android4.0 USB Camera實例(五)jpg壓縮

最近大部分時間都在研究usb 攝像頭順便把jpg編碼也寫上　下面大部分函數都是我在網上找的　然後稍微的改一點就可以使用了　不過找這些函數費了不少時間　jpg編碼網上有很多說明　大致流程都是一樣的　我也沒深入研究這裡就不說了　接前面幾篇Camera的文章　這裡主要同把獲取到的yuv數據通過jpg壓縮　以及壓縮成mjpeg視頻流 首先說明下攝像頭獲取到的數據格式是yuv422(p16) 這個是在你初始化攝像頭設置pixelformat我們當初設置的是V4L2_PIX_FMT_YUYV它的實際格式就是yuv422了　具體的格式你就上網找吧　具體過程是　首先將yuv422轉換成rgb888然後在將rgb888轉換成jpg　其實是可以直接將yuv422轉成jpg的但是我沒實現後面我們也放上相關的代碼　下面我就直接上代碼了

首先yuv422轉rgb888

static void YUV422toRGB888(int width, int height, unsigned char *src, unsigned char *dst)
{
	int line, column;
	unsigned char *py, *pu, *pv;
	unsigned char *tmp = dst;
	/* In this format each four bytes is two pixels. Each four bytes is two Y's, aCb 
	and a Cr.Each Y goes to one of the pixels, and the Cb and Cr belong to bothpixels. */
	py = src;
	pu = src + 1;
	pv = src + 3;
	#define CLIP(x) ( (x)>=0xFF ? 0xFF : ( (x) <= 0x00 ? 0x00 : (x) ) )
	for (line = 0; line < height; ++line) {
		for (column = 0; column < width; ++column) {
			*tmp++ = CLIP((double)*py + 1.402*((double)*pv-128.0));
			*tmp++ = CLIP((double)*py - 0.344*((double)*pu-128.0) -0.714*((double)*pv-128.0));
			*tmp++ = CLIP((double)*py + 1.772*((double)*pu-128.0));
			// increase py every time
			py += 2;
			// increase pu,pv every second time
			if ((column & 1)==1) {
				pu += 4;
				pv += 4;
			}
		}
	}
}

然後將rgb888轉成jpg

static int jpeg_mem_copy(unsigned char* img,unsigned char *dest)
{
	struct jpeg_compress_struct cinfo;
	struct jpeg_error_mgr jerr;
	JSAMPROW row_pointer[1];
  	unsigned char *pbuf = NULL;
	int jpglen = 0;
	// create jpeg data
	cinfo.err = jpeg_std_error( &jerr );
	jpeg_create_compress(&cinfo);
	//jpeg_stdio_dest(&cinfo, fp);
	jpeg_mem_dest(&cinfo, &pbuf, &jpglen);
	// set image parameters
	cinfo.image_width = mwidth;
	cinfo.image_height = mheight;
	cinfo.input_components = 3;
	cinfo.in_color_space = JCS_RGB;
	// set jpeg compression parameters to default
	jpeg_set_defaults(&cinfo);
	// and then adjust quality setting
	jpeg_set_quality(&cinfo, 80, TRUE);
	// start compress
	jpeg_start_compress(&cinfo, TRUE);
	// feed data
	while (cinfo.next_scanline < cinfo.image_height) {
		row_pointer[0] = &img[cinfo.next_scanline * cinfo.image_width * 
		cinfo.input_components];
		jpeg_write_scanlines(&cinfo, row_pointer, 1);
	}
	// finish compression
	jpeg_finish_compress(&cinfo);
	// destroy jpeg data
	jpeg_destroy_compress(&cinfo);
    memcpy(dest,pbuf,jpglen);
	//LOGD("++++++++++++++++len is %d\n",jpglen);
	if(pbuf)
		free(pbuf);
    return jpglen;
}

這裡我使用的是最新的jpeg庫9a的裡面已經集成了jpeg_mem_dest函數 libjpeg移植網上也有很多說明

下面是我提供給上層調用的一個接口

JNIEXPORT jint JNICALL Java_com_hclydao_usbcamera_Fimcgzsd_writefile(JNIEnv * env, jclass obj,jbyteArray yuvdata,jbyteArray filename)//jintArray rgbdata
{
	jbyte *ydata = (jbyte*)(*env)->GetByteArrayElements(env, yuvdata, 0);
	jbyte *filedir = (jbyte*)(*env)->GetByteArrayElements(env, filename, 0);

	FILE * outfile;
  	if ((outfile = fopen(filedir, "wb")) == NULL) {
    	LOGE("++++++++++++open %s failed\n",filedir);
    	return -1;
  	}
	//yuv422_to_jpeg(ydata,mwidth,mheight,outfile,80);
	unsigned char* src = (unsigned char*)ydata;
	unsigned char* dst = malloc(mwidth*mheight*3*sizeof(char));
	unsigned char* jpgdata = malloc(mwidth*mheight*3*sizeof(char));
	YUV422toRGB888(mwidth,mheight,src,dst);
	int size=jpeg_mem_copy(dst,jpgdata);
	fwrite(jpgdata,size,1,outfile);
	if(dst)free(dst);
	if(jpgdata)free(jpgdata);
	fclose(outfile);
	(*env)->ReleaseByteArrayElements(env, yuvdata, ydata, 0);
	(*env)->ReleaseByteArrayElements(env, filename, filedir, 0);
}

這個傳入的是獲取到的yuv數據以及要保存的jpg文件的路徑 裡面有一些參數是我聲明的全局變量　具體可以去看我前面幾篇文章

以下是視頻流的相關接口

FILE * video_file;
/*
 *put in frame buffer to queue
 */
JNIEXPORT jint JNICALL Java_com_hclydao_usbcamera_Fimcgzsd_videoopen(JNIEnv * env, jclass obj,jbyteArray filename)
{
	jbyte *filedir = (jbyte*)(*env)->GetByteArrayElements(env, filename, 0);

  	if ((video_file = fopen(filedir, "wb")) == NULL) {
    	LOGE("++++++++++++open %s failed\n",filedir);
    	return -1;
  	}

	(*env)->ReleaseByteArrayElements(env, filename, filedir, 0);
}

JNIEXPORT jint JNICALL Java_com_hclydao_usbcamera_Fimcgzsd_videostart(JNIEnv * env, jclass obj,jbyteArray yuvdata)
{
	jbyte *ydata = (jbyte*)(*env)->GetByteArrayElements(env, yuvdata, 0);
	unsigned char* src = (unsigned char*)ydata;
	unsigned char* dst = malloc(mwidth*mheight*3*sizeof(char));
	unsigned char* jpgdata = malloc(mwidth*mheight*3*sizeof(char));
	YUV422toRGB888(mwidth,mheight,src,dst);
	int size=jpeg_mem_copy(dst,jpgdata);
	fwrite(jpgdata,size,1,video_file);
	//fwrite(dst,(mwidth*mheight*3*sizeof(char)),1,video_file);
	if(dst)free(dst);
	if(jpgdata)free(jpgdata);
	(*env)->ReleaseByteArrayElements(env, yuvdata, ydata, 0);
}

JNIEXPORT jint JNICALL Java_com_hclydao_usbcamera_Fimcgzsd_videoclose(JNIEnv * env, jclass obj)
{
	fclose(video_file);
}

就是連續保存jpg文件到同一個文件 保存的文件直接播放不了　用格式工廠轉換成avi以後就可以放了

下面是一個直接將yuv轉jpg的函數　這是將yuv420p轉成jpg的 我的是yuv422的　改了很多次發現保存的圖片不對　看來還是要研究下這些格式之間的區別

/* put_jpeg_yuv420p_memory converts an input image in the YUV420P format into a jpeg image and puts
 * it in a memory buffer.
 * Inputs:
 * - input_image is the image in YUV420P format.
 * - width and height are the dimensions of the image
 * Output:
 * - dest_image is a pointer to the jpeg image buffer
 * Returns buffer size of jpeg image     
 */
static int put_jpeg_yuv420p_memory(unsigned char *dest_image,
                                   unsigned char *input_image, int width, int height)
{
    int i, j, jpeg_image_size;
  
    JSAMPROW y[16],cb[16],cr[16]; // y[2][5] = color sample of row 2 and pixel column 5; (one plane)
    JSAMPARRAY data[3]; // t[0][2][5] = color sample 0 of row 2 and column 5
  
    struct jpeg_compress_struct cinfo;
    struct jpeg_error_mgr jerr;
  	char *pbuf = NULL;
	int jpglen = 0;
    data[0] = y;
    data[1] = cb;
    data[2] = cr;
  
    cinfo.err = jpeg_std_error(&jerr);  // errors get written to stderr 
      
    jpeg_create_compress(&cinfo);
    cinfo.image_width = width;
    cinfo.image_height = height;
    cinfo.input_components = 3;
    jpeg_set_defaults (&cinfo);
  
    jpeg_set_colorspace(&cinfo, JCS_YCbCr);
  
    cinfo.raw_data_in = TRUE;                  // supply downsampled data
    cinfo.do_fancy_downsampling = FALSE;       // fix segfaulst with v7
    cinfo.comp_info[0].h_samp_factor = 2;
    cinfo.comp_info[0].v_samp_factor = 2;
    cinfo.comp_info[1].h_samp_factor = 1;
    cinfo.comp_info[1].v_samp_factor = 1;
    cinfo.comp_info[2].h_samp_factor = 1;
    cinfo.comp_info[2].v_samp_factor = 1;
  
    jpeg_set_quality(&cinfo, 80, TRUE);
    cinfo.dct_method = JDCT_FASTEST;
  
    jpeg_mem_dest(&cinfo, &pbuf, &jpglen);    // data written to mem
      
    jpeg_start_compress (&cinfo, TRUE);
  
    for (j = 0; j < height; j += 16) {
        for (i = 0; i < 16; i++) {
            y[i] = input_image + width * (i + j);
            if (i%2 == 0) {
                cb[i/2] = input_image + width * height + width / 2 * ((i + j) / 2);
                cr[i/2] = input_image + width * height + width * height / 4 + width / 2 * ((i + j) / 2);
            }
        }
        jpeg_write_raw_data(&cinfo, data, 16);
    }
  
    jpeg_finish_compress(&cinfo);
    jpeg_destroy_compress(&cinfo);
    memcpy(dest_image,pbuf,jpglen);
	if(pbuf)
		free(pbuf);
    return jpglen;
}

最近比較迷茫　所以沒有深入研究這些　同時我也一直在想　有些東西到底有沒有深入研究的必要　糾結　接下來接著准備看下ffmpeg h264壓縮