参考：
https://blog.csdn.net/boonya/article/details/79753091
https://blog.csdn.net/u010029439/article/details/84754395
先谢谢两位大神！
可参考ffmpeg的源码，doc\examples\filtering_video.c，视频滤波的例子，对ffmpeg中 \libavfilter\vf_eq.c，亮度和对比度等调整来实现增强画质目的。
参考命令行：
ffmpeg.exe -i test.mp4 -vf eq=contrast=1:brightness=0.1 out.mp4
设置亮度、对比度、饱和度和近似伽马(gamma)调整
滤镜支持下面选项：
contrast
设置contrast表达式，值必须是一个-2.0-2.0间的浮点数，默认为0
brightness
设置brightness表达式.值必须是一个-1.0-1.0间的浮点数，默认为0
saturation
设置saturation表达式. 值必须是一个0-3.0间的浮点数，默认为1
————————————————
public unsafe class VideoFiltering {
#region 类成员变量
AVFilterGraph* m_filter_graph =null;
AVFilterContext* m_buffersink_ctx =null;
AVFilterContext* m_buffersrc_ctx =null;
AVFrame* m_filt_frame =null;
Object m_lock_record =new Object();
#endregion
public int Init(int width, int height, int contrast, int brightness) {
lock (m_lock_record) {
// Critical code section
if (m_filter_graph != null)
return -1;
contrast = contrast < 1 ? 1 : contrast;
contrast = contrast > 9 ? 9 : contrast;
brightness = brightness < 1 ? 1 : brightness;
brightness = brightness > 9 ? 9 : brightness;
float contrast_f = 1 + ((float)(contrast - 5)) / 10;
float brightness_f = 0 + ((float)(brightness - 5)) / 10;
string filters_descr = string.Format("eq=contrast=" + contrast_f.ToString() + ":brightness=" + brightness_f.ToString());
return init_filters(width, height, filters_descr);
}
}
public int Reset(int width, int height, int contrast, int brightness) {
Deinit();
return Init(width, height, contrast, brightness);
}
public int Filter(AVFrame * frame_src, AVFrame **frame_dst) {
lock (m_lock_record){
*frame_dst = frame_src;
if (m_filter_graph == null) {
return -1;
}
int ret;
//AV_BUFFERSRC_FLAG_KEEP_REF = 8,
ret = ffmpeg.av_buffersrc_add_frame_flags(m_buffersrc_ctx, frame_src, 8);
if (ret < 0)
return ret;
ret = ffmpeg.av_buffersink_get_frame(m_buffersink_ctx, m_filt_frame);
if (ret < 0)
return ret;
*frame_dst = m_filt_frame;
return 0;
}
}
public void UnrefFrame() {
lock (m_lock_record) {
if (m_filter_graph == null)
return ;
ffmpeg.av_frame_unref(m_filt_frame);
}
}
public void Deinit() {
if (m_filter_graph == null)
return ;
if(m_filter_graph != null) {
fixed(AVFilterGraph** filter_graph = &m_filter_graph)
ffmpeg.avfilter_graph_free(filter_graph);
}
if (m_filt_frame != null) {
fixed (AVFrame** filt_frame = &m_filt_frame)
ffmpeg.av_frame_free(filt_frame);
}
}
private int init_filters(int width, int height, string filters_descr) {
int ret = 0;
ffmpeg.avfilter_register_all();
//AVPixelFormat.AV_PIX_FMT_YUV420P = 0;
string args = string.Format("video_size=" + width.ToString() + "x" + height.ToString() + ":pix_fmt=0:time_base=1/20");
AVFilter* buffersrc = ffmpeg.avfilter_get_by_name("buffer");
AVFilter* buffersink = ffmpeg.avfilter_get_by_name("buffersink");
AVFilterInOut* outputs = ffmpeg.avfilter_inout_alloc();
AVFilterInOut* inputs = ffmpeg.avfilter_inout_alloc();
//AVRational time_base;
int* pix_fmts = (int*)ffmpeg.av_malloc(8);
pix_fmts[0] = (int)AVPixelFormat.AV_PIX_FMT_YUV420P;
pix_fmts[1] = (int)AVPixelFormat.AV_PIX_FMT_NONE;
//AVPixelFormat pix_fmts[] = { AVPixelFormat.AV_PIX_FMT_YUV420P, AVPixelFormat.AV_PIX_FMT_NONE };
m_filter_graph = ffmpeg.avfilter_graph_alloc();
if(outputs == null || inputs == null || m_filter_graph == null) {
ret = -1;
goto end;
}
fixed (AVFilterContext** buffersrc_ctx = &m_buffersrc_ctx) {
ret = ffmpeg.avfilter_graph_create_filter(buffersrc_ctx, buffersrc,"in", args, null, m_filter_graph);
if (ret < 0) {
goto end;
}
}
fixed (AVFilterContext** buffersink_ctx = &m_buffersink_ctx) {
ret = ffmpeg.avfilter_graph_create_filter(buffersink_ctx, buffersink,"out", null, null, m_filter_graph);
if (ret < 0){
goto end;
}
}
int size = (int)ffmpeg.av_int_list_length_for_size(1, (void*)pix_fmts, unchecked((ulong)AVPixelFormat.AV_PIX_FMT_NONE));
ret = ffmpeg.av_opt_set_bin(m_buffersink_ctx,"pix_fmts", (byte*)pix_fmts, size, ffmpeg.AV_OPT_SEARCH_CHILDREN);
if(ret < 0)
goto end;
outputs->name = ffmpeg.av_strdup("in");
outputs->filter_ctx = m_buffersrc_ctx;
outputs->pad_idx = 0;
outputs->next =null;
inputs->name = ffmpeg.av_strdup("out");
inputs->filter_ctx = m_buffersink_ctx;
inputs->pad_idx = 0;
inputs->next =null;
ret = ffmpeg.avfilter_graph_parse_ptr(m_filter_graph, filters_descr, &inputs, &outputs,null);
if (ret < 0)
goto end;
ret = ffmpeg.avfilter_graph_config(m_filter_graph,null);
if (ret < 0)
goto end;
m_filt_frame = ffmpeg.av_frame_alloc();
end:
ffmpeg.avfilter_inout_free(&inputs);
ffmpeg.avfilter_inout_free(&outputs);
ffmpeg.av_free(pix_fmts);
if (ret < 0)
Deinit();
return ret;
}
}
验证后有明显效果，可以根据自己的需求修改参数试试。
