FFMPEG官網給出了FFMPEG 濾鏡使用的執行個體，它是将視訊中的像素點替換成字元，然後從終端輸出。我在該執行個體的基礎上稍微的做了修改，使它能夠儲存濾鏡處理過後的檔案。在上代碼之前先明白幾個概念：
Filter:代表單個filter
FilterPad:代表一個filter的輸入或輸出端口，每個filter都可以有多個輸入和多個輸出，隻有輸出pad的filter稱為source,隻有輸入pad的filter稱為sink
FilterLink：若一個filter的輸出pad和另一個filter的輸入pad名字相同，即認為兩個filter之間建立了link
FilterChain:代表一串互相連接配接的filters，除了source和sink外，要求每個filter的輸入輸出pad都有對應的輸出和輸入pad
經典示例：
圖中的一系列操作共使用了四個filter，分别是
splite：将輸入的流進行分裂複制，分兩路輸出。
crop：根據給定的參數，對視訊進行裁剪
vflip：根據給定參數，對視訊進行翻轉等操作
overlay：将一路輸入覆寫到另一路之上，合并輸出為一路視訊
下面上代碼：
/*=============================================================================
# FileName: filter_video.c
# Desc: an example of ffmpeg fileter
# Author: licaibiao
# LastChange: 2017-03-16
=============================================================================*/
#define _XOPEN_SOURCE 600 /* for usleep */
#include <unistd.h>
#include "avcodec.h"
#include "avformat.h"
#include "avfiltergraph.h"
#include "buffersink.h"
#include "buffersrc.h"
#include "opt.h"
#define SAVE_FILE
const charchar *filter_descr = "scale=iw*2:ih*2";
static AVFormatContext *fmt_ctx;
static AVCodecContext *dec_ctx;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int video_stream_index = -1;
static int64_t last_pts = AV_NOPTS_VALUE;
static int open_input_file(const charchar *filename)
{
int ret;
AVCodec *dec;
if ((ret = avformat_open_input(&fmt_ctx, filename, NULL, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
return ret;
}
if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
/* select the video stream 判斷流是否正常 */
ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot find a video stream in the input file\n");
video_stream_index = ret;
dec_ctx = fmt_ctx->streams[video_stream_index]->codec;
av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0); /* refcounted_frames 幀引用計數 */
/* init the video decoder */
if ((ret = avcodec_open2(dec_ctx, dec, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open video decoder\n");
return 0;
}
static int init_filters(const charchar *filters_descr)
char args[512];
int ret = 0;
AVFilter *buffersrc = avfilter_get_by_name("buffer"); /* 輸入buffer filter */
AVFilter *buffersink = avfilter_get_by_name("buffersink"); /* 輸出buffer filter */
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base; /* 時間基數 */
#ifndef SAVE_FILE
enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_GRAY8, AV_PIX_FMT_NONE };
#else
enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
#endif
filter_graph = avfilter_graph_alloc(); /* 建立graph */
if (!outputs || !inputs || !filter_graph) {
ret = AVERROR(ENOMEM);
goto end;
/* buffer video source: the decoded frames from the decoder will be inserted here. */
snprintf(args, sizeof(args),
"video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
time_base.num, time_base.den,
dec_ctx->sample_aspect_ratio.num, dec_ctx->sample_aspect_ratio.den);
/* 建立并向FilterGraph中添加一個Filter */
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
/* buffer video sink: to terminate the filter chain. */
ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
NULL, NULL, filter_graph);
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
/* Set a binary option to an integer list. */
ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
/*
* Set the endpoints for the filter graph. The filter_graph will
* be linked to the graph described by filters_descr.
*/
* The buffer source output must be connected to the input pad of
* the first filter described by filters_descr; since the first
* filter input label is not specified, it is set to "in" by
* default.
outputs->name = av_strdup("in");
outputs->filter_ctx = buffersrc_ctx;
outputs->pad_idx = 0;
outputs->next = NULL;
* The buffer sink input must be connected to the output pad of
* the last filter described by filters_descr; since the last
* filter output label is not specified, it is set to "out" by
inputs->name = av_strdup("out");
inputs->filter_ctx = buffersink_ctx;
inputs->pad_idx = 0;
inputs->next = NULL;
/* Add a graph described by a string to a graph */
if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
&inputs, &outputs, NULL)) < 0)
/* Check validity and configure all the links and formats in the graph */
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
end:
avfilter_inout_free(&inputs);
avfilter_inout_free(&outputs);
return ret;
static void display_frame(const AVFrame *frame, AVRational time_base)
int x, y;
uint8_t *p0, *p;
int64_t delay;
if (frame->pts != AV_NOPTS_VALUE) {
if (last_pts != AV_NOPTS_VALUE) {
/* sleep roughly the right amount of time;
* usleep is in microseconds, just like AV_TIME_BASE. */
/* 計算 pts 是用來把時間戳從一個時基調整到另外一個時基時候用的函數 */
delay = av_rescale_q(frame->pts - last_pts,
time_base, AV_TIME_BASE_Q);
if (delay > 0 && delay < 1000000)
usleep(delay);
}
last_pts = frame->pts;
/* Trivial ASCII grayscale display. */
p0 = frame->data[0];
puts("\033c");
for (y = 0; y < frame->height; y++) {
p = p0;
for (x = 0; x < frame->width; x++)
putchar(" .-+#"[*(p++) / 52]);
putchar('\n');
p0 += frame->linesize[0];
fflush(stdout);
FILEFILE * file_fd;
static void write_frame(const AVFrame *frame)
static int printf_flag = 0;
if(!printf_flag){
printf_flag = 1;
printf("frame widht=%d,frame height=%d\n",frame->width,frame->height);
if(frame->format==AV_PIX_FMT_YUV420P){
printf("format is yuv420p\n");
else{
printf("formet is = %d \n",frame->format);
fwrite(frame->data[0],1,frame->width*frame->height,file_fd);
fwrite(frame->data[1],1,frame->width/2*frame->height/2,file_fd);
fwrite(frame->data[2],1,frame->width/2*frame->height/2,file_fd);
int main(int argc, charchar **argv)
AVPacket packet;
AVFrame *frame = av_frame_alloc();
AVFrame *filt_frame = av_frame_alloc();
int got_frame;
#ifdef SAVE_FILE
file_fd = fopen("test.yuv","wb+");
if (!frame || !filt_frame) {
perror("Could not allocate frame");
exit(1);
if (argc != 2) {
fprintf(stderr, "Usage: %s file\n", argv[0]);
av_register_all();
avfilter_register_all();
if ((ret = open_input_file(argv[1])) < 0)
if ((ret = init_filters(filter_descr)) < 0)
/* read all packets */
while (1) {
if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
break;
if (packet.stream_index == video_stream_index) {
got_frame = 0;
ret = avcodec_decode_video2(dec_ctx, frame, &got_frame, &packet);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error decoding video\n");
break;
}
if (got_frame) {
frame->pts = av_frame_get_best_effort_timestamp(frame); /* pts: Presentation Time Stamp */
/* push the decoded frame into the filtergraph */
if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
break;
}
/* pull filtered frames from the filtergraph */
while (1) {
ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
break;
if (ret < 0)
goto end;
display_frame(filt_frame, buffersink_ctx->inputs[0]->time_base);
write_frame(filt_frame);
av_frame_unref(filt_frame);
/* Unreference all the buffers referenced by frame and reset the frame fields. */
av_frame_unref(frame);
av_packet_unref(&packet);
avfilter_graph_free(&filter_graph);
avcodec_close(dec_ctx);
avformat_close_input(&fmt_ctx);
av_frame_free(&frame);
av_frame_free(&filt_frame);
if (ret < 0 && ret != AVERROR_EOF) {
fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
fclose(file_fd);
exit(0);
該工程中，我的Makefile檔案如下：
OUT_APP = test
INCLUDE_PATH = /usr/local/include/
INCLUDE = -I$(INCLUDE_PATH)libavutil/ -I$(INCLUDE_PATH)libavdevice/ \
-I$(INCLUDE_PATH)libavcodec/ -I$(INCLUDE_PATH)libswresample \
-I$(INCLUDE_PATH)libavfilter/ -I$(INCLUDE_PATH)libavformat \
-I$(INCLUDE_PATH)libswscale/
FFMPEG_LIBS = -lavformat -lavutil -lavdevice -lavcodec -lswresample -lavfilter -lswscale
SDL_LIBS =
LIBS = $(FFMPEG_LIBS)$(SDL_LIBS)
COMPILE_OPTS = $(INCLUDE)
C = c
OBJ = o
C_COMPILER = cc
C_FLAGS = $(COMPILE_OPTS) $(CPPFLAGS) $(CFLAGS)
LINK = cc -o
LINK_OPTS = -lz -lm -lpthread
LINK_OBJ = test.o
.$(C).$(OBJ):
$(C_COMPILER) -c $(C_FLAGS) $<
$(OUT_APP): $(LINK_OBJ)
$(LINK)$@ $(LINK_OBJ) $(LIBS) $(LINK_OPTS)
clean:
-rm -rf *.$(OBJ) $(OUT_APP) core *.core *~ *yuv
運作結果如下：
licaibiao@ubuntu:~/test/FFMPEG/filter$ ls
Makefile school.flv test test.c test.o
licaibiao@ubuntu:~/test/FFMPEG/filter$ ./test school.flv
[flv @ 0x12c16c0] video stream discovered after head already parsed
[flv @ 0x12c16c0] audio stream discovered after head already parsed
frame widht=1024,frame height=576
format is yuv420p
Makefile school.flv test test.c test.o test.yuv
在這裡，我列印出來了輸出視訊的格式和圖檔的長和寬，該執行個體生成的是一個YUV420 格式的視訊，使用YUV播放器播放視訊的時候，需要設定正确的視訊長度和寬度。在代碼中通過設定enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };來設定輸出格式。
過濾器的參數設定是通過const char *filter_descr = "scale=iw*2:ih*2"; 來設定。它表示将視訊的長和框都拉伸到原來的兩倍。具體的filter參數可以通過指令：ffmpeg -filters 來查詢。結果如下：
Filters:
T.. = Timeline support
.S. = Slice threading
..C = Command support
A = Audio input/output
V = Video input/output
N = Dynamic number and/or type of input/output
| = Source or sink filter
... abench A->A Benchmark part of a filtergraph.
... acompressor A->A Audio compressor.
... acrossfade AA->A Cross fade two input audio streams.
... acrusher A->A Reduce audio bit resolution.
.............................................................................
在上面的代碼中，我們設定的是将圖檔拉升到原來圖像的兩倍，其顯示效果如下，可能是截圖的問題，這裡看好像沒有拉伸到兩倍。
原圖
拉伸後
在上面的代碼中，我們設定的是：
const char *filter_descr = "scale=iw*2:ih*2"; iw 表示輸入視訊的寬，ih表示輸入視訊的高。可以任意比例的縮放視訊。這裡*2 表示放大兩倍,如果是/2表示縮小兩倍。
視訊縮放還可以直接設定：
const char *filter_descr = "scale=320:240"; 設定視訊輸出寬為320，高位240，當然也是可以随意的設定其他的參數。
視訊的裁剪可以設定為：
const char *filter_descr = "crop=320:240:0:0"; 具體含義是 crop=width:height:x:y，其中 width 和 height 表示裁剪後的尺寸，x:y 表示裁剪區域的左上角坐标。
視訊添加一個網格水印可以設定為：
const char *filter_descr = "drawgrid=width=100:height=100:thickness=2:[email protected]"; 具體含義是 width 和 height 表示添加網格的寬和高，thickness表示網格的線寬，color表示顔色 。其效果如下：