break;

150. }

151. case AV_PIX_FMT_RGB24:{

152. memcpy(src_data[0],temp_buffer,src_w*src_h*3); //Packed

153. break;

154. }

155. default:{

156. printf("Not Support Input Pixel Format.\n");

157. break;

158. }

159. }

160.  

161. sws_scale(img_convert_ctx, src_data, src_linesize, 0, src_h, dst_data, dst_linesize);

162. printf("Finish process frame %5d\n",frame_idx);

163. frame_idx++;

164.  

165. switch(dst_pixfmt){

166. case AV_PIX_FMT_GRAY8:{

167. fwrite(dst_data[0],1,dst_w*dst_h,dst_file);

168. break;

169. }

170. case AV_PIX_FMT_YUV420P:{

171. fwrite(dst_data[0],1,dst_w*dst_h,dst_file); //Y

172. fwrite(dst_data[1],1,dst_w*dst_h/4,dst_file); //U

173. fwrite(dst_data[2],1,dst_w*dst_h/4,dst_file); //V

174. break;

175. }

176. case AV_PIX_FMT_YUV422P:{

177. fwrite(dst_data[0],1,dst_w*dst_h,dst_file); //Y

178. fwrite(dst_data[1],1,dst_w*dst_h/2,dst_file); //U

179. fwrite(dst_data[2],1,dst_w*dst_h/2,dst_file); //V

180. break;

181. }

182. case AV_PIX_FMT_YUV444P:{

183. fwrite(dst_data[0],1,dst_w*dst_h,dst_file); //Y

184. fwrite(dst_data[1],1,dst_w*dst_h,dst_file); //U

185. fwrite(dst_data[2],1,dst_w*dst_h,dst_file); //V

186. break;

187. }

188. case AV_PIX_FMT_YUYV422:{

189. fwrite(dst_data[0],1,dst_w*dst_h*2,dst_file); //Packed

190. break;

191. }

192. case AV_PIX_FMT_RGB24:{

193. fwrite(dst_data[0],1,dst_w*dst_h*3,dst_file); //Packed

194. break;

195. }

196. default:{

197. printf("Not Support Output Pixel Format.\n");

198. break;

199. }

200. }

201. }

202.  

203. sws_freeContext(img_convert_ctx);

204.  

205. free(temp_buffer);

206. fclose(dst_file);

207. av_freep(&src_data[0]);

208. av_freep(&dst_data[0]);

209.  

210. return 0;

211. }

 

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。