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 Android教程網 >> Android技術 >> 關於Android編程 >> android4.0 USB Camera實例(一)HAL層

android4.0 USB Camera實例(一)HAL層

編輯：關於Android編程

一直想自己寫一個從HAL層到應用層的Camera例子，android4.0上usb camera用不了 所以決定自己寫一個 usb camera和coms原理都是一樣的 基本v4l2 只不過源碼數據格式不一樣而已 下面我們就從HAL層開始

以下是我的代碼，先上代碼在 一步步說明

fimcgzsd.c

/*
 * Android USB Camera zc3xx Library
 *
 * Copyright (c) 2014  Store information technology guangzhou ltd
 * Copyright (c) 2014  hclydao 
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License.
 */
#include 
#include 	
#include 	
#include 
#include 
#include     
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define  LOG_TAG    "FimcGzsd"
#define LOGV(...) __android_log_print(ANDROID_LOG_VERBOSE, LOG_TAG, __VA_ARGS__)
#define LOGD(...) __android_log_print(ANDROID_LOG_DEBUG  , LOG_TAG, __VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO   , LOG_TAG, __VA_ARGS__)
#define LOGW(...) __android_log_print(ANDROID_LOG_WARN   , LOG_TAG, __VA_ARGS__)
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR  , LOG_TAG, __VA_ARGS__)

struct fimc_buffer {
    unsigned char *start;
    size_t  length;
};

static int fd = -1;
struct fimc_buffer *buffers=NULL;
struct v4l2_buffer v4l2_buf;
static int bufnum = 1;
static int mwidth,mheight;
/*
 *open usb camera device
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_open(JNIEnv * env, jclass obj, const jbyteArray devname)
{
	jbyte *dev = (jbyte*)(*env)->GetByteArrayElements(env, devname, 0);
	fd = open(dev, O_RDWR, 0);  
	if (fd<0)
	{
		LOGE("%s ++++ open error\n",dev);
		return  -1;
	}
	(*env)->ReleaseByteArrayElements(env, devname, dev, 0);
	return fd;
}
/*
 * init device
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_init(JNIEnv * env, jclass obj, jint width, jint height,jint numbuf)
{
	int ret;
	int i;
	bufnum = numbuf;
	mwidth = width;
	mheight = height;
	struct v4l2_format fmt;	
	struct v4l2_capability cap;

    ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);
    if (ret < 0) {
        LOGE("%d :VIDIOC_QUERYCAP failed\n",__LINE__);
        return -1;
    }
    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        LOGE("%d : no capture devices\n",__LINE__);
        return -1;
    }
				
	memset( &fmt, 0, sizeof(fmt));
	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB565;
	fmt.fmt.pix.width = width;
	fmt.fmt.pix.height = height;					
	if (ioctl(fd, VIDIOC_S_FMT, &fmt) < 0)
	{
		LOGE("++++%d : set format failed\n",__LINE__);
		return -1;
	}

    struct v4l2_requestbuffers req;
    req.count = numbuf;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(fd, VIDIOC_REQBUFS, &req);
    if (ret < 0) {
        LOGE("++++%d : VIDIOC_REQBUFS failed\n",__LINE__);
        return -1;
    }

    buffers = calloc(req.count, sizeof(*buffers));
    if (!buffers) {
        LOGE ("++++%d Out of memory\n",__LINE__);
		return -1;
    }

	for(i = 0; i< bufnum; ++i) {
		memset(&v4l2_buf, 0, sizeof(v4l2_buf));
		v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
		v4l2_buf.memory = V4L2_MEMORY_MMAP;
		v4l2_buf.index = i;
		ret = ioctl(fd , VIDIOC_QUERYBUF, &v4l2_buf);
		if(ret < 0) {
		   LOGE("+++%d : VIDIOC_QUERYBUF failed\n",__LINE__);
		   return -1;
		}
		buffers[i].length = v4l2_buf.length;
		if ((buffers[i].start = (char *)mmap(0, v4l2_buf.length,
		                                     PROT_READ | PROT_WRITE, MAP_SHARED,
		                                     fd, v4l2_buf.m.offset)) < 0) {
		     LOGE("%d : mmap() failed",__LINE__);
		     return -1;
		}
	}
	return 0;
}
/*
 *open usb camera device
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_streamon(JNIEnv * env, jclass obj)
{
	int i;
	int ret;
	enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	for(i = 0; i< bufnum; ++i) {
		memset(&v4l2_buf, 0, sizeof(v4l2_buf));
		v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
		v4l2_buf.memory = V4L2_MEMORY_MMAP;
		v4l2_buf.index = i;
		ret = ioctl(fd, VIDIOC_QBUF, &v4l2_buf);
		if (ret < 0) {
		    LOGE("%d : VIDIOC_QBUF failed\n",__LINE__);
		    return ret;
		}
	}
    ret = ioctl(fd, VIDIOC_STREAMON, &type);
    if (ret < 0) {
        LOGE("%d : VIDIOC_STREAMON failed\n",__LINE__);
        return ret;
    }
	return 0;
}
/*
 *get one frame data
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_dqbuf(JNIEnv * env, jclass obj,const jbyteArray videodata)
{
    int ret;

	jbyte *data = (jbyte*)(*env)->GetByteArrayElements(env, videodata, 0);
    v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    v4l2_buf.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(fd, VIDIOC_DQBUF, &v4l2_buf);
    if (ret < 0) {
        LOGE("%s : VIDIOC_DQBUF failed, dropped frame\n",__func__);
        return ret;
    }

	memcpy(data,buffers[v4l2_buf.index].start,buffers[v4l2_buf.index].length);
	(*env)->ReleaseByteArrayElements(env, videodata, data, 0);
	return v4l2_buf.index;
}
/*
 *put in frame buffer to queue
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_qbuf(JNIEnv * env, jclass obj,jint index)
{
    int ret;

    v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    v4l2_buf.memory = V4L2_MEMORY_MMAP;
    v4l2_buf.index = index;

    ret = ioctl(fd, VIDIOC_QBUF, &v4l2_buf);
    if (ret < 0) {
        LOGE("%s : VIDIOC_QBUF failed\n",__func__);
        return ret;
    }

    return 0;
}
/*
 *streamoff
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_streamoff(JNIEnv * env, jclass obj,jint index)
{
    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    int ret;

    ret = ioctl(fd, VIDIOC_STREAMOFF, &type);
    if (ret < 0) {
        LOGE("%s : VIDIOC_STREAMOFF failed\n",__func__);
        return ret;
    }

    return 0;
}
/*
 *release
 */
JNIEXPORT jint JNICALL Java_com_dao_usbcam_Fimcgzsd_release(JNIEnv * env, jclass obj)
{
    enum v4l2_buf_type type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    int ret;
	int i;

    ret = ioctl(fd, VIDIOC_STREAMOFF, &type);
    if (ret < 0) {
        LOGE("%s : VIDIOC_STREAMOFF failed\n",__func__);
        return ret;
    }

    for (i = 0; i < bufnum; i++) {
       ret = munmap(buffers[i].start, buffers[i].length);
		if (ret < 0) {
		    LOGE("%s : munmap failed\n",__func__);
		    return ret;
    	}
	}
	free (buffers);
	close(fd);
	return 0;
}

首先是open這個就不作說明了

第二初始化init函數

    ret = ioctl(fd, VIDIOC_QUERYCAP, &cap);
    if (ret < 0) {
        LOGE("%d :VIDIOC_QUERYCAP failed\n",__LINE__);
        return -1;
    }
    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
        LOGE("%d : no capture devices\n",__LINE__);
        return -1;
    }
獲取設備相關信息，檢查是否支持capture模式

	memset( &fmt, 0, sizeof(fmt));
	fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
	fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_RGB565;
	fmt.fmt.pix.width = width;
	fmt.fmt.pix.height = height;					
	if (ioctl(fd, VIDIOC_S_FMT, &fmt) < 0)
	{
		LOGE("++++%d : set format failed\n",__LINE__);
		return -1;
	}
設置格式,usb camera獲取到的已經是jpeg格式 所以這裡設置成RGB565格式

    struct v4l2_requestbuffers req;
    req.count = numbuf;
    req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    req.memory = V4L2_MEMORY_MMAP;

    ret = ioctl(fd, VIDIOC_REQBUFS, &req);
    if (ret < 0) {
        LOGE("++++%d : VIDIOC_REQBUFS failed\n",__LINE__);
        return -1;
    }
申請緩沖區,這裡申請numbuf個緩沖幀
    buffers = calloc(req.count, sizeof(*buffers));
    if (!buffers) {
        LOGE ("++++%d Out of memory\n",__LINE__);
		return -1;
    }

	for(i = 0; i< bufnum; ++i) {
		memset(&v4l2_buf, 0, sizeof(v4l2_buf));
		v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
		v4l2_buf.memory = V4L2_MEMORY_MMAP;
		v4l2_buf.index = i;
		ret = ioctl(fd , VIDIOC_QUERYBUF, &v4l2_buf);
		if(ret < 0) {
		   LOGE("+++%d : VIDIOC_QUERYBUF failed\n",__LINE__);
		   return -1;
		}
		buffers[i].length = v4l2_buf.length;
		if ((buffers[i].start = (char *)mmap(0, v4l2_buf.length,
		                                     PROT_READ | PROT_WRITE, MAP_SHARED,
		                                     fd, v4l2_buf.m.offset)) < 0) {
		     LOGE("%d : mmap() failed",__LINE__);
		     return -1;
		}
	}
映射虛擬內存到物理地址，獲取每個緩沖區的物理地址


streamon函數

將緩沖區放入隊列並開啟數據流

dqbuf函數

獲取一幀數據 返回當前緩沖區的序列號

qbuf函數

將指定緩沖區放入隊列，獲取到某一緩沖區的數據後需要重新將這個緩沖區放入隊列

後面兩個我就不多說明了


Android.mk文件:

LOCAL_PATH:= $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := eng
LOCAL_SRC_FILES:= fimcgzsd.c
LOCAL_MODULE := libfimcgzsd
LOCAL_LDLIBS    := -llog
LOCAL_SHARED_LIBRARIES := libc libcutils
include $(BUILD_SHARED_LIBRARY)



參考博文:http://blog.csdn.net/eastmoon502136/article/details/8190262

============================================
作者：hclydao
http://blog.csdn.net/hclydao
版權沒有，但是轉載請保留此段聲明

============================================


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