FFMPEG学习----使用SDL构建视频播放器
#include <stdio.h>
#include <string.h>
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "libavutil/imgutils.h"
#include "SDL.h"
};
//依赖库
#pragma comment(lib, "avcodec.lib")
#pragma comment(lib, "avformat.lib")
#pragma comment(lib, "swscale.lib")
#pragma comment(lib, "avutil.lib")
#pragma comment(lib, "SDL2.lib")
#pragma comment(lib, "SDL2main.lib")
//Refresh Event
#define REFRESH_EVENT (SDL_USEREVENT + 1)
//Break Event
#define BREAK_EVENT (SDL_USEREVENT + 2)
bool thread_exit = false;
bool thread_pause = false;
int RefreshVideo(void *opaque)
{
thread_exit = false;
thread_pause = false;
while (!thread_exit)
{
//没按 space
if (!thread_pause)
{
SDL_Event event;
event.type = REFRESH_EVENT;
SDL_PushEvent(&event);
}
SDL_Delay(40);
}
thread_exit = false;
thread_pause = false;
//Break 退出main函数循环
SDL_Event event;
event.type = BREAK_EVENT;
SDL_PushEvent(&event);
return 0;
}
int main(int argc, char* argv[])
{
//------------FFmpeg----------------
AVFormatContext *pFormatCtx = NULL;
AVCodecContext *pCodecCtx = NULL;
AVCodec *pCodec = NULL;
AVFrame *pFrame = NULL, *pFrameYUV = NULL;
unsigned char *out_buffer = NULL;
AVPacket packet;
struct SwsContext *img_convert_ctx = NULL;
int y_size;
int got_picture;
int i, videoIndex;
int frame_cnt = 1;
//------------SDL----------------
SDL_Window *sdlScreen = NULL;
SDL_Renderer *sdlRenderer = NULL;
SDL_Texture *sdlTexture = NULL;
SDL_Rect sdlRect;
SDL_Thread *sdlThread = NULL;
SDL_Event event;
char filepath[1024] = "";
printf("Usage: program.exe Titanic.ts\n");
if (argc == 2)
{
strcpy(filepath, argv[1]);
}
else
{
printf("Could not find a file\n");
return -1;
}
av_register_all();
if (avformat_open_input(&pFormatCtx, filepath, NULL, NULL) != 0)
{
printf("Couldn't open an input stream.\n");
return -1;
}
if (avformat_find_stream_info(pFormatCtx, NULL) < 0)
{
printf("Couldn't find stream information.\n");
return -1;
}
videoIndex = -1;
for (i = 0; i < pFormatCtx->nb_streams; i++)
if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
{
videoIndex = i;
break;
}
if (videoIndex == -1)
{
printf("Couldn't find a video stream.\n");
return -1;
}
pCodecCtx = pFormatCtx->streams[videoIndex]->codec;
pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
if (pCodec == NULL)
{
printf("Codec not found.\n");
return -1;
}
if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
{
printf("Could not open codec.\n");
return -1;
}
//Output Info-----------------------------
printf("--------------- File Information ----------------\n");
av_dump_format(pFormatCtx, 0, filepath, 0);
printf("-------------------------------------------------\n");
pFrame = av_frame_alloc();
pFrameYUV = av_frame_alloc();
if (pFrame == NULL || pFrameYUV == NULL)
{
printf("memory allocation error\n");
return -1;
}
out_buffer = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1));
av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize, out_buffer,
AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height, 1);
img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
if (SDL_Init(SDL_INIT_VIDEO))
{
printf("Could not initialize SDL - %s\n", SDL_GetError());
return -1;
}
sdlScreen = SDL_CreateWindow("FFmpeg Player",
SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
pCodecCtx->width, pCodecCtx->height, SDL_WINDOW_OPENGL);
if (sdlScreen == 0)
{
printf("SDL: could not create SDL_Window - exiting:%s\n", SDL_GetError());
return -1;
}
sdlRenderer = SDL_CreateRenderer(sdlScreen, -1, SDL_RENDERER_ACCELERATED);
if (sdlRenderer == NULL)
{
printf("SDL: could not create SDL_Renderer - exiting:%s\n", SDL_GetError());
return -1;
}
sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height);
if (sdlTexture == NULL)
{
printf("SDL: could not create SDL_Texture - exiting:%s\n", SDL_GetError());
return -1;
}
//设置图像显示位置
sdlRect.x = 10;
sdlRect.y = 10;
sdlRect.w = pCodecCtx->width - 20;
sdlRect.h = pCodecCtx->height - 20;
sdlThread = SDL_CreateThread(RefreshVideo, NULL, NULL);
while (true)
{
SDL_WaitEvent(&event);
if (event.type == REFRESH_EVENT)
{
while (true)
{
if (av_read_frame(pFormatCtx, &packet) < 0)
{
thread_exit = true;
}
if (packet.stream_index == videoIndex)
{
break;
}
}
if (avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, &packet) < 0)
{
printf("Decode Error.\n");
return -1;
}
if (got_picture)
{
sws_scale(img_convert_ctx, (const unsigned char* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height,
pFrameYUV->data, pFrameYUV->linesize);
SDL_UpdateYUVTexture(sdlTexture, NULL,
pFrameYUV->data[0], pFrameYUV->linesize[0],
pFrameYUV->data[1], pFrameYUV->linesize[1],
pFrameYUV->data[2], pFrameYUV->linesize[2]
);
//SDL_UpdateTexture(sdlTexture, NULL, pFrameYUV->data[0], pFrameYUV->linesize[0]);
SDL_RenderClear(sdlRenderer);
SDL_RenderCopy(sdlRenderer, sdlTexture, NULL, &sdlRect);
SDL_RenderPresent(sdlRenderer);
printf("Succeed to decode %d frame!\n", frame_cnt);
frame_cnt++;
}
av_free_packet(&packet);
}
else if (event.type == SDL_KEYDOWN)
{
//pause
if (event.key.keysym.sym == SDLK_SPACE)
{
thread_pause = !thread_pause;
}
}
else if (event.type == SDL_QUIT)
{
thread_exit = true;
}
else if (event.type == BREAK_EVENT)
{
break;
}
}//while
SDL_Quit();
sws_freeContext(img_convert_ctx);
av_frame_free(&pFrameYUV);
av_frame_free(&pFrame);
avcodec_close(pCodecCtx);
avformat_close_input(&pFormatCtx);
return 0;
}
有人会疑惑，为什么解码后的pFrame不直接用于显示，而是调用swscale()转换之后进行显示？
如果不进行转换，而是直接调用SDL进行显示的话，会发现显示出来的图像是混乱的。关键问题在于解码后的pFrame的linesize里存储的不是图像的宽度，而是比宽度大一些的一个值。其原因目前还没有仔细调查（大概是出于性能的考虑）。例如分辨率为480x272的图像，解码后的视频的linesize[0]为512，而不是480。以第1行亮度像素（pFrame->data[0]）为例，从0-480存储的是亮度数据，而从480-512则存储的是无效的数据。因此需要使用swscale()进行转换。转换后去除了无效数据，linesize[0]变为480。就可以正常显示了。
Keep it simple!
