利用ffmpeg进行视频软解播放

前段时间，公司的一个项目需要一个rtsp的播放库，原本打算直接用vlc播放的，但我觉得vlc太庞大了，很多功能没必要，还不如用ffmpeg+d3d简单的实现一个库，因此就有了今天讲的这个东西。一个解码库，分为三个部分：网络，解码，显示。网络和解码在ffmpeg里带了，直接用就好，显示，用d3d直接显示yuv是最佳方案了。整个库采用多线程模型，播放一路就创建一个播放线程。库的接口如下：

struct hvplayer;
typedef struct hvplayer hvplayer;
/**
 *播放退出回调
 *@param h 播放器指针
 *@param state 退出状态
 */
typedef void (*playend_cb)(hvplayer *h);

enum player_state
{
    PLAYER_CONNECTING=,
    PLAYER_PLAYING,
    PLAYER_OFF
};

/**
 *初始化一个播放器
 *@param hwnd 一个表示画面显示区域的id,windows上为窗口句柄
 *@param url rtsp地址
 *@return NULL失败,>0为一个播放器指针
 */
HVEXP hvplayer *hvplayer_new(int32_t hwnd, const char *url);

/**
 *播放一个rtsp视频,该方法是一个非阻塞函数,内部会创建一个线程去执行播放
 *任务，自动无限重连，直到调用hvplayer_close
 *
 *@param h 一个指向播放器的指针
 *@return 成功为0,失败-1
 */
 HVEXP int hvplayer_play(hvplayer *h);

/**
 *获取播放器的状态,成功会设置state
 *
 *@param h 一个指向播放器的指针
 *@return player_state枚举的值
 */
 HVEXP int hvplayer_getstate(hvplayer *h);

/**
 *停止播放,并结束播放线程,该方法会阻塞至播放线程结束,同时释放hvplayer句柄
 *
 *@param h 一个指向播放器的指针
 */
 HVEXP void hvplayer_close(hvplayer *h);

/**
 *注册播放结束回调,hvplayer_close后回调会被调用
 *
 *@param h 一个指向播放器的指针
 *@param cb 具体见回调定义
 *@waring 多次注册会覆盖
 *@waring 不要阻塞该调用线程
 */
 HVEXP void hvplayer_set_endcb(hvplayer *h, playend_cb cb);
 /************************************************************************/
 /*SDK初始化,必须在使用SDK之前初始化
  *@return 0成功
 /************************************************************************/
 HVEXP int hvdevicevideo_init(void);

使用起来很简单，一个hvplayer对象对应一路视频，先hvplayer_new(),在hvplayer_play(),最后hvplayer_close()就好了。库使用前要调用hvdevicevideo_init进行初始化.
hvplayer的定义如下：

 struct hvplayer
 {
     playend_cb end;
     int32_t hwnd;
     int32_t flage;
     char *url;
     enum player_state ste;
     HANDLE thread;
     clock_t pretm;
     int play;
 };

flage是控制重连循环的，play是控制帧数据读取循环的,pretm是控制rtsp服务器连接超时的.

play_loop是播放线程的函数，外层是重连循环,_do是实际播放循环.

 static int play_loop(void* p)
 {
     hvplayer *h=(hvplayer*)p;
     while(h->flage)
     {
         h->ste=PLAYER_CONNECTING;
         h->pretm=clock();
         _do(h);
         int s=TIMEOUT_S-(clock()-h->pretm)/CLOCKS_PER_SEC;
         if(s>) Sleep(s*);
     }
     if(h->end) h->end(h);
     free(h->url);
     free(h);
     return ;
 }

 static void _do(hvplayer*h)
 {
     AVCodec *codec=NULL;
     AVCodecContext *cc=NULL;
     AVPacket pk={};
     AVFormatContext *afc=NULL;
     int vindex=-;
     afc=avformat_alloc_context();
     if(afc==){
         goto err;
     }
     afc->interrupt_callback.callback=timeoutcheck;
     afc->interrupt_callback.opaque=h;
     AVDictionary *dir=NULL;
     char *k1="stimeout";
     char *v1="";
     char *k2="rtsp_transport";
     char *v2="tcp";
     char *k4="max_delay";
     char *v4="";
     int r=av_dict_set(&dir,k1,v1,);
     r=av_dict_set(&dir,k2,v2,);
     av_dict_set(&dir,k4,v4,);
     if(avformat_open_input(&afc,h->url,NULL,&dir)) {
         goto err;
     }
     if(avformat_find_stream_info(afc,NULL)<) {
         goto err;
     }
     for(int i=;i<(int)afc->nb_streams;i++)
     {
         if(afc->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
         {
             vindex=i;
             break;
         }
     }
     if(vindex==-){
         goto err;
     }
     cc=afc->streams[vindex]->codec;
     codec=avcodec_find_decoder(cc->codec_id);

     if(codec==) goto end;
     if(avcodec_open2(cc,codec,NULL)<) {
         goto err;
     }
     int dr;
     hvframe frame;
     render *render=render_create(RENDER_TYPE_D3D,h->hwnd,cc->coded_width,cc->coded_height);
     if(render==NULL)
     {
         render=render_create(RENDER_TYPE_GDI,h->hwnd,cc->coded_width,cc->coded_height);
         if(render==NULL){
             goto end;
         }
     }
     AVFrame *yuv_buf=av_frame_alloc();
     if(yuv_buf==) {
         goto end;
     }
     h->ste=PLAYER_PLAYING;
     DWORD a,b;
     while (h->flage&&av_read_frame(afc,&pk)>=)
     {

         if(pk.stream_index==vindex)
         {
                 avcodec_decode_video2(cc,yuv_buf,&dr,&pk);
                 if(dr>)
                 {
                     frame.h=cc->coded_height;
                     frame.y=yuv_buf->data[];
                     frame.u=yuv_buf->data[];
                     frame.v=yuv_buf->data[];
                     frame.ypitch=yuv_buf->linesize[];
                     frame.uvpitch=yuv_buf->linesize[];
                     render->draw(render,&frame);
                 }
         }
         av_free_packet(&pk);
     }
 end:
     if(yuv_buf) av_frame_free(&yuv_buf);
     if(render) render->destory(&render);
 err:
     if(cc) avcodec_close(cc);
     if(afc){
         avformat_close_input(&afc);
         avformat_free_context(afc);
     }
 }

1. avformat_alloc_context（）分配AVFormatContext对象。
2. avformat_open_input（）打开一个流媒体源，可以是文件，rtsp,这是一个阻塞函数，知道解析成功或失败才返回.那如何设置超时时间呢？这个对象提供了两个中断回调，解析时ffmpeg会以一定频率调用这个回调，这个回调的返回值影响avformat_open_input（）是否立马返回.这个回调函数指针就是AVFormatContext->interrupt_callback.callback,同时可以用->interrupt_callback.opaque绑定一个用户数据.回调函数返回1时，avformat_open_input（）会失败返回,返回0则正常运行.

我是这样处理的(为了6秒超时判定):

 #define  TIMEOUT_S 6

 int timeoutcheck(void *p)
 {
     hvplayer *h=(hvplayer*)p;
     if(h->flage==) return ;
     if(h->ste==PLAYER_CONNECTING)
     {
         clock_t ctm=clock();
         int s=(ctm-h->pretm)/CLOCKS_PER_SEC;
         if(s>=TIMEOUT_S)
             return ;
     }
     return ;
 }

　　3、avformat_find_stream_info()解析流的格式信息，再用以下代码获取AVCodecContext:

 for(int i=;i<(int)afc->nb_streams;i++)
     {
         if(afc->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
         {
             vindex=i;
             break;
         }
     }
     if(vindex==-){
         goto err;
     }
     cc=afc->streams[vindex]->codec;

　　4、avcodec_find_decoder(),利用AVCodecContext->codec_id创建AVCodec,再用avcodec_open2()打开解码器.

　　5、循环调用av_read_frame()获取一帧编码数据，再调用avcodec_decode_video2(AVCodec*,AVFrame*,int*,AVPacket*)解码为yuv,第三个参数标示是否解码成功(>0成功),最后调用显示模块显示即可.

显示上，我将其封装为render对象，分别实现了d3d,gdi.render的结构如下：

 struct render{
     int hwnd;
     void (*draw)(struct render *self,hvframe *frame);
     void (*destory)(struct render **self);
 };
 typedef struct render render;

d3d实现如下：

 #include <stdlib.h>
 #include "hvtype.h"
 #include "irender.h"
 #include "winapi.h"
 struct render_d3d
 {
     render base;
     IDirect3D9 *d3d;
     IDirect3DDevice9 *d3d_dev;
     IDirect3DSurface9 *surface;
     RECT rec;
 };

 void d3d_draw(render *h,hvframe *frame);
 void render_free(render **h);

 render *d3d_new(int hwnd,int pic_w,int pic_h)
 {
     struct render_d3d *result=(struct render_d3d *)malloc(sizeof(*result));
     result->base.hwnd=hwnd;
     result->d3d=Direct3DCreate9(D3D_SDK_VERSION);
     if(result->d3d==NULL) return NULL;
     D3DPRESENT_PARAMETERS d3dpp;
     memset(&d3dpp,,sizeof(d3dpp));
     d3dpp.Windowed=TRUE;
     d3dpp.SwapEffect=D3DSWAPEFFECT_DISCARD;
     d3dpp.BackBufferFormat=D3DFMT_UNKNOWN;
     GetClientRect((HWND)result->base.hwnd,&result->rec);
     HRESULT re=IDirect3D9_CreateDevice(result->d3d,D3DADAPTER_DEFAULT,D3DDEVTYPE_HAL,(HWND)result->base.hwnd,
         D3DCREATE_SOFTWARE_VERTEXPROCESSING,&d3dpp,&result->d3d_dev);
     if(FAILED(re)) return NULL;
     re=IDirect3DDevice9_CreateOffscreenPlainSurface(result->d3d_dev,pic_w,pic_h,
         (D3DFORMAT)MAKEFOURCC('Y','V','',''),
         D3DPOOL_DEFAULT,&result->surface,NULL);
     if(FAILED(re)) return NULL;
     result->base.draw=d3d_draw;
     result->base.destory=render_free;
     return (render *)result;
 }

 void d3d_draw(render *h,hvframe *frame)
 {
     struct render_d3d *self=(struct render_d3d*)h;
     D3DLOCKED_RECT texture;
     HRESULT re=IDirect3DSurface9_LockRect(self->surface,&texture,NULL,D3DLOCK_DONOTWAIT);
     if(FAILED(re)) return;
     int uvstep=texture.Pitch/;
     char *dest=(char*)texture.pBits;
     char *vdest=(char*)texture.pBits+frame->h*texture.Pitch;
     char *udest=(char*)vdest+frame->h/*uvstep;
     int uvn=;
     for(int i=;i<frame->h;i++)
     {
         memcpy(dest,frame->y,frame->ypitch);
         frame->y+=frame->ypitch;
         dest+=texture.Pitch;
     }
     for(int i=;i<frame->h/;i++)
     {
         memcpy(vdest,frame->v,frame->uvpitch);
         memcpy(udest,frame->u,frame->uvpitch);
         vdest+=uvstep;
         udest+=uvstep;
         frame->v+=frame->uvpitch;
         frame->u+=frame->uvpitch;
     }
     IDirect3DSurface9_UnlockRect(self->surface);
     IDirect3DDevice9_BeginScene(self->d3d_dev);
     IDirect3DSurface9 *back_surface;
     IDirect3DDevice9_GetBackBuffer(self->d3d_dev,,,D3DBACKBUFFER_TYPE_MONO,&back_surface);
     IDirect3DDevice9_StretchRect(self->d3d_dev,self->surface,NULL,back_surface,&self->rec,D3DTEXF_LINEAR);
     IDirect3DDevice9_EndScene(self->d3d_dev);
     IDirect3DDevice9_Present(self->d3d_dev,NULL,NULL,NULL,NULL);
 }
 void render_free(render **h)
 {
     if((*h)==)return;
     struct render_d3d *self=(struct render_d3d*)(*h);
     IDirect3DDevice9_Clear(self->d3d_dev,, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(,,), 1.0f,  );
     IDirect3DDevice9_Present(self->d3d_dev,NULL,NULL,NULL,NULL);
     IDirect3DSurface9_Release(self->surface);
     IDirect3DDevice9_Release(self->d3d_dev);
     IDirect3D9_Release(self->d3d);
     free(*h);
     *h=;
 }

都是标准的固定管线步骤，就不赘述了，唯一要注意的就是yuv数据填充到surface中时要注意行对齐.

gdi实现如下：

 #include <stdlib.h>
 #include <windows.h>
 #include "hvpfconvert.h"
 #include "irender.h"
 #include "winapi.h"

 struct render_gdi
 {
     render base;
     BITMAPINFO  bmp;
     HDC dc;
     hvpfconvert *convert;
     uint8_t *buf;
     RECT rec;
 };

 void gdi_free(render **h)
 {
     if((*h)==)return;
     struct render_gdi *self=(struct render_gdi*)(*h);
     FillRect(self->dc,&self->rec,(HBRUSH)(pGetStockObject(BLACK_BRUSH)));
     ReleaseDC((HWND)self->base.hwnd,self->dc);
     hvpfconvert_free(&self->convert);
     free(*h);
     *h=;
 }

 void gdi_draw(render *h,hvframe *frame)
 {
     struct render_gdi *self=(struct render_gdi*)h;
     hvpfconvert_convert2(self->convert, frame, self->buf);
     pSetStretchBltMode(self->dc, STRETCH_HALFTONE);
     pStretchDIBits(self->dc, , , self->rec.right, self->rec.bottom, , ,
         self->bmp.bmiHeader.biWidth, frame->h, self->buf, &self->bmp, DIB_RGB_COLORS, SRCCOPY);
 }

 render *gdi_new(int32_t hwnd,int pic_w,int pic_h)
 {
     struct render_gdi *re = (struct render_gdi *)calloc(,sizeof(*re));
     re->convert = hvpfconvert_new(pic_w, pic_h, pic_w, pic_h, PF_YUV420P, PF_BGR24);
     re->dc = GetDC((HWND)hwnd);
     re->base.hwnd = hwnd;
     GetClientRect((HWND)re->base.hwnd, &re->rec);
     re->buf = (uint8_t*)malloc(hvpfconvert_get_size(pic_w, pic_h, PF_RGB24));
     re->bmp.bmiHeader.biBitCount = ;
     re->bmp.bmiHeader.biClrImportant = BI_RGB;
     re->bmp.bmiHeader.biClrUsed = ;
     re->bmp.bmiHeader.biCompression = ;
     re->bmp.bmiHeader.biHeight = -pic_h;
     re->bmp.bmiHeader.biWidth = pic_w;
     re->bmp.bmiHeader.biPlanes = ;
     re->bmp.bmiHeader.biSize = sizeof(re->bmp.bmiHeader);
     re->bmp.bmiHeader.biSizeImage = pic_w*pic_h * ;
     re->bmp.bmiHeader.biXPelsPerMeter = ;
     re->bmp.bmiHeader.biYPelsPerMeter = ;
     re->base.destory=gdi_free;
     re->base.draw=gdi_draw;
     return (render *)re;
 }

gdi是利用StretchDIBits函数显示位图，因此要将yuv转换为rgb数据，图像格式转换，ffmpeg也自带了高效的转换函数:sws_scale().

最后是sdk的初始化，hvdevicevideo_init()我调用了ffmpeg库和d3d所需的初始化函数：

 int hvdevicevideo_init(void){
     if(hv_winapi_init()) return -;
     avcodec_register_all();
     av_register_all();
     avformat_network_init();
     sdk_init=;
     CoInitializeEx(NULL,COINIT_MULTITHREADED);
     return ;
 }

最后整个库，性能还不错，不必vlc差。在支持d3d的i5机器上解码一路1080p视频占3%-5%左右的cpu.不支持的将启用gdi显示，每路占13%的cpu.可优化点是rtsp，ffmpeg的rtsp效率
一般般，基本有400毫秒左右的延迟，而liv555可以做到200的延迟，不过我的需求400延迟可以接受，因此就没去折腾了。后来公司有一嵌入式的项目，我又做了一版linux的实现，用了英特尔的vaapi驱动进行硬解码(因为项目运行的机器是一款atom的cpu,主频只有1.2g,软解一路要占40%多的cpu),后续再写基于ffmpeg的vaapi硬解码播放吧.