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=0,
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：
1 struct hvplayer
2 {
3 playend_cb end;
4 int32_t hwnd;
5 int32_t flage;
6 char *url;
7 enum player_state ste;
8 HANDLE thread;
9 clock_t pretm;
10 int play;
11 };
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.
1 static int play_loop(void* p)
2 {
3 hvplayer *h=(hvplayer*)p;
4 while(h->flage)
5 {
6 h->ste=PLAYER_CONNECTING;
7 h->pretm=clock();
8 _do(h);
9 int s=TIMEOUT_S-(clock()-h->pretm)/CLOCKS_PER_SEC;
10 if(s>0) Sleep(s*1000);
11 }
12 if(h->end) h->end(h);
13 free(h->url);
14 free(h);
15 return 1;
16 }
1 static void _do(hvplayer*h)
2 {
3 AVCodec *codec=NULL;
4 AVCodecContext *cc=NULL;
5 AVPacket pk={0};
6 AVFormatContext *afc=NULL;
7 int vindex=-1;
8 afc=avformat_alloc_context();
9 if(afc==0){
10 goto err;
11 }
12 afc->interrupt_callback.callback=timeoutcheck;
13 afc->interrupt_callback.opaque=h;
14 AVDictionary *dir=NULL;
15 char *k1="stimeout";
16 char *v1="10";
17 char *k2="rtsp_transport";
18 char *v2="tcp";
19 char *k4="max_delay";
20 char *v4="50000";
21 int r=av_dict_set(&dir,k1,v1,0);
22 r=av_dict_set(&dir,k2,v2,0);
23 av_dict_set(&dir,k4,v4,0);
24 if(avformat_open_input(&afc,h->url,NULL,&dir)) {
25 goto err;
26 }
27 if(avformat_find_stream_info(afc,NULL)<0) {
28 goto err;
29 }
30 for(int i=0;i<(int)afc->nb_streams;i++)
31 {
32 if(afc->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
33 {
34 vindex=i;
35 break;
36 }
37 }
38 if(vindex==-1){
39 goto err;
40 }
41 cc=afc->streams[vindex]->codec;
42 codec=avcodec_find_decoder(cc->codec_id);
43
44 if(codec==0) goto end;
45 if(avcodec_open2(cc,codec,NULL)<0) {
46 goto err;
47 }
48 int dr;
49 hvframe frame;
50 render *render=render_create(RENDER_TYPE_D3D,h->hwnd,cc->coded_width,cc->coded_height);
51 if(render==NULL)
52 {
53 render=render_create(RENDER_TYPE_GDI,h->hwnd,cc->coded_width,cc->coded_height);
54 if(render==NULL){
55 goto end;
56 }
57 }
58 AVFrame *yuv_buf=av_frame_alloc();
59 if(yuv_buf==0) {
60 goto end;
61 }
62 h->ste=PLAYER_PLAYING;
63 DWORD a,b;
64 while (h->flage&&av_read_frame(afc,&pk)>=0)
65 {
66
67 if(pk.stream_index==vindex)
68 {
69 avcodec_decode_video2(cc,yuv_buf,&dr,&pk);
70 if(dr>0)
71 {
72 frame.h=cc->coded_height;
73 frame.y=yuv_buf->data[0];
74 frame.u=yuv_buf->data[1];
75 frame.v=yuv_buf->data[2];
76 frame.ypitch=yuv_buf->linesize[0];
77 frame.uvpitch=yuv_buf->linesize[1];
78 render->draw(render,&frame);
79 }
80 }
81 av_free_packet(&pk);
82 }
83 end:
84 if(yuv_buf) av_frame_free(&yuv_buf);
85 if(render) render->destory(&render);
86 err:
87 if(cc) avcodec_close(cc);
88 if(afc){
89 avformat_close_input(&afc);
90 avformat_free_context(afc);
91 }
92 }
- avformat_alloc_context（）分配AVFormatContext对象。
- 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):
1 #define TIMEOUT_S 6
2
3 int timeoutcheck(void *p)
4 {
5 hvplayer *h=(hvplayer*)p;
6 if(h->flage==0) return 1;
7 if(h->ste==PLAYER_CONNECTING)
8 {
9 clock_t ctm=clock();
10 int s=(ctm-h->pretm)/CLOCKS_PER_SEC;
11 if(s>=TIMEOUT_S)
12 return 1;
13 }
14 return 0;
15 }
3、avformat_find_stream_info()解析流的格式信息，再用以下代码获取AVCodecContext:
1 for(int i=0;i<(int)afc->nb_streams;i++)
2 {
3 if(afc->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO)
4 {
5 vindex=i;
6 break;
7 }
8 }
9 if(vindex==-1){
10 goto err;
11 }
12 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：
1 struct render{
2 int hwnd;
3 void (*draw)(struct render *self,hvframe *frame);
4 void (*destory)(struct render **self);
5 };
6 typedef struct render render;
d3d实现如下：
1 #include <stdlib.h>
2 #include "hvtype.h"
3 #include "irender.h"
4 #include "winapi.h"
5 struct render_d3d
6 {
7 render base;
8 IDirect3D9 *d3d;
9 IDirect3DDevice9 *d3d_dev;
10 IDirect3DSurface9 *surface;
11 RECT rec;
12 };
13
14 void d3d_draw(render *h,hvframe *frame);
15 void render_free(render **h);
16
17 render *d3d_new(int hwnd,int pic_w,int pic_h)
18 {
19 struct render_d3d *result=(struct render_d3d *)malloc(sizeof(*result));
20 result->base.hwnd=hwnd;
21 result->d3d=Direct3DCreate9(D3D_SDK_VERSION);
22 if(result->d3d==NULL) return NULL;
23 D3DPRESENT_PARAMETERS d3dpp;
24 memset(&d3dpp,0,sizeof(d3dpp));
25 d3dpp.Windowed=TRUE;
26 d3dpp.SwapEffect=D3DSWAPEFFECT_DISCARD;
27 d3dpp.BackBufferFormat=D3DFMT_UNKNOWN;
28 GetClientRect((HWND)result->base.hwnd,&result->rec);
29 HRESULT re=IDirect3D9_CreateDevice(result->d3d,D3DADAPTER_DEFAULT,D3DDEVTYPE_HAL,(HWND)result->base.hwnd,
30 D3DCREATE_SOFTWARE_VERTEXPROCESSING,&d3dpp,&result->d3d_dev);
31 if(FAILED(re)) return NULL;
32 re=IDirect3DDevice9_CreateOffscreenPlainSurface(result->d3d_dev,pic_w,pic_h,
33 (D3DFORMAT)MAKEFOURCC('Y','V','1','2'),
34 D3DPOOL_DEFAULT,&result->surface,NULL);
35 if(FAILED(re)) return NULL;
36 result->base.draw=d3d_draw;
37 result->base.destory=render_free;
38 return (render *)result;
39 }
40
41 void d3d_draw(render *h,hvframe *frame)
42 {
43 struct render_d3d *self=(struct render_d3d*)h;
44 D3DLOCKED_RECT texture;
45 HRESULT re=IDirect3DSurface9_LockRect(self->surface,&texture,NULL,D3DLOCK_DONOTWAIT);
46 if(FAILED(re)) return;
47 int uvstep=texture.Pitch/2;
48 char *dest=(char*)texture.pBits;
49 char *vdest=(char*)texture.pBits+frame->h*texture.Pitch;
50 char *udest=(char*)vdest+frame->h/2*uvstep;
51 int uvn=0;
52 for(int i=0;i<frame->h;i++)
53 {
54 memcpy(dest,frame->y,frame->ypitch);
55 frame->y+=frame->ypitch;
56 dest+=texture.Pitch;
57 }
58 for(int i=0;i<frame->h/2;i++)
59 {
60 memcpy(vdest,frame->v,frame->uvpitch);
61 memcpy(udest,frame->u,frame->uvpitch);
62 vdest+=uvstep;
63 udest+=uvstep;
64 frame->v+=frame->uvpitch;
65 frame->u+=frame->uvpitch;
66 }
67 IDirect3DSurface9_UnlockRect(self->surface);
68 IDirect3DDevice9_BeginScene(self->d3d_dev);
69 IDirect3DSurface9 *back_surface;
70 IDirect3DDevice9_GetBackBuffer(self->d3d_dev,0,0,D3DBACKBUFFER_TYPE_MONO,&back_surface);
71 IDirect3DDevice9_StretchRect(self->d3d_dev,self->surface,NULL,back_surface,&self->rec,D3DTEXF_LINEAR);
72 IDirect3DDevice9_EndScene(self->d3d_dev);
73 IDirect3DDevice9_Present(self->d3d_dev,NULL,NULL,NULL,NULL);
74 }
75 void render_free(render **h)
76 {
77 if((*h)==0)return;
78 struct render_d3d *self=(struct render_d3d*)(*h);
79 IDirect3DDevice9_Clear(self->d3d_dev,0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0,0,0), 1.0f, 0 );
80 IDirect3DDevice9_Present(self->d3d_dev,NULL,NULL,NULL,NULL);
81 IDirect3DSurface9_Release(self->surface);
82 IDirect3DDevice9_Release(self->d3d_dev);
83 IDirect3D9_Release(self->d3d);
84 free(*h);
85 *h=0;
86 }
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：
1 #include <stdlib.h>
2 #include <windows.h>
3 #include "hvpfconvert.h"
4 #include "irender.h"
5 #include "winapi.h"
6
7 struct render_gdi
8 {
9 render base;
10 BITMAPINFO bmp;
11 HDC dc;
12 hvpfconvert *convert;
13 uint8_t *buf;
14 RECT rec;
15 };
16
17
18 void gdi_free(render **h)
19 {
20 if((*h)==0)return;
21 struct render_gdi *self=(struct render_gdi*)(*h);
22 FillRect(self->dc,&self->rec,(HBRUSH)(pGetStockObject(BLACK_BRUSH)));
23 ReleaseDC((HWND)self->base.hwnd,self->dc);
24 hvpfconvert_free(&self->convert);
25 free(*h);
26 *h=0;
27 }
28
29 void gdi_draw(render *h,hvframe *frame)
30 {
31 struct render_gdi *self=(struct render_gdi*)h;
32 hvpfconvert_convert2(self->convert, frame, self->buf);
33 pSetStretchBltMode(self->dc, STRETCH_HALFTONE);
34 pStretchDIBits(self->dc, 0, 0, self->rec.right, self->rec.bottom, 0, 0,
35 self->bmp.bmiHeader.biWidth, frame->h, self->buf, &self->bmp, DIB_RGB_COLORS, SRCCOPY);
36 }
37
38 render *gdi_new(int32_t hwnd,int pic_w,int pic_h)
39 {
40 struct render_gdi *re = (struct render_gdi *)calloc(1,sizeof(*re));
41 re->convert = hvpfconvert_new(pic_w, pic_h, pic_w, pic_h, PF_YUV420P, PF_BGR24);
42 re->dc = GetDC((HWND)hwnd);
43 re->base.hwnd = hwnd;
44 GetClientRect((HWND)re->base.hwnd, &re->rec);
45 re->buf = (uint8_t*)malloc(hvpfconvert_get_size(pic_w, pic_h, PF_RGB24));
46 re->bmp.bmiHeader.biBitCount = 24;
47 re->bmp.bmiHeader.biClrImportant = BI_RGB;
48 re->bmp.bmiHeader.biClrUsed = 0;
49 re->bmp.bmiHeader.biCompression = 0;
50 re->bmp.bmiHeader.biHeight = -pic_h;
51 re->bmp.bmiHeader.biWidth = pic_w;
52 re->bmp.bmiHeader.biPlanes = 1;
53 re->bmp.bmiHeader.biSize = sizeof(re->bmp.bmiHeader);
54 re->bmp.bmiHeader.biSizeImage = pic_w*pic_h * 3;
55 re->bmp.bmiHeader.biXPelsPerMeter = 0;
56 re->bmp.bmiHeader.biYPelsPerMeter = 0;
57 re->base.destory=gdi_free;
58 re->base.draw=gdi_draw;
59 return (render *)re;
60 }
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：
1 int hvdevicevideo_init(void){
2 if(hv_winapi_init()) return -1;
3 avcodec_register_all();
4 av_register_all();
5 avformat_network_init();
6 sdk_init=1;
7 CoInitializeEx(NULL,COINIT_MULTITHREADED);
8 return 0;
9 }
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.