写这边博客，一方面是因为自己在做项目的时候不太做笔记，怕以后自己忘记了。另一方面，是让正在寻求资料的同行少走一点弯路吧。不能说我这个方案怎么的好，至少是有一点参考价值的。这边博客需要一定基础才能看明白的，当然对V4L2,Swscale,x264,live555不太了解的人，我这里会给出我当时看的资料链接，但愿链接一直有效。也感谢了那些写博客的作者。
下面贴出一些资料的链接吧，认真看完肯定收获不少。
一篇关于V4L2(Video For Linux Two）http://www.cnblogs.com/lixiaoming90/archive/2012/08/25/2657019.html写的很不错的文章，认真看完了，我觉得V4L2视屏捕捉肯定不是问题。
Swscale是ffmpeg库的一部分，主要是做图像格式的转换和拉伸，缩放。这边文章介绍了Swscale的使用，http://blog.csdn.net/leixiaohua1020/article/details/14215391 。
x264是做H264编码用的，要注意的是x264的输入图像格式是：I410也就是420P。这样可以用Swscale对原始图像进行转格式。http://www.cnblogs.com/fojian/archive/2012/09/01/2666627.html 。
live555 是一个流媒体框架，主要是做RTSP协议的。写的很不错(大家都这么说的)，但是读live555源代码还是有一定难度的。这里我就不过多的介绍live555的实现机制了。但是资料还是给出了，感谢作者。http://blog.csdn.net/niu_gao/article/category/1066093 。
下面我开始讲解整个服务器的实现过程吧，
/*
* V4L2.cpp
*
* Created on: 2013年12月17日
* Author: ny
*/ #include "V4L2.h" V4L2::V4L2()
{
fd = -;
buffers = NULL;
width = ;
height = ;
CLEAR(fmt); //设置帧格式
fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUYV; //V4L2_PIX_FMT_YUYV;
fmt.fmt.pix.field = V4L2_FIELD_INTERLACED;
} V4L2::~V4L2()
{
close(fd);
} int V4L2::getWidth()
{
return width;
} int V4L2::getHeight()
{
return height;
} bool V4L2::setSize(int width, int height)
{
fmt.fmt.pix.width = width;
fmt.fmt.pix.height = height;
if (ioctl(fd, VIDIOC_S_FMT, &fmt) == -)
{
printf("Can not VIDIOC_S_FMT\n");
return false;
}
getSizeInfo();
return true;
} void V4L2::getSizeInfo()
{
if (ioctl(fd, VIDIOC_G_FMT, &fmt) == -)
{
printf("Can not VIDIOC_G_FMT\n");
return;
}
this->width = fmt.fmt.pix.width;
this->height = fmt.fmt.pix.height;
} bool V4L2::initDev(const char * devName, int width, int height)
{
v4l2_capability cap; fd = open(devName, O_RDWR, ); //打开设备
if (fd == -)
{
printf("Can not open %s\n", devName);
return false;
}
if (ioctl(fd, VIDIOC_QUERYCAP, &cap) == -) //查询设备的功能
{
printf("Can not get Capability\n");
return false;
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))
{
printf("Can not capture video\n");
return false;
}
if (!(cap.capabilities & V4L2_CAP_STREAMING))
{
printf("does not support streaming\n");
}
if (!setSize(width, height))
return false;
printf("fmt.fmt.pix.bytesperline:%d\n", fmt.fmt.pix.bytesperline);
printf("format:%c%c%c%c\n", (fmt.fmt.pix.pixelformat & 0xff),
((fmt.fmt.pix.pixelformat >> ) & 0xff),
((fmt.fmt.pix.pixelformat >> ) & 0xff),
((fmt.fmt.pix.pixelformat >> ) & 0xff)); return initMmap();
}
bool V4L2::initMmap()
{
struct v4l2_requestbuffers req;
unsigned int n_buffers;
CLEAR(req); req.count = ; //先要想内核申请buffer缓冲，一般选择4个缓冲，最多是5个
req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
req.memory = V4L2_MEMORY_MMAP; if (- == ioctl(fd, VIDIOC_REQBUFS, &req)) //向内核里面设置buffer
{ //分配内存
if (EINVAL == errno)
{
printf("%s does not support memory mapping\n", "ss");
exit(EXIT_FAILURE);
} else
printf("VIDIOC_REQBUFS\n");
} buffers = (buffer *) calloc(req.count, sizeof(buffer)); //分配缓存
if (!buffers)
{
printf("Out of memory\n");
exit(EXIT_FAILURE);
} for (n_buffers = ; n_buffers < req.count; n_buffers++) //将buffer添加到QUERTBUF的队列里面去
{
struct v4l2_buffer buf;
CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers; if (- == ioctl(fd, VIDIOC_QUERYBUF, &buf))
printf("VIDIOC_QUERYBUF"); buffers[n_buffers].length = buf.length; //设置映射方式为mmap
printf("buf.length %d\n", buffers[n_buffers].length);
buffers[n_buffers].start = mmap(NULL, buf.length,
PROT_READ | PROT_WRITE,
MAP_SHARED, fd, buf.m.offset); if (MAP_FAILED == buffers[n_buffers].start)
printf("fail mmap\n");
}
return ;
}
bool V4L2::startStream()
{
unsigned int n_buffers;
enum v4l2_buf_type type;
/*将申请到的帧缓冲全部入队列，以便存放采集到的数据*/
for (n_buffers = ; n_buffers < ; n_buffers++)
{
v4l2_buffer buf;
CLEAR(buf); buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
buf.index = n_buffers; if (- == ioctl(fd, VIDIOC_QBUF, &buf)) //放入缓存
{
printf("fail VIDIOC_QBUF");
return false;
}
} type = V4L2_BUF_TYPE_VIDEO_CAPTURE; if (- == ioctl(fd, VIDIOC_STREAMON, &type)) //打开视频流
{
printf("fail VIDIOC_STREAMON\n");
return false;
} else
printf("StreamOn success!\n");
return true;
}
//摄像头数据 主要是YUYV格式数据，所以需要进行对格式进行转化，转化后的数据保存在AVPicture里面，
//格式是由FMT制定的，输出图像尺寸也是widht_des，height_des决定的
bool V4L2::readFrame(AVPicture & pPictureDes, AVPixelFormat FMT, int widht_des,
int height_des)
{
v4l2_buffer buf;
AVPicture pPictureSrc;
SwsContext * pSwsCtx;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.memory = V4L2_MEMORY_MMAP;
if (- == ioctl(fd, VIDIOC_DQBUF, &buf)) //读取
{
printf("fail VIDIOC_DQBUF\n");
return false;
}
pPictureSrc.data[] = (unsigned char *) buffers[buf.index].start;
pPictureSrc.data[] = pPictureSrc.data[] = pPictureSrc.data[] = NULL;
pPictureSrc.linesize[] = fmt.fmt.pix.bytesperline;
int i = ;
for (i = ; i < ; i++)
{
pPictureSrc.linesize[i] = ;
}
pSwsCtx = sws_getContext(width, height, PIX_FMT_YUYV422, widht_des,
height_des, FMT,
SWS_BICUBIC, , , );
int rs = sws_scale(pSwsCtx, pPictureSrc.data, pPictureSrc.linesize, ,
height, pPictureDes.data, pPictureDes.linesize);
if (rs == -)
{
printf("Can open to change to des image");
return false;
}
sws_freeContext(pSwsCtx);
if (- == ioctl(fd, VIDIOC_QBUF, &buf)) //放回缓存
{
printf("fail VIDIOC_QBUF\n");
return false;
}
return true;
} bool V4L2::stopStream()
{
enum v4l2_buf_type type;
type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
if (- == ioctl(fd, VIDIOC_STREAMOFF, &type))
{
perror("Fail to ioctl 'VIDIOC_STREAMOFF'");
//exit(EXIT_FAILURE);
return false;
}
return true;
}
上面的代码 主要是实现了摄像头的数据捕获，值得注意是函数bool V4L2::readFrame(AVPicture & pPictureDes, AVPixelFormat FMT, int widht_des,
int
height_des)；这个是第一个参数 AVPicture是ffmpeg里面的一个结构体 主要是保存图像的。不过这个参数的初始化在
函数外面，这个大家可以看看那篇swscale的文章就知道了，还有一点就是在函数内部分配的栈数据会在函数结束后销毁的。
/*
* H264Encode.cpp
*
* Created on: 2014年1月4日
* Author: ny
*/ #include <H264Encode.h> H264Encode::H264Encode()
{
i_pts = ;
x264EnCoder = NULL;
pPicOut = NULL;
nnal=;
nals=NULL;
} H264Encode::~H264Encode()
{
} void H264Encode::x264_init(AVPicture picture, int width, int height)
{
x264_param_default_preset(¶m, "veryfast", "zerolatency"); param.i_width = width;
param.i_height = height;
param.i_fps_num = ;
param.i_fps_den = ; param.i_keyint_max = ;
param.b_intra_refresh = ; param.b_annexb = ; x264_param_apply_profile(¶m, "baseline");
x264EnCoder = x264_encoder_open(¶m); x264_picture_alloc(&xPic, X264_CSP_I420, width, height); xPic.img.plane[] = picture.data[];
xPic.img.plane[] = picture.data[];
xPic.img.plane[] = picture.data[];
pPicOut = new x264_picture_t;
} void H264Encode::x264_encode()
{
xPic.i_pts = i_pts++;
x264_encoder_encode(x264EnCoder, &nals, &nnal, &xPic, pPicOut);
}
这部分代码 没什么好讲的 就是这个流程，值得注意的是一帧图像编码后可能生成几个nal，nals是一个nal的指针，nnal表示这帧数据有几个nal。而nal里面保存了数据信息。
/*
* H264OnDemandServerMediaSubsession.cpp
*
* Created on: 2014年1月4日
* Author: ny
*/ #include <H264OnDemandServerMediaSubsession.h>
#include <V4L2FramedSource.h>
#include <live/H264VideoStreamFramer.hh>
#include <live/H264VideoRTPSink.hh> H264OnDemandServerMediaSubsession::H264OnDemandServerMediaSubsession(
UsageEnvironment& env, FramedSource * source) :
OnDemandServerMediaSubsession(env, true)
{
mp_source = source;
mp_sdp_line = NULL;
mp_dummy_rtpsink = NULL;
m_done = ;
} H264OnDemandServerMediaSubsession::~H264OnDemandServerMediaSubsession()
{
} void H264OnDemandServerMediaSubsession::chkForAuxSDPLine1()
{
if (mp_dummy_rtpsink->auxSDPLine())
m_done = 0xff;
else
{
int delay = * ; // 100ms
nextTask() = envir().taskScheduler().scheduleDelayedTask(delay, chkForAuxSDPLine, this);
}
} const char * H264OnDemandServerMediaSubsession::getAuxSDPLine(RTPSink *sink,
FramedSource *source)
{
if (mp_sdp_line)
return mp_sdp_line; mp_dummy_rtpsink = sink;
mp_dummy_rtpsink->startPlaying(*source, , );
//mp_dummy_rtpsink->startPlaying(*source, afterPlayingDummy, this);
chkForAuxSDPLine(this);
m_done = ;
envir().taskScheduler().doEventLoop(&m_done);
mp_sdp_line = strdup(mp_dummy_rtpsink->auxSDPLine());
mp_dummy_rtpsink->stopPlaying(); return mp_sdp_line;
} RTPSink * H264OnDemandServerMediaSubsession::createNewRTPSink(Groupsock *rtpsock, unsigned char type, FramedSource *source)
{
return H264VideoRTPSink::createNew(envir(), rtpsock, type);
} FramedSource * H264OnDemandServerMediaSubsession::createNewStreamSource( unsigned sid, unsigned &bitrate)
{
bitrate = ;
return H264VideoStreamFramer::createNew(envir(), mp_source);
}
char const* H264OnDemandServerMediaSubsession::sdpLines()
{
return fSDPLines = (char *)
"m=video 0 RTP/AVP 96\r\n"
"c=IN IP4 0.0.0.0\r\n"
"b=AS:96\r\n"
"a=rtpmap:96 H264/90000\r\n"
"a=fmtp:96 packetization-mode=1;profile-level-id=000000;sprop-parameter-sets=H264\r\n"
"a=control:track1\r\n";
}
H264OnDemandServerMediaSubsession类主要是继承了H264OnDemandServerMediaSubsession类。主要是为了设置SDP 描述。
sdpLines()这个函数 需要根据自己的实际情况进行改写的。关于里面的含义，我这里就不多解释了，熟悉一下RTSP协议就可以完全知道含义了。
/*
* V4L2FramedSource.cpp
*
* Created on: 2014年1月4日
* Author: ny
*/ #include <V4L2FramedSource.h> int V4L2FramedSource::nalIndex = ; V4L2FramedSource::V4L2FramedSource(UsageEnvironment & env) :
FramedSource(env)
{
v4l2 = new V4L2();
pEncode = new H264Encode();
mp_token = NULL;
printf("creater\n");
v4l2->initDev("/dev/video0", , );
avpicture_alloc(&Picture, PIX_FMT_YUV420P, v4l2->getWidth(), v4l2->getHeight());
v4l2->startStream(); pEncode->x264_init(Picture, , );
} V4L2FramedSource::~V4L2FramedSource()
{
} unsigned V4L2FramedSource::maxFrameSize() const
{
return * ;
} void V4L2FramedSource::doGetNextFrame()
{
/*double delay = 1000.0 / 25;
int to_delay = delay * 1000; // us
mp_token = envir().taskScheduler().scheduleDelayedTask(to_delay,
getNextFrame, this);*/
if (V4L2FramedSource::nalIndex == pEncode->nnal)
{
v4l2->readFrame(Picture, PIX_FMT_YUV420P, v4l2->getWidth(), v4l2->getHeight());
pEncode->x264_encode();
V4L2FramedSource::nalIndex = ;
gettimeofday(&fPresentationTime, NULL);
}
memmove(fTo,
pEncode->nals[V4L2FramedSource::nalIndex].p_payload,
pEncode->nals[V4L2FramedSource::nalIndex].i_payload);
fFrameSize = pEncode->nals[V4L2FramedSource::nalIndex].i_payload;
V4L2FramedSource::nalIndex++;
afterGetting(this);
} void V4L2FramedSource::getNextFrame1()
{ } /*
V4L2FramedSource类继承了FramedSource类。V4L2FramedSource是我们自定义的类，主要实现了我们的视频数据如何进入到live555里面去。首先在构造函数里面，我们对v4l2进行了初始化以及x264编码初始化。这个类最重要的就是<SPAN style="BACKGROUND-COLOR: rgb(240,240,240)">doGetNextFrame函数，live555就是通过这个函数将我们的一个nal数据加载到live555里面，然后消息循环发送出去的。我们先是将v4l2捕捉的视频数据进行H264压缩编码，这里面值得注意的是一帧图像可能压缩成几个nal的，所以我这里面在确保一帧数据完全发送完了才向v4l2要数据。然后就是数据的般移了，其中数据存在fTo里面。然后就是消息了。
*/ /*
* Application.cpp
*
* Created on: 2014年1月4日
* Author: ny
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> #include "H264OnDemandServerMediaSubsession.h"
#include "V4L2FramedSource.h" #include <live/liveMedia.hh>
#include <live/BasicUsageEnvironment.hh>
#include <live/UsageEnvironment.hh> UsageEnvironment* env;
static void announceStream(RTSPServer* rtspServer, ServerMediaSession* sms,
char const* streamName, char const* inputFileName = "Live"); // fwd
int main()
{
// 设置使用环境。Begin by setting up our usage environment:
TaskScheduler* scheduler = BasicTaskScheduler::createNew();
env = BasicUsageEnvironment::createNew(*scheduler);
UserAuthenticationDatabase* authDB = NULL; RTSPServer* rtspServer = RTSPServer::createNew(*env, , authDB);
if (rtspServer == NULL)
{
*env << "Failed to create RTSP server: " << env->getResultMsg() << "\n";
exit();
} char const* descriptionString =
"Session streamed by \"testOnDemandRTSPServer\"";
char const* streamName = "live";
ServerMediaSession* sms = ServerMediaSession::createNew(*env, streamName,
streamName, descriptionString);
sms->addSubsession(new H264OnDemandServerMediaSubsession(*env,
new V4L2FramedSource(*env)));
rtspServer->addServerMediaSession(sms);
announceStream(rtspServer, sms, streamName);
env->taskScheduler().doEventLoop(); // does not return return ;
}
static void announceStream(RTSPServer* rtspServer, ServerMediaSession* sms,
char const* streamName, char const* inputFileName)
{
char* url = rtspServer->rtspURL(sms);
UsageEnvironment& env = rtspServer->envir();
env << "\n\"" << streamName << "\" stream, from the file \""
<< inputFileName << "\"\n";
env << "Play this stream using the URL \"" << url << "\"\n";
delete[] url;
}
/*
这是我们程序的主程序，主要是参考了live555的testOnDemandRTSPServer.cpp。主要是区别是我们自己指定了rtsp链接了，以及我们自己实现的framesource。这样本地的视频采集发送服务器就完成了，可以用开源的VLC播放进行播放了，live555支持1对多的，已经测试过可以在ipad，iphone，android同步播放，延迟在1s以内。不过要VLC设置缓存时间在200ms就可以了。
*/