sdl2.0示例

// gcc -o testDrone2_video testDrone2_video.c -lavcodec -lavformat -lswscale -lSDL2
// g++ -o testDrone2_video testDrone2_video.c -lavcodec -lavformat -lswscale -lSDL2

#ifdef __cplusplus
extern "C" {
#endif

#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"

#ifdef __cplusplus
}
#endif

#include "SDL2/SDL.h"

int main(int argc, char* argv[]) {

// 3.0. Initializes the video subsystem *must be done before anything other!!
if (SDL_Init(SDL_INIT_VIDEO) < 0) {
fprintf(stderr, "Unable to init SDL: %s\n", SDL_GetError());
return -1;
}

// prepare variables
// decoding
char *drone_addr = "http://192.168.1.1:5555";
AVFormatContext *pFormatCtx = NULL;
AVCodecContext *pCodecCtx;
AVCodec *pCodec;
AVPacket packet;
AVFrame *pFrame;
int terminate, frameDecoded;

// converting
AVFrame *pFrame_YUV420P;
uint8_t *buffer_YUV420P;
struct SwsContext *pConvertCtx_YUV420P;

AVFrame *pFrame_BGR24;
uint8_t *buffer_BGR24;
struct SwsContext *pConvertCtx_BGR24;

// displaying
SDL_Window *pWindow1;
SDL_Renderer *pRenderer1;
SDL_Texture *bmpTex1;
uint8_t *pixels1;
int pitch1, size1;

SDL_Window *pWindow2;
SDL_Renderer *pRenderer2;
SDL_Texture *bmpTex2;
uint8_t *pixels2;
int pitch2, size2;

// SDL event handling
SDL_Event event;

// 1.1 Register all formats and codecs
av_register_all();
avcodec_register_all();
avformat_network_init();

// 1.2. Open video file
while(avformat_open_input(&pFormatCtx, drone_addr, NULL, NULL) != 0)
printf("Could not open the video file\nRetrying...\n");

// 1.3. Retrieve stream information
avformat_find_stream_info(pFormatCtx, NULL);
// Dump information about file to standard output
av_dump_format(pFormatCtx, 0, drone_addr, 0);

// 1.4. Get a pointer to the codec context for the video stream
// and find the decoder for the video stream
pCodecCtx = pFormatCtx->streams[0]->codec;
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);

// 1.5. Open Codec
avcodec_open2(pCodecCtx, pCodec, NULL);


// 2.1.1. Prepare format conversion for diplaying with SDL
// Allocate an AVFrame structure
pFrame_YUV420P = avcodec_alloc_frame();
if(pFrame_YUV420P == NULL) {
fprintf(stderr, "Could not allocate pFrame_YUV420P\n");
return -1;
}
// Determine required buffer size and allocate buffer
buffer_YUV420P = (uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P,
pCodecCtx->width, pCodecCtx->height));
// Assign buffer to image planes
avpicture_fill((AVPicture *)pFrame_YUV420P, buffer_YUV420P,
PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
// format conversion context
pConvertCtx_YUV420P = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P,
SWS_SPLINE, NULL, NULL, NULL);

// 2.2.1. Prepare format conversion for OpenCV
// Allocate an AVFrame structure
pFrame_BGR24 = avcodec_alloc_frame();
if(pFrame_BGR24 == NULL) {
fprintf(stderr, "Could not allocate pFrame_YUV420P\n");
return -1;
}
// Determine required buffer size and allocate buffer
buffer_BGR24 = (uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_BGR24,
pCodecCtx->width, pCodecCtx->height));
// Assign buffer to image planes
avpicture_fill((AVPicture *)pFrame_BGR24, buffer_BGR24,
PIX_FMT_BGR24, pCodecCtx->width, pCodecCtx->height);
// format conversion context
pConvertCtx_BGR24 = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height, PIX_FMT_BGR24,
SWS_SPLINE, NULL, NULL, NULL);

// 3.1.1 prepare SDL for YUV
// allocate window, renderer, texture
pWindow1 = SDL_CreateWindow( "YUV", 0, 0, pCodecCtx->width, pCodecCtx->height, SDL_WINDOW_SHOWN);
pRenderer1 = SDL_CreateRenderer(pWindow1, -1, SDL_RENDERER_ACCELERATED);
bmpTex1 = SDL_CreateTexture(pRenderer1, SDL_PIXELFORMAT_YV12, SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height);
size1 = pCodecCtx->width * pCodecCtx->height;
if(pWindow1==NULL | pRenderer1==NULL | bmpTex1==NULL) {
fprintf(stderr, "Could not open window1\n%s\n", SDL_GetError());
return -1;
}

// 3.2.1 prepare SDL for BGR
// allocate window, renderer, texture
pWindow2 = SDL_CreateWindow( "BGR", pCodecCtx->width+5, 0, pCodecCtx->width, pCodecCtx->height, SDL_WINDOW_SHOWN);
pRenderer2 = SDL_CreateRenderer(pWindow2, -1, SDL_RENDERER_ACCELERATED);
bmpTex2 = SDL_CreateTexture(pRenderer2, SDL_PIXELFORMAT_BGR24, SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height);
size2 = pCodecCtx->width * pCodecCtx->height * 3;
if(pWindow2==NULL | pRenderer2==NULL | bmpTex2==NULL) {
fprintf(stderr, "Could not open window2\n%s\n", SDL_GetError());
return -1;
}

// 1.6. get video frames
pFrame = avcodec_alloc_frame();
terminate = 0;
while(!terminate) {
// read frame
if(av_read_frame(pFormatCtx, &packet)<0) {
fprintf(stderr, "Could not read frame!\n");
continue;
}

// decode the frame
if(avcodec_decode_video2(pCodecCtx, pFrame, &frameDecoded, &packet) < 0) {
fprintf(stderr, "Could not decode frame!\n");
continue;
}

if (frameDecoded) {
// 2.1.2. convert frame to YUV for Displaying
sws_scale(pConvertCtx_YUV420P, (const uint8_t * const*)pFrame->data, pFrame->linesize, 0,
pCodecCtx->height, pFrame_YUV420P->data, pFrame_YUV420P->linesize);
// 2.2.2. convert frame to GRAYSCALE [or BGR] for OpenCV
sws_scale(pConvertCtx_BGR24, (const uint8_t * const*)pFrame->data, pFrame->linesize, 0,
pCodecCtx->height, pFrame_BGR24->data, pFrame_BGR24->linesize);

// 3.1.2. copy converted YUV to SDL 2.0 texture
SDL_LockTexture(bmpTex1, NULL, (void **)&pixels1, &pitch1);
memcpy(pixels1, pFrame_YUV420P->data[0], size1 );
memcpy(pixels1 + size1, pFrame_YUV420P->data[2], size1/4);
memcpy(pixels1 + size1*5/4, pFrame_YUV420P->data[1], size1/4);
SDL_UnlockTexture(bmpTex1);
SDL_UpdateTexture(bmpTex1, NULL, pixels1, pitch1);
// refresh screen
SDL_RenderClear(pRenderer1);
SDL_RenderCopy(pRenderer1, bmpTex1, NULL, NULL);
SDL_RenderPresent(pRenderer1);

// 3.2.2. copy converted BGR to SDL 2.0 texture
SDL_LockTexture(bmpTex2, NULL, (void **)&pixels2, &pitch2);
memcpy(pixels2, pFrame_BGR24->data[0], size2);
SDL_UnlockTexture(bmpTex2);
SDL_UpdateTexture(bmpTex2, NULL, pixels2, pitch2);
// refresh screen
SDL_RenderClear(pRenderer2);
SDL_RenderCopy(pRenderer2, bmpTex2, NULL, NULL);
SDL_RenderPresent(pRenderer2);
}

SDL_PollEvent(&event);
switch (event.type) {
case SDL_KEYDOWN:
terminate = 1;
break;
}
}

// release
// *note SDL objects have to be freed before closing avcodec.
// otherwise it causes segmentation fault for some reason.
SDL_DestroyTexture(bmpTex1);
SDL_DestroyTexture(bmpTex2);

SDL_DestroyRenderer(pRenderer1);
SDL_DestroyRenderer(pRenderer2);

SDL_DestroyWindow(pWindow1);
SDL_DestroyWindow(pWindow2);

av_free(pFrame_YUV420P);
av_free(buffer_YUV420P);
sws_freeContext(pConvertCtx_YUV420P);

av_free(pFrame_BGR24);
av_free(buffer_BGR24);
sws_freeContext(pConvertCtx_BGR24);

av_free(pFrame);
avcodec_close(pCodecCtx); // <- before freeing this, all other objects, allocated after this, must be freed
avformat_close_input(&pFormatCtx);

SDL_Quit();

return 0;

}

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sdl2.0示例

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