FFMPEG学习----使用SDL构建视频播放器

时间:2020-12-10 12:06:23
#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;
AVPacketpacket;
struct SwsContext*img_convert_ctx = NULL;
inty_size;
intgot_picture;
inti, videoIndex;
intframe_cnt = 1;

//------------SDL----------------
SDL_Window*sdlScreen = NULL;
SDL_Renderer*sdlRenderer = NULL;
SDL_Texture*sdlTexture = NULL;
SDL_RectsdlRect;
SDL_Thread*sdlThread = NULL;
SDL_Eventevent;


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;
}



FFMPEG学习----使用SDL构建视频播放器

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。

FFMPEG学习----使用SDL构建视频播放器