sws_getContext用法实例

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ffmpeg中sws_scale()用法实例

sws_getContext用法实例

视频编码 2009-06-30 10:16:57 阅读782 评论1  字号：大中小 订阅

struct SwsContext* sws_getContext(int srcW, int srcH, int srcFormat, int dstW, int dstH, int dstFormat, int flags, SwsFilter *srcFilter, SwsFilter *dstFilter, double *param)

Returns an SwsContext to be used in sws_scale.

Params:
srcW, srcH, srcFormat: source width, height, and pix format
dstW, dstH, dstFormat: destination width, height, and pix format
flags: Method of scaling to use. Choices are SWS_FAST_BILINEAR, SWS_BILINEAR, SWS_BICUBIC, SWS_X, SWS_POINT, SWS_AREA, SWS_BICUBLIN, SWS_GAUSS, SWS_SINC, SWS_LANCZOS, SWS_SPLINE. Other flags include CPU capability flags: SWS_CPU_CAPS_MMX, SWS_CPU_CAPS_MMX2, SWS_CPU_CAPS_3DNOW, SWS_CPU_CAPS_ALTIVEC. Other flags include (currently not completely implemented) SWS_FULL_CHR_H_INT, SWS_FULL_CHR_H_INP, and SWS_DIRECT_BGR. Finally we have SWS_ACCURATE_RND and perhaps the most useful for beginners, SWS_PRINT_INFO. I have no idea what most of these do. Maybe email me?
srcFilter, dstFilter: SwsFilter for source and destination. SwsFilter involves chroma/luminsence filtering. A value of NULL sets these to the default.
param: should be a pointer to an int[2] buffer with coefficients. Not documented. Looks like it's used to alter the default scaling algorithms slightly. A value of NULL sets this to the default. Experts only!

使用方法如下：

#define W 96
#define H 96

struct SwsContext *sws;

sws= sws_getContext(W/12, H/12, PIX_FMT_RGB32, W, H, PIX_FMT_YUV420P, 2, NULL, NULL, NULL);

用途：

sws_scale(sws, rgb_src, rgb_stride, 0, H, src, stride);