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。

巴特西

FFMPEG学习----使用SDL构建视频播放器

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