FFmpeg AVfilter应用例子

头文件
extern "C" {
#include "libavutil/mem.h"
#include "libavfilter/avfiltergraph.h"
#include "libavfilter/buffersink.h"
#include "libavfilter/buffersrc.h"
#include "libavutil/avutil.h"
#include "libavutil/imgutils.h"
#include "libavdevice/avdevice.h"
};

注册过滤器
avfilter_register_all();
/*
对pSrcFrame画框，最终图像数据保存在pDestFrame
*/
void VideoDecodec::DrawRectangleToFrame(AVFrame* pSrcFrame, AVFrame* pDestFrame, int x, int y, int w, int h)
{
AVFilterGraph* pFilterGraph = avfilter_graph_alloc();
char szErrMsg[128] = { 0 };
char szArgs[512] = { 0 };
char szFilterDescr[256] = { 0 };
sprintf(szFilterDescr, "drawbox=x=%d:y=%d:w=%d:h=%d:color=yellow@1", x, y, w, h);
AVFilter* pBufferSrc = avfilter_get_by_name("buffer");
AVFilter* pBufferSink = avfilter_get_by_name("buffersink");
AVFilterInOut* pFilterOut = avfilter_inout_alloc();
AVFilterInOut* pFilterIn = avfilter_inout_alloc();
enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUVJ420P, AV_PIX_FMT_NONE };
AVBufferSinkParams* pBufferSinkParams;

//最后的几个参数没有使用真实的视频格式参数
snprintf(szArgs, sizeof(szArgs), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
pSrcFrame->width, pSrcFrame->height, pSrcFrame->format, 1, 1, 1, 1);

int ret = 0;
AVFilterContext* pBufferSinkContext = NULL;
AVFilterContext* pBufferSrcContext = NULL;
if ((ret = avfilter_graph_create_filter(&pBufferSrcContext, pBufferSrc, "in", szArgs, NULL, pFilterGraph)) < 0)
{
  sprintf(szErrMsg, "Cannot graph create filter, error:%s\n", av_err2str(ret));
  return;
}
pBufferSinkParams = av_buffersink_params_alloc();
pBufferSinkParams->pixel_fmts = pix_fmts;
if ((ret = avfilter_graph_create_filter(&pBufferSinkContext, pBufferSink, "out", NULL, pBufferSinkParams, pFilterGraph)) < 0)
{
  sprintf(szErrMsg, "Cannot graph create filter, error:%s\n", av_err2str(ret));
  return;
}

pFilterOut->name = av_strdup("in");
pFilterOut->filter_ctx = pBufferSrcContext;
pFilterOut->pad_idx = 0;
pFilterOut->next = NULL;

pFilterIn->name = av_strdup("out");
pFilterIn->filter_ctx = pBufferSinkContext;
pFilterIn->pad_idx = 0;
pFilterIn->next = NULL;

do
{
  if ((ret = avfilter_graph_parse_ptr(pFilterGraph, szFilterDescr, &pFilterIn, &pFilterOut, NULL)) < 0)
  {
   sprintf(szErrMsg, "Cannot graph parse ptr, error:%s\n", av_err2str(ret));
   break;
  }

  if ((ret = avfilter_graph_config(pFilterGraph, NULL)) < 0)
  {
   sprintf(szErrMsg, "Cannot graph config filter, error:%s\n", av_err2str(ret));
   break;
  }

  if ((ret = av_buffersrc_add_frame(pBufferSrcContext, pSrcFrame)) < 0)
  {
   sprintf(szErrMsg, "Cannot add frame from buffersrc, error:%s\n", av_err2str(ret));
   break;
  }
  //pDestFrame帧的长宽必须指定
  //图像格式转换之后，pSrcFrame中的data数据被置为NULL,pSrcFrame结构不可用
  if ((ret = av_buffersink_get_frame(pBufferSinkContext, pDestFrame)) < 0)
  {
   sprintf(szErrMsg, "Cannot get frame frome buffersink, error:%s\n", av_err2str(ret));
   break;
  }
} while (0);

avfilter_inout_free(&pFilterIn);
avfilter_inout_free(&pFilterOut);
av_free(pBufferSinkParams);
avfilter_graph_free(&pFilterGraph);
}

注意

1.调用avfilter_get_by_name("ffbuffersink")时在新版本3.4的ffmpeg要修改为avfilter_get_by_name("buffersink");否则返回指针为空，调用avfilter_graph_create_filter返回-12

FFmpeg AVfilter应用例子

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