作者：曹忠明,华清远见嵌入式学院讲师。
一、环境
主机环境 ：ubuntu 10.10
目标机 ：FS2410(S3C2410)
主机工具链 ：gcc-4.4.5
交叉工具链 ：arm-none-linux-gnueabi-gcc-4.3.2
摄像头 ：ZC301
二、移植过程
1、配置内核是内核支持芯片为ZC301的摄像头
Make menuconfig
Device Drivers --->
<*> Multimedia support --->
<*> Video For Linux
[*] Enable Video For Linux API 1 (DEPRECATED) (NEW)
[*] Video capture adapters (NEW) --->
[*] V4L USB devices (NEW) --->
<*> USB Video Class (UVC)
[*] UVC input events device support (NEW)
<*> USB ZC0301[P] webcam support (DEPRECATED)
2、重新编译内核
make zImage
通过上面两个步骤就可以驱动我们的摄像头了。但是这个驱动是基于V4l2的。以前基于 V4L的一些上层应用就不能用了，或需要做大量的修改！这里我们要实现网络视频的功能，以前都是用servfox这个网络视频服务器，但是这个服务器就是 基于V4L的，我们如果想用的话就得对servfox的源码进行修改。这里我们选用另外一种方案mjpg-stream。
3、mjpg-stream的移植
关于mjpg-stream的资料大家可以在下面这个网址查看：http://sourceforge.net/apps/mediawiki/mjpg-streamer/index.php?title=Main_Page
mjpg-stream的移植需要jpeg的库，所以我们先移植jpeg的库
(1)jpeg库的移植
1)jpeg源码包通过下面这个网址下载
http://www.ijg.org/files/jpegsrc.v8b.tar.gz
2)解压源码包
tar xvf jpegsrc.v8b.tar.gz
3)配置源码
cd jpeg-8b
./configure --prefix=/home/linux/s3c2410-2.6.35/video/jpeg --host=arm-none-linux-gnueabi
4)编译
make
5)安装
make install
6)拷贝库到文件系统中
cp //home/linux/s3c2410-2.6.35/video/jpeg /lib/libjpeg.so.8 /source/rootfs/lib
(2)mjpg-stream的移植
1)mjpg-stream源码包通过下面这个网址下载
http://sourceforge.net/projects/mjpg-streamer/
2)解压源码
tar xvf mjpg-streamer-r63.tar.gz
3)修改源码
cd mjpg-streamer-r63
修改顶层makefile及plugins目录中的各级makefile将所有
CC=gcc
修改为
CC=arm-none-linux-gnueabi-gcc【arm-linux-gcc】
修改plugins/input_uvc/Makfile
修改
CFLAGS += -O2 -DLINUX -D_GNU_SOURCE -Wall -shared -fPIC
为
CFLAGS += -O2 -DLINUX -D_GNU_SOURCE -Wall -shared -fPIC -I/home/linux/s3c2410-2.6.35/video/jpeg/include
修改
$(CC) $(CFLAGS) -ljpeg -o $@ input_uvc.c v4l2uvc.lo jpeg_utils.lo dynctrl.lo
为
$(CC) $(CFLAGS) -ljpeg -L/home/linux/s3c2410-2.6.35/video/jpeg/lib -o $@ input_uvc.c v4l2uvc.lo jpeg_utils.lo dynctrl.lo
jpeg_utils.c:27: fatal error: jpeglib.h: No such file or directory
4)编译
make
5)测试
mkdir /source/rootfs/mjpg
cp *.so /source/rootfs/mjpg
cp mjpg-stream /source/rootfs/bin
把*.so www文件夹 可执行文件mjpg_streamer start.sh复制到一个新建目录mjpg，然后把mjpg复制到开发板
mkdir ./mjpg
cp *.so start.sh ./mjpg
cp -r www ./mjpg
打开开开发板运行
mjpg_streamer -i "/mjpg/input_uvc.so" -o "/mjpg/output_http.so -w /www"
在源码目录下有start.sh,这个脚本里有一些mjpg-stream的使用方法及说明
http://192.168.1.202:8080/?action=stream
打开一个网页输入下面地址就能够看到一个静态图片：
http://192.168.1.202:8080/?action=snapshot
6)在mjpg源码下有一个www的目录，这个一个网络使用mjpg的实例，结合web服务器(boa)可以实现一些其他相关功能。
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过程记录：
下载的 mjpg-streamer-r63.tar.gz
编译完成
执行命令 mjpg_streamer 出现下面错误
MJPG-streamer [525]: starting application
MJPG Streamer Version.: 2.0
MJPG-streamer [525]: MJPG Streamer Version.: 2.0
ERROR: could not find input plugin
MJPG-streamer [525]: ERROR: could not find input plugin
Perhaps you want to adjust the search path with:
MJPG-streamer [525]: Perhaps you want to adjust the search path with:
# export LD_LIBRARY_PATH=/path/to/plugin/folder
MJPG-streamer [525]: # export LD_LIBRARY_PATH=/path/to/plugin/folder
dlopen: input_uvc.so: cannot open shared object file: No such file or directory
MJPG-streamer [525]: dlopen: input_uvc.so: cannot open shared object file: No such。。。
原因及解决办法
这是找不到共享造成的。Linux和windows不一样，不会在可执行文件所在的目录搜索 共享库文件。解决办法：敲入如下命令：export LD_LIBRARY_PATH=/mjpg-streamer-r63:$LD_LIBRARY_PATH (我的共享库.so文件时放在/mjpg-streamer-r63目录里)，设定共享库的搜索路径就可以了！
执行命令
./mjpg_streamer -o "output_http.so -w ./www" -i "input_uvc.so -y -d /dev/video0"
执行成功
输入网址
http://192.168.1.6:8080/?action=index.html
注意 命令参考start.sh，如
mkdir pics
./mjpg_streamer -o "output_http.so -w `pwd`/www" -o "output_file.so -f pics -d 15000"
每隔15秒存储一张图片。
#该命令由于程序默认是MJPG的，故只有MJPG摄像头有用，对输出yuyv格式的摄像头无效
./mjpg_streamer -o "output_http.so -w ./www"
#该命令参数-y指定yuyv摄像头，enable YUYV format and disable MJPEG mode
#./mjpg_streamer -o "output_http.so -w ./www" -i "input_uvc.so -y -d /dev/video0"
-----------------------------------------------------------------------
-----------------------------------------------------------------------
命令
./mjpg_streamer --help
Usage: ./mjpg_streamer
-i | --input "<input-plugin.so> [parameters]"
-o | --output "<output-plugin.so> [parameters]"
[-h | --help ]........: display this help
[-v | --version ].....: display version information
[-b | --background]...: fork to the background, daemon mode
-----------------------------------------------------------------------
Example #1:
To open an UVC webcam "/dev/video1" and stream it via HTTP:
./mjpg_streamer -i "input_uvc.so -d /dev/video1" -o "output_http.so"
-----------------------------------------------------------------------
Example #2:
To open an UVC webcam and stream via HTTP port 8090:
./mjpg_streamer -i "input_uvc.so" -o "output_http.so -p 8090"
-----------------------------------------------------------------------
Example #3:
To get help for a certain input plugin:
./mjpg_streamer -i "input_uvc.so --help"
-----------------------------------------------------------------------
In case the modules (=plugins) can not be found:
* Set the default search path for the modules with:
export LD_LIBRARY_PATH=/path/to/plugins,
* or put the plugins into the "/lib/" or "/usr/lib" folder,
* or instead of just providing the plugin file name, use a complete
path and filename:
./mjpg_streamer -i "/path/to/modules/input_uvc.so"
-----------------------------------------------------------------------
-----------------------------------------------------------------------
命令
./mjpg_streamer -i "input_uvc.so --help"
MJPG-streamer [1177]: starting application
MJPG Streamer Version.: 2.0
MJPG-streamer [1177]: MJPG Streamer Version.: 2.0
---------------------------------------------------------------
Help for input plugin..: UVC webcam grabber
---------------------------------------------------------------
The following parameters can be passed to this plugin:
[-d | --device ].......: video device to open (your camera)
[-r | --resolution ]...: the resolution of the video device,
can be one of the following strings:
QSIF QCIF CGA QVGA CIF VGA
SVGA XGA SXGA
or a custom value like the following
example: 640x480
[-f | --fps ]..........: frames per second
[-y | --yuv ]..........: enable YUYV format and disable MJPEG mode
[-q | --quality ]......: JPEG compression quality in percent
(activates YUYV format, disables MJPEG)
[-m | --minimum_size ].: drop frames smaller then this limit, useful
if the webcam produces small-sized garbage frames
may happen under low light conditions
[-n | --no_dynctrl ]...: do not initalize dynctrls of Linux-UVC driver
[-l | --led ]..........: switch the LED "on", "off", let it "blink" or leave
it up to the driver using the value "auto"
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