motion源代码分析

本文主要是介绍motion源代码分析，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

转自：http://blog.csdn.net/sakaue/article/details/22816475

楔子

前几天研究了如何将ffmpeg编入motion，并实现录像功能。现在研究下motion的工作流程。

几个主要模块

motion.c	主程序，视频采集编码主循环
ffmpeg.c	一个代理模块，封装了ffmpeg的方法，根据v4l获取的数据编码录像
video.2.c	提供video4linux功能
video_common.c	封装video.2.c中功能，为motion.c提供支持
vebhttpd.c	向客户端提供控制功能
webcam.c	向客户端提供实时图像服务（浏览器刷图片）

正文

照例从main函数进入。在这里，main起了两个线程，一个是集视频采集录像放送于一体的motion_loop：

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/* Start the motion threads. First 'cnt_list' item is global if 'thread'
* option is used, so start at 1 then and 0 otherwise.
*/
for (i = cnt_list[1] != NULL ? 1 : 0; cnt_list[i]; i++) {
/* If i is 0 it means no thread files and we then set the thread number to 1 */
cnt_list[i]->threadnr = i ? i : 1;
if (strcmp(cnt_list[i]->conf_filename,"") )
motion_log(LOG_INFO, 0, "Thread %d is from %s", cnt_list[i]->threadnr, cnt_list[i]->conf_filename );
if (cnt_list[0]->conf.setup_mode) {
motion_log(-1, 0, "Thread %d is device: %s input %d", cnt_list[i]->threadnr,
cnt_list[i]->conf.netcam_url ? cnt_list[i]->conf.netcam_url : cnt_list[i]->conf.video_device,
cnt_list[i]->conf.netcam_url ? -1 : cnt_list[i]->conf.input
);
}
if (cnt_list[0]->conf.setup_mode)
motion_log(LOG_ERR, 0, "Webcam port %d", cnt_list[i]->conf.webcam_port);
start_motion_thread(cnt_list[i], &thread_attr); //在这里启动线程函数motion_loop
}

一个是用于web控制的motion_web_control：

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/* Create a thread for the control interface if requested. Create it
* detached and with 'motion_web_control' as the thread function.
*/
if (cnt_list[0]->conf.control_port)
pthread_create(&thread_id, &thread_attr, &motion_web_control, cnt_list); //启动线程函数motion_web_control

而main中的迭代主要负责一些统计任务。我们主要关心motion的核心——motion_loop。

刷照片的效果实在太挫了，让我们看看如何打开ffmpeg录像的配置。这里需要修改motion-dist.conf中的两个选项(采用默认值则不会录像)：

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# Use ffmpeg to encode a timelapse movie
# Default value 0 = off - else save frame every Nth second
ffmpeg_timelapse 1
# Enables and defines variable bitrate for the ffmpeg encoder.
# ffmpeg_bps is ignored if variable bitrate is enabled.
# Valid values: 0 (default) = fixed bitrate defined by ffmpeg_bps,
# or the range 2 - 31 where 2 means best quality and 31 is worst.
ffmpeg_variable_bitrate 1

第一个选项是设置每一秒保存帧（帧的数量由配置文件中的framerate决定），第二个选项设置ffmpeg编码的比特率。下面还有个选项：

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# Codec to used by ffmpeg for the video compression.
# Timelapse mpegs are always made in mpeg1 format independent from this option.
# Supported formats are: mpeg1 (ffmpeg-0.4.8 only), mpeg4 (default), and msmpeg4.
# mpeg1 - gives you files with extension .mpg
# mpeg4 or msmpeg4 - gives you files with extension .avi
# msmpeg4 is recommended for use with Windows Media Player because
# it requires no installation of codec on the Windows client.
# swf - gives you a flash film with extension .swf
# flv - gives you a flash video with extension .flv
# ffv1 - FF video codec 1 for Lossless Encoding ( experimental )
# mov - QuickTime ( testing )
ffmpeg_video_codec mpeg4

这个其实该不该无所谓，因为编码器的格式在里面是写死的，稍后会提到。motion的录像在motion_loop（motion.c:1698）当中：

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#ifdef HAVE_FFMPEG
if (cnt->conf.timelapse) {
/* Check to see if we should start a new timelapse file. We start one when
* we are on the first shot, and and the seconds are zero. We must use the seconds
* to prevent the timelapse file from getting reset multiple times during the minute.
*/
if (cnt->current_image->timestamp_tm.tm_min == 0 &&
(time_current_frame % 60 < time_last_frame % 60) &&
cnt->shots == 0) {
if (strcasecmp(cnt->conf.timelapse_mode,"manual") == 0) {
;/* No action */
/* If we are daily, raise timelapseend event at midnight */
} else if (strcasecmp(cnt->conf.timelapse_mode, "daily") == 0) { //根据配置文件中ffmpeg_timelapse_mode的选则执行相应代码
if (cnt->current_image->timestamp_tm.tm_hour == 0)
event(cnt, EVENT_TIMELAPSEEND, NULL, NULL, NULL,
&cnt->current_image->timestamp_tm);
/* handle the hourly case */
} else if (strcasecmp(cnt->conf.timelapse_mode, "hourly") == 0) {
event(cnt, EVENT_TIMELAPSEEND, NULL, NULL, NULL,
&cnt->current_image->timestamp_tm);
/* If we are weekly-sunday, raise timelapseend event at midnight on sunday */
} else if (strcasecmp(cnt->conf.timelapse_mode, "weekly-sunday") == 0) {
if (cnt->current_image->timestamp_tm.tm_wday == 0 && cnt->current_image->timestamp_tm.tm_hour == 0)
event(cnt, EVENT_TIMELAPSEEND, NULL, NULL, NULL, &cnt->current_image->timestamp_tm);
/* If we are weekly-monday, raise timelapseend event at midnight on monday */
} else if (strcasecmp(cnt->conf.timelapse_mode, "weekly-monday") == 0) {
if (cnt->current_image->timestamp_tm.tm_wday == 1 && cnt->current_image->timestamp_tm.tm_hour == 0)
event(cnt, EVENT_TIMELAPSEEND, NULL, NULL, NULL, &cnt->current_image->timestamp_tm);
/* If we are monthly, raise timelapseend event at midnight on first day of month */
} else if (strcasecmp(cnt->conf.timelapse_mode, "monthly") == 0) {
if (cnt->current_image->timestamp_tm.tm_mday == 1 && cnt->current_image->timestamp_tm.tm_hour == 0)
event(cnt, EVENT_TIMELAPSEEND, NULL, NULL, NULL, &cnt->current_image->timestamp_tm);
/* If invalid we report in syslog once and continue in manual mode */
} else {
motion_log(LOG_ERR, 0, "Invalid timelapse_mode argument '%s'",
cnt->conf.timelapse_mode);
motion_log(LOG_ERR, 0, "Defaulting to manual timelapse mode");
conf_cmdparse(&cnt, (char *)"ffmpeg_timelapse_mode",(char *)"manual");
}
}
/* If ffmpeg timelapse is enabled and time since epoch MOD ffmpeg_timelaps = 0
* add a timelapse frame to the timelapse mpeg.
*/
if (cnt->shots == 0 &&
time_current_frame % cnt->conf.timelapse <= time_last_frame % cnt->conf.timelapse)
event(cnt, EVENT_TIMELAPSE, cnt->current_image->image, NULL, NULL,
&cnt->current_image->timestamp_tm); // Line:1757 在这里创建并保存录制的视频
} else if (cnt->ffmpeg_timelapse) {
/* if timelapse mpeg is in progress but conf.timelapse is zero then close timelapse file
* This is an important feature that allows manual roll-over of timelapse file using the http
* remote control via a cron job.
*/
event(cnt, EVENT_TIMELAPSEEND, NULL, NULL, NULL, cnt->currenttime_tm);
}
#endif /* HAVE_FFMPEG */

执行录制视频的方法在1757行，根据EVENT_TIMELAPSE，它对应的方法叫event_ffmpeg_timelapse

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// event.c:673
{
EVENT_TIMELAPSE,
event_ffmpeg_timelapse
}，

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// event.c:461
static void event_ffmpeg_timelapse(struct context *cnt,
int type ATTRIBUTE_UNUSED, unsigned char *img,
char *dummy1 ATTRIBUTE_UNUSED, void *dummy2 ATTRIBUTE_UNUSED,
struct tm *currenttime_tm)
{
int width = cnt->imgs.width;
int height = cnt->imgs.height;
unsigned char *convbuf, *y, *u, *v;
if (!cnt->ffmpeg_timelapse) { //只在第一次创建时执行
char tmp[PATH_MAX];
const char *timepath;
/* conf.timepath would normally be defined but if someone deleted it by control interface
it is better to revert to the default than fail */
if (cnt->conf.timepath)
timepath = cnt->conf.timepath;
else
timepath = DEF_TIMEPATH;
mystrftime(cnt, tmp, sizeof(tmp), timepath, currenttime_tm, NULL, 0);
/* PATH_MAX - 4 to allow for .mpg to be appended without overflow */
snprintf(cnt->timelapsefilename, PATH_MAX - 4, "%s/%s", cnt->conf.filepath, tmp);
if (cnt->imgs.type == VIDEO_PALETTE_GREY) {
convbuf = mymalloc((width * height) / 2);
y = img;
u = convbuf;
v = convbuf+(width * height) / 4;
grey2yuv420p(u, v, width, height);
} else {
convbuf = NULL;
y = img;
u = img + width * height;
v = u + (width * height) / 4;
}
if ((cnt->ffmpeg_timelapse =
ffmpeg_open((char *)TIMELAPSE_CODEC, cnt->timelapsefilename, y, u, v, //#define TIMELAPSE_CODEC "mpeg1_tl"
cnt->imgs.width, cnt->imgs.height, 24, cnt->conf.ffmpeg_bps,
cnt->conf.ffmpeg_vbr)) == NULL) { // 创建录像文件
motion_log(LOG_ERR, 1, "ffopen_open error creating (timelapse) file [%s]", cnt->timelapsefilename);
cnt->finish = 1;
return;
}
cnt->ffmpeg_timelapse->udata = convbuf;
event(cnt, EVENT_FILECREATE, NULL, cnt->timelapsefilename, (void *)FTYPE_MPEG_TIMELAPSE, NULL);
}
y = img;
if (cnt->imgs.type == VIDEO_PALETTE_GREY)
u = cnt->ffmpeg_timelapse->udata;
else
u = img + width * height;
v = u + (width * height) / 4;
ffmpeg_put_other_image(cnt->ffmpeg_timelapse, y, u, v); //put图像进录像
}