ffmpeg学习---2Outputting to the Screen

1. 2output.c

// tutorial01.c
// Code based on a tutorial by Martin Bohme ([e-mail])
// Tested on Gentoo, CVS version 5/01/07 compiled with GCC 4.1.1

// A small sample program that shows how to use libavformat and libavcodec to
// read video from a file.
//
// Use
//
// gcc -o tutorial01 tutorial01.c -lavformat -lavcodec -lz
//
// to build (assuming libavformat and libavcodec are correctly installed
// your system).
//
// Run using
//
// tutorial01 myvideofile.mpg
//
// to write the first five frames from "myvideofile.mpg" to disk in PPM
// format.
#include <stdio.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <SDL.h>
int main(int argc, char *argv[]) {
    AVFormatContext *pFormatCtx;
    int i, videoStream;
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame;
    AVFrame *pFrameRGB;
    AVPacket        packet;
    int frameFinished;
    int numBytes;
    uint8_t *buffer;

    if(argc < 2) {
        printf("Please provide a movie file\n");
        return -1;
    }

    if(SDL_Init(SDL_INIT_VIDEO|SDL_INIT_AUDIO|SDL_INIT_TIMER))
    {
        fprintf(stderr, "SD_init error \n");
        exit(1);
    }
    // Register all formats and codecs
    av_register_all();

    pFormatCtx = avformat_alloc_context();

    // Open video file
    //if(av_open_input_file(&pFormatCtx, argv[1], NULL, 0, NULL)!=0)
    if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
        return -1; // Couldn't open file

    // Retrieve stream information
    if(avformat_find_stream_info(pFormatCtx,NULL)<0)
        return -1; // Couldn't find stream information

    // Dump information about file onto standard error
    av_dump_format(pFormatCtx, 0, argv[1], 0);

    // Find the first video stream
    videoStream=-1;
    for(i=0; i<pFormatCtx->nb_streams; i++)
        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
        {
            videoStream=i;
            break;
        }
    if(videoStream==-1)
        return -1; // Didn't find a video stream

    // Get a pointer to the codec context for the video stream
    pCodecCtx=pFormatCtx->streams[videoStream]->codec;

    // Find the decoder for the video stream
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
    if(pCodec==NULL) {
        fprintf(stderr, "Unsupported codec!\n");
        return -1; // Codec not found
    }

    // Open codec
    if(avcodec_open2(pCodecCtx, pCodec, NULL)<0)
        return -1; // Could not open codec

    //Set up a screen
    SDL_Surface * screen;
    screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
    if(!screen)
    {
        fprintf(stderr, "SetVideoMode error\n");
        exit(1);
    }

    //create a YUV overlay
    SDL_Overlay *bmp;
    SDL_Rect rect;
    SDL_Event  event;
    bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height,
            SDL_YV12_OVERLAY, screen);
    // Allocate video frame
    pFrame=avcodec_alloc_frame();

    // Allocate an AVFrame structure
    pFrameRGB=avcodec_alloc_frame();
    if(pFrameRGB==NULL)
        return -1;

    // Determine required buffer size and allocate buffer
    numBytes=avpicture_get_size(PIX_FMT_RGB24, pCodecCtx->width,
            pCodecCtx->height);
    buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));

    // Assign appropriate parts of buffer to image planes in pFrameRGB
    // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
    // of AVPicture
    avpicture_fill((AVPicture *)pFrameRGB, buffer, PIX_FMT_RGB24,
            pCodecCtx->width, pCodecCtx->height);

    // Read frames and display on screen
    while(av_read_frame(pFormatCtx, &packet)>=0) {
        // Is this a packet from the video stream?
        if(packet.stream_index==videoStream) {
            // Decode video frame
            avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);

            // Did we get a video frame?
            if(frameFinished) {
                SDL_LockYUVOverlay(bmp);
                AVPicture pict;
                pict.data[0] = bmp->pixels[0];
                pict.data[1] = bmp->pixels[2];
                pict.data[2] = bmp->pixels[1];

                pict.linesize[0] = bmp->pitches[0];
                pict.linesize[1] = bmp->pitches[2];
                pict.linesize[2] = bmp->pitches[1];

               // img_convert(&pict, PIX_FMT_YUV420P, (AVPicture*)pFrame, pCodecCtx->pix_fmt,
               // pCodecCtx->width, pCodecCtx->height);
                struct SwsContext *img_convert_ctx;
                img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
                if(img_convert_ctx == NULL)
                {
                    fprintf(stderr, "Cannot initialize the conversion context!\n");
                            exit(1);
                }

                sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize);
                SDL_UnlockYUVOverlay(bmp);
                rect.x = 0;
                rect.y = 0;
                rect.w = pCodecCtx->width;
                rect.h = pCodecCtx->height;
                SDL_DisplayYUVOverlay(bmp, &rect);

            }
        }

        // Free the packet that was allocated by av_read_frame
        av_free_packet(&packet);
        SDL_PollEvent(&event);
        switch(event.type)
        {
            case SDL_QUIT:
                SDL_Quit();
                exit(0);
                break;
            default:
                break;
        }
    }

    // Free the RGB image
    av_free(buffer);
    av_free(pFrameRGB);

    // Free the YUV frame
    av_free(pFrame);

    // Close the codec
    avcodec_close(pCodecCtx);

    // Close the video file
    avformat_close_input(&pFormatCtx);

    return 0;
}

2.Makefile

CC=gcc
CFLAGS = -g -I/home/sun/code/ffmpeg-1.0/install/include/ -I/home/sun/code/SDL-1.2.15/install/include/SDL/
LDFLAGS = -L/home/sun/code/ffmpeg-1.0/install/lib/ -lavutil -lavformat -lavcodec -lavutil -lm -lswscale
LDFLAGS += -L/home/sun/code/SDL-1.2.15/install/lib/ -lSDLmain -lSDL

TARGETS=2output
all: $(TARGETS)
2output.o:2output.c
    $(CC) $(CFLAGS) -o $@ -c $^

2output:2output.o
    $(CC) -o $@ $^ $(LDFLAGS)
clean:
    rm -rf *.o  $(TARGETS)

---

二. 更新版
1. 代码
现在ffmpeg发布了ffmpeg-2.7.2,下面基于这个版本更新一下,同时加上注解,下次看的时候理解就更深了

cong@msi:/work/ffmpeg/test/1view$ cat view.c
#include "utils.h"
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <SDL/SDL.h>

SDL_mutex *affmutex;
SDL_Event sdlevent;
int signal_quit = 1;

static int eventThread(void* data)
{
    while(signal_quit)
    {
        SDL_LockMutex(affmutex);
        while(SDL_PollEvent(&sdlevent))
        {
            switch(sdlevent.type)
            {
                case SDL_QUIT:
                    {
                        signal_quit = 0;
                    }
                    break;
                default:
                    break;

            }
        }
        SDL_UnlockMutex(affmutex);
    }
}

int main(int argc, char **argv)
{
    int i=0;
    int ret;
    int videoindex= -1;
    int frameFinished;
    AVFormatContext *pFormatCtx = NULL;
    AVCodecContext * pCodecCtx;
    AVCodec * pCodec;
    AVFrame * pFrame;
    AVFrame * pFrameYUV;
    AVPacket * packet;
    struct SwsContext *img_convert_ctx;

    SDL_Surface* psscreen;
    SDL_Overlay* overlay;
    SDL_Rect     rect;
    SDL_Thread* sdl_thread;
    //a. ffmpeg的初始化(虽然名字是register就这么说吧)
    avcodec_register_all();
    avfilter_register_all();
    av_register_all();

    //b.打开视频文件
    pFormatCtx = avformat_alloc_context();
    if(avformat_open_input(&pFormatCtx, argv[1], NULL, NULL)!=0)
        return -1;
    //c.获取视频文件的流信息,(即查看有几个视频流几个音频流)
    if(avformat_find_stream_info(pFormatCtx, NULL)<0)
        return -1;
    av_dump_format(pFormatCtx,0, 0, 0);
    //d.获取了视频流的index,这样以后读取一帧之后,根据索引号才能判断这一帧是不是视频帧
    for(i=0; i<pFormatCtx->nb_streams; i++)
    {
        if(pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
        {
            videoindex= i;
            break;
        }
    }
    if(videoindex== -1)
    {
        dbmsg("no video stream found!");
        return -1;
    }
    dbmsg("videoindex=%d", videoindex);
    //e.为视频流寻找解码器:在c中不仅有视频流的index,还有视频流的编码codec_id
    //通过这个codec_id就可以寻到视频流的解码器
    pCodecCtx = pFormatCtx->streams[videoindex]->codec;
    pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if(pCodec == NULL)
    {
        dbmsg("Codec not found");
        return -1;
    }
    if(avcodec_open2(pCodecCtx, pCodec, NULL) < 0)   //找到解码器之后打开解码器
        return -1;

    pFrame = av_frame_alloc();         //以前的avcodec_alloc_frame函数现在不用了
    pFrameYUV = av_frame_alloc();

    //显示的准备:SDL初始化,设置显示模式,创建画布
    SDL_Init(SDL_INIT_EVERYTHING);
    psscreen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, SDL_SWSURFACE);
    SDL_WM_SetCaption( "FFMPEG Window", NULL);
    //注意这儿的参数SDL_YU12_OVERLAY与SDL_YUY2_OVERLAY一定要与下面sws_scale中的参数配套
    //overlay = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height, SDL_YV12_OVERLAY, psscreen);
    overlay = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height, SDL_YUY2_OVERLAY, psscreen);

    //与SDL的退出相关
    affmutex = SDL_CreateMutex();
    sdl_thread = SDL_CreateThread(eventThread, NULL);    //创建SDL线程监测退出信号

    rect.x = 0;
    rect.y = 0;
    rect.w = pCodecCtx->width;
    rect.h = pCodecCtx->height;

    packet = (AVPacket*)av_malloc(sizeof(AVPacket));
    //注意这儿的参数PIX_FMT_YUV420P或PIX_FMT_YUYU422一定要与上面SDL_CreateYUVOVerlay中的参数配套
    //img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
    img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUYV422, SWS_BICUBIC, NULL, NULL, NULL);
    if(img_convert_ctx == NULL)
    {
        dbmsg("img_convert error");
        return -1;
    }
    //f.循环读取视频文件所有的帧,包括音频帧与视频帧:读取帧到packet
    while( (av_read_frame(pFormatCtx, packet)>=0) && (signal_quit))
    {
        //g.判断是视频帧,则对视频帧解码
        if(packet->stream_index == videoindex)
        {    //解码packet中的视频帧到pFrame中
            if((ret=avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, packet)) < 0)
            {
                dbmsg("decocode video error");
                return -1;
            }
            if(frameFinished)
            {
                SDL_LockYUVOverlay(overlay);
                pFrameYUV->data[0] = overlay->pixels[0];      //Y
                pFrameYUV->data[1] = overlay->pixels[2];      //U   //对overlay中的数据组织不清楚,为什么这儿要把uv交换呢?有知道的告诉我一下,谢谢
                pFrameYUV->data[2] = overlay->pixels[1];      //V
                pFrameYUV->linesize[0] = overlay->pitches[0];
                pFrameYUV->linesize[1] = overlay->pitches[2];
                pFrameYUV->linesize[2] = overlay->pitches[1];
                sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0,
                        pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);    //将解码后pFrame中的数据转为sws_getContext中设定的格式,这样就可以通过sdl进行显示了
                SDL_UnlockYUVOverlay(overlay);
                SDL_DisplayYUVOverlay(overlay, &rect);
                SDL_Delay(40);
            }
        }
    }
    SDL_WaitThread(sdl_thread, &ret);
    SDL_DestroyMutex(affmutex);
    return 0;
}

说明1: SDL_CreateYUVOverlay与sws_getContext中的参数是相对应的
    SDL_CreateYUVOverlay   SDL_YV12_OVERLAY
                                       SDL_YUY2_OVERLAY     
    sws_getContext              PIX_FMT_YUV420P
                                       PIX_FMT_YUYV422    
     SDL_YV12_OVERLAY + PIX_FMT_YUYV422: 则显示不正常 
    SDL_YUY2_OVERLAY + PIX_FMT_YUV420P: 则sws_scale会报错bad dst image pointers
说明2:sws_scale之后就可以把yuv420p数据写到文件中
FILE *fp_yuv;
fp_yuv=fopen("output.yuv","wb+");

int y_size=pCodecCtx->width*pCodecCtx->height;    
fwrite(pFrameYUV->data[0],1,y_size,fp_yuv);    //Y   
fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv);  //U  
fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv);  //V

1.2 Makefile

cong@msi:/work/ffmpeg/test/1view$ cat Makefile
EXE=view
CC=gcc
FFMPEG=/work/ffmpeg/out
CFLAGS=-g -O0 -I$(FFMPEG)/include
LDFLAGS = -L$(FFMPEG)/lib/ -lswscale -lswresample -lavformat -lavdevice -lavcodec -lavutil -lavfilter -lm -lSDL
SRC=$(wildcard *.c)
OBJ=$(patsubst %.c,%.o,$(SRC))
DEP=$(patsubst %.c,.%.d,$(SRC))
$(EXE):$(OBJ)
    $(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS)

$(DEP):.%.d:%.c
    @set -e; rm -f $@; \
    $(CC) -MM  $< > $@.$$$$; \
    sed 's,/($*/)/.o[ :]*,/1.o $@ : ,g' < $@.$$$$ > $@; \
    rm -f $@.$$$$

-include $(DEP)
clean:
    @rm $(EXE) $(OBJ) $(DEP) -f
run:
    export LD_LIBRARY_PATH=$(FFMPEG)/lib/ \
    && ./$(EXE) ../resource/bing.rmvb

2.运行

cong@msi:/work/ffmpeg/test/1view$ make run
export LD_LIBRARY_PATH=/work/ffmpeg/out/lib/ \     -->己经在Makefile中写好了视频文件的路径
    && ./view ../resource/bing.rmvb

3. 代码打包
1view.rar (下载后改名为1view.tar.gz)