FFmpeg AVfilter應用例子

頭文件
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"
};

注冊過濾器
?avfilter_register_all();
/*
對pSrcFrame畫框，最終圖像數(shù)據(jù)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;

?//最后的幾個參數(shù)沒有使用真實的視頻格式參數(shù)
?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幀的長寬必須指定
??//圖像格式轉換之后，pSrcFrame中的data數(shù)據(jù)被置為NULL,pSrcFrame結構不可用
??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.調用avfilter_get_by_name("ffbuffersink")時在新版本3.4的ffmpeg要修改為avfilter_get_by_name("buffersink");否則返回指針為空，調用avfilter_graph_create_filter返回-12