#Filter和SDL（Video）
本文主要来自官方例子doc/examples/filtering_video.c 。
- 滤镜官方语法 , 推荐参考《FFmpeg从入门到精通》。
##使用滤镜流程
其中，AVFormatContext、AVPacket等重要的结构体请看：FFmpeg重要结构体 。
##代码实现
/**
* @author 秦城季
* @email xhunmon@126.com
* @Blog https://qincji.gitee.io
* @date 2021/01/09
* description: 来自官方例子：doc/examples/filtering_video.c
* <br>
*/
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#define _XOPEN_SOURCE 600 /* for usleep */
#include <unistd.h>
extern "C" {
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/opt.h>
#include <SDL.h>
};
//swapuv
//const char *filter_descr = "scale=78:24,transpose=cclock";
//const char *filter_descr = "movie=logo.png[wm];[in][wm]overlay=30:10[out]";
const char *filter_descr = "scale=iw/2:ih/2[in_tmp];[in_tmp]split=4[in_1][in_2][in_3][in_4];[in_1]pad=iw*2:ih*2[a];[a][in_2]overlay=w[b];[b][in_3]overlay=0:h[d];[d][in_4]overlay=w:h[out]";
/* other way:
scale=78:24 [scl]; [scl] transpose=cclock // assumes "[in]" and "[out]" to be input output pads respectively
*/
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 char *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");
return ret;
}
/* select the video stream */
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");
return ret;
}
video_stream_index = ret;
/* create decoding context */
dec_ctx = avcodec_alloc_context3(dec);
if (!dec_ctx)
return AVERROR(ENOMEM);
avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[video_stream_index]->codecpar);
/* 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 ret;
}
return 0;
}
static int init_filters(const char *filters_descr) {
char args[512];
int ret = 0;
const AVFilter *buffersrc = avfilter_get_by_name("buffer");//预缓存帧数据。用于输入
const AVFilter *buffersink = avfilter_get_by_name("buffersink");//缓冲视频帧，并使它们可用于过滤器图形的末尾。用于输出
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base;
enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE};//注意输入的格式类型pix_fmts[0]
filter_graph = avfilter_graph_alloc();
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);
//创建和初始化过滤器实例并将其添加到现有图形中。【输入】
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
goto end;
}
//创建和初始化过滤器实例并将其添加到现有图形中。【输出】
/* buffer video sink: to terminate the filter chain. */
ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
NULL, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
goto end;
}
//给buffersink_ctx设置参数
ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,
AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
goto end;
}
/*
* 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
* default.
*/
inputs->name = av_strdup("out");
inputs->filter_ctx = buffersink_ctx;
inputs->pad_idx = 0;
inputs->next = NULL;
//将字符串描述的图形添加到图形中。
if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
&inputs, &outputs, NULL)) < 0){
av_log(NULL, AV_LOG_ERROR, "Error avfilter_graph_parse_ptr\n");
goto end;
}
//检查AVFilterGraph有效性
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0){
av_log(NULL, AV_LOG_ERROR, "Error avfilter_graph_config\n");
goto end;
}
end:
avfilter_inout_free(&inputs);
avfilter_inout_free(&outputs);
return ret;
}
static SDL_Renderer *sdl_renderer;
static SDL_Texture *sdl_texture;
static SDL_Rect sdl_rect;
static int init_sdl(AVCodecContext *dec_ctx) {
int ret = -1;
SDL_Window *screen;
// B1. 初始化SDL子系统：缺省(事件处理、文件IO、线程)、视频、音频、定时器
if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)){
printf("SDL_Init() failed: %s\n", SDL_GetError());
goto end;
}
// B2. 创建SDL窗口，SDL 2.0支持多窗口
// SDL_Window即运行程序后弹出的视频窗口，同SDL 1.x中的SDL_Surface
screen = SDL_CreateWindow("Simplest ffmpeg player's Window",
SDL_WINDOWPOS_UNDEFINED,// 不关心窗口X坐标
SDL_WINDOWPOS_UNDEFINED,// 不关心窗口Y坐标
dec_ctx->width,
dec_ctx->height,
SDL_WINDOW_OPENGL
);
if (!screen){
printf("SDL_CreateWindow() failed: %s\n", SDL_GetError());
goto end;
}
// B3. 创建SDL_Renderer
// SDL_Renderer：渲染器
sdl_renderer = SDL_CreateRenderer(screen, -1, 0);
// B4. 创建SDL_Texture
// 一个SDL_Texture对应一帧YUV数据，同SDL 1.x中的SDL_Overlay
// 此处第2个参数使用的是SDL中的像素格式，对比参考注释A7
// FFmpeg中的像素格式AV_PIX_FMT_YUV420P对应SDL中的像素格式SDL_PIXELFORMAT_IYUV
sdl_texture = SDL_CreateTexture(sdl_renderer,
SDL_PIXELFORMAT_IYUV,
SDL_TEXTUREACCESS_STREAMING,
dec_ctx->width,
dec_ctx->height);
sdl_rect.x = 0;
sdl_rect.y = 0;
sdl_rect.w = dec_ctx->width;
sdl_rect.h = dec_ctx->height;
ret = 1;
end:
return ret;
}
static void sdl_play(const AVFrame *frame){
// B5. 使用新的YUV像素数据更新SDL_Rect
SDL_UpdateYUVTexture(sdl_texture, // sdl texture
&sdl_rect, // sdl rect &sdl_rect
frame->data[0], // y plane
frame->linesize[0], // y pitch
frame->data[1], // u plane
frame->linesize[1], // u pitch
frame->data[2], // v plane
frame->linesize[2] // v pitch
);
// B6. 使用特定颜色清空当前渲染目标
SDL_RenderClear(sdl_renderer);
// B7. 使用部分图像数据(texture)更新当前渲染目标
SDL_RenderCopy(sdl_renderer, // sdl renderer
sdl_texture, // sdl texture
NULL, // src rect, if NULL copy texture
&sdl_rect // dst rect
);
// B8. 执行渲染，更新屏幕显示
SDL_RenderPresent(sdl_renderer);
// B9. 控制帧率为25FPS，此处不够准确，未考虑解码消耗的时间
//Delay 40ms
SDL_Event e;
while (SDL_PollEvent(&e)) {
SDL_Delay(40);
if (e.type == SDL_QUIT) {
break;
}
}
}
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. */
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;
}
sdl_play(frame);
/* 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);*/
}
int main(int argc, char **argv) {
int ret;
AVPacket packet;
AVFrame *frame;
AVFrame *filt_frame;
const char *filename = "source/Kobe.flv";
// const char *filename = "source/lol.mp4";
frame = av_frame_alloc();
filt_frame = av_frame_alloc();
if (!frame || !filt_frame) {
perror("Could not allocate frame");
exit(1);
}
//获取解封装上下文（AVFormatContext）和解码器，并查找视频通道
if ((ret = open_input_file(filename)) < 0)
goto end;
//这是本节的重点：滤镜器的使用
if ((ret = init_filters(filter_descr)) < 0)
goto end;
//用来显示播放结果
if ((ret = init_sdl(dec_ctx)) < 0)
goto end;
/* read all packets */
while (1) {
if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
break;
if (packet.stream_index == video_stream_index) {
//送去解码
ret = avcodec_send_packet(dec_ctx, &packet);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
break;
}
while (ret >= 0) {
//获取解码后数据
ret = avcodec_receive_frame(dec_ctx, frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
break;
} else if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
goto end;
}
frame->pts = frame->best_effort_timestamp;
/**将解码后得到的数据通过滤镜处理*/
/* 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) {
/**得到滤镜处理后的数据*/
ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
break;
if (ret < 0)
goto end;
//将得到滤镜处理后的数据进行处理，播放、重新封装、转格式或者直接保存到文件等
display_frame(filt_frame, buffersink_ctx->inputs[0]->time_base);
av_frame_unref(filt_frame);
}
av_frame_unref(frame);
}
}
av_packet_unref(&packet);
}
end:
SDL_Quit();
avfilter_graph_free(&filter_graph);
avcodec_free_context(&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));
exit(1);
}
exit(0);
}cmake_minimum_required(VERSION 3.17)
project(VAFFmpeg)
set(CMAKE_CXX_STANDARD 11)
set(SOURCE_FILES main.cpp)
link_directories(lib)
include_directories(include)
#引入sdl2库
find_package(SDL2 REQUIRED)
include_directories(VAFFmpeg ${SDL2_INCLUDE_DIRS})
add_executable(VAFFmpeg ${SOURCE_FILES})
target_link_libraries(
VAFFmpeg
${SDL2_LIBRARIES}
-lavcodec
-lavdevice
-lavfilter
-lavformat
-lswresample
-lswscale
# -lx264
)##测试文件下载地址
参考