ffmpeg2.1对HEVC/H.265视频进行解码的例子

新版的ffmpeg 2.1已经加入了对最新视频编解码标准H.265/HEVC的支持，因此可以解码该格式的视频了。这对视频产业来说将起到一种巨大的推动作用。本文所示的demo是一个简单的H.265格式视频的playback程序，是在http://blog.csdn.net/mu399/article/details/5814859这篇文章的基础上针对新版ffmpeg2.1做了部分修改。与参考文章一样，这个demo同样没有加入播放延迟，所以视频的帧率是不正常的，随着学习的深入会逐渐解决这个问题。工程的下载地址为：http://download.csdn.net/detail/shaqoneal/6571657。

这个工程需要用到ffmpeg和SDL的库，如何将这些库加入到工程中，有很多教程可以参考，就不在这里赘述了，上传到资源中的工程已经设置好了。

文件很简单，头文件如下：

//header.h
#pragma once

#ifdef __cplusplus
extern "C" {
#endif

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

#ifdef __cplusplus
}
#endif

源文件：

//main.cpp
#include "header.h"
#include <stdio.h>
#include "SDL/include/SDL.h"
#include <stdlib.h>
#include <string.h>
#include <math.h> 

static int sws_flags = SWS_BICUBIC; 

int main(int argc, char *argv[])
 {
	AVFormatContext *pFormatCtx = NULL;
    int i, videoStream(-1);
    AVCodecContext *pCodecCtx;
    AVCodec *pCodec;
    AVFrame *pFrame;
    AVPacket packet;
    int frameFinished;
    float aspect_ratio;
    AVCodecContext *aCodecCtx;
    SDL_Overlay *bmp;
    SDL_Surface *screen;
    SDL_Rect rect;
    SDL_Event event;
    if(argc < 2)
    {
        fprintf(stderr, "Usage: test /n");
        exit(1);
    }  

    av_register_all();  

    if(avformat_open_input(&pFormatCtx,argv[1],NULL,NULL))
        return -1; // Couldn't open file
    if(av_find_stream_info(pFormatCtx)<0)
        return -1; // Couldn't find stream information
    // Dump information about file onto standard error
//    dump_format(pFormatCtx, 0, argv[1], 0);  

    // Find the first video stream
    for(i=0; i<pFormatCtx->nb_streams; i++)
    {
        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO && videoStream<0)
        {
            videoStream=i;
        }
    }
    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;
    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  

    // Allocate video frame
    pFrame=avcodec_alloc_frame();  

    uint8_t *buffer;
    int numBytes;
    // 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));  

    if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
    {
        fprintf(stderr, "Could not initialize SDL - %s/n", SDL_GetError());
        exit(1);
    }  

#ifndef __DARWIN__
    screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 0, 0);
#else
    screen = SDL_SetVideoMode(pCodecCtx->width, pCodecCtx->height, 24, 0);
#endif
    if(!screen)
    {
        fprintf(stderr, "SDL: could not set video mode - exiting/n");
        exit(1);
    }  

    bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height,
        SDL_YV12_OVERLAY, screen);  

    static struct SwsContext *img_convert_ctx;
    if (img_convert_ctx == NULL)
    {
        img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
                                         pCodecCtx->pix_fmt,
                                         pCodecCtx->width, pCodecCtx->height,
                                         PIX_FMT_YUV420P,
                                         sws_flags, NULL, NULL, NULL);
        if (img_convert_ctx == NULL)
        {
            fprintf(stderr, "Cannot initialize the conversion context/n");
            exit(1);
        }
    }
    i=0;
    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)
            {
                // Convert the image from its native format to RGB
                /*sws_scale(img_convert_ctx, pFrame->data, pFrame->linesize,
                      0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);*/
                // Save the frame to disk
                /*if(++i<=5)
                    SaveFrame(pFrameRGB, pCodecCtx->width, pCodecCtx->height, i);*/
                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];  

                // Convert the image into YUV format that SDL uses
                /*img_convert(&pict, PIX_FMT_YUV420P,
                    (AVPicture *)pFrame, pCodecCtx->pix_fmt,
                    pCodecCtx->width, pCodecCtx->height);*/
                sws_scale(img_convert_ctx, 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);
                //Sleep(60);
            }
        }  

        // 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
    av_close_input_file(pFormatCtx);
    return 0;
};

今后一段时间里讲尽可能详细地解析上面的每一个类、语句的结构和作用，最终的目的是彻底搞通ffmpeg进行视频处理的原理，可以方便地完成基于ffmpeg的各种开发。一起加油吧！