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GenICam 标准

下载：https://www.emva.org/standards-technology/genicam/genicam-downloads/

GigE Vision 协议

https://en.wikipedia.org/wiki/GigE_Vision
https://www.automate.org/vision/vision-standards/vision-standards-gige-vision
设备发现机制：GVCP Device Discovery
- 使用UDP广播，不能跨路由，所以只限定同一局域网 a “limited broadcast” by RFC1122
- Definitions of broadcast types are provided in section 3.3.6 of RFC1122
- In GigE Vision 1.x, GVCP is only defined to listen on UDP port 3956.
- GigE Vision version 2.0 defines how devices can advertise and discover each other using a combination of multicast DNS and DNS-SD, called Zeroconf Discovery
A GigE Vision device MUST have an XML device description file with the syntax described in the GenApi module of the GenICam standard
- The filename of the XML device description file MUST be different when the file content changes.

GVCP

GVCP是一种基于UDP传输层协议的应用层协议，此控制协议不包括GigE视觉流媒体协议（GVSP）。
控制设备的连接是唯一的，读取的连接可以多个
GVCP 的 IP头固定为20字节，不使用 IP 头可选项（linux socket 就是默认不使用）
The first GVCP port of the device MUST use UDP port 3956.This standard GVCP port has been registered with IANA (http://www.iana.org/assignments/port-numbers).
GVCP, 命令（command）和确认（ack）消息包含在同一个包中，这样能确保包不用碎片化分割，同理，GVCP的包大小不能超过 576 字节，因为可避免IP碎片化的最大传输单元（MTU）为576字节
一个GVCP包的结构大小：

Layer Size(in bytes)

IP header (options not allowed) 20

UDP header 8

GVCP header 8

Max. GVCP payload 540

Total 576
GVCP 包必须32位对齐，header已满足条件，即要求有效载荷payload部分必须4字节对齐
应用获取设备确认消息超时后，必须重发命令消息，重发命令消息时 req_id 保持不变
重传消息默认是 200 ms 超时，次数3，这两个值都应可设置
req_id 初始值不能为0，由应用端按命令消息递增
设备端的 ack_id 返回与命令消息一一对应，即重复的命令也会重复返回（但可能不会重复执行），应用端需处理收到多次同一 ack_id 消息的情况
应用端必须忽略 ack_id 不匹配的消息，应用端必须收到前一条命令的ack确认消息后才能发送下一条命令（除了 DISCOVERY_CMD, PACKETRESEND_CMD）
应用端要确保心跳连接。设备提供一个Heartbeat Timeout启动寄存器。建议应用端在该设备心跳超时时间内发送三次心跳消息，避免连接被设备端自动关闭
GVCP header 头结构：第一字节值固定 0x42

Layer	Size(in bytes)
IP header (options not allowed)	20
UDP header	8
GVCP header	8
Max. GVCP payload	540
Total	576

命令头结构 Command Messaeg Header

COMMAND MESSAGE HEADER
0x42	8 bits	Hard-coded key code value used for message validation.
flag	8 bits	Upper 4 bits (msb, bit 0 to bit 3) are specific to each GVCP commands.
^^	^^	Lower 4 bits (lsb, bit 4 to bit 7) are common to all GVCP commands.
^^	^^	All unused bits must be set to 0.
^^	^^	bit 0 to 3 – Specific to each command. Set to 0 if the command does not use them.
^^	^^	bit 4 – Reserved, set to 0 on transmission, ignore on reception.
^^	^^	bit 5 – Reserved, set to 0 on transmission, ignore on reception.
^^	^^	bit 6 – Reserved, set to 0 on transmission, ignore on reception.
^^	^^	bit 7 – ACKNOWLEDGE:
^^	^^	SET = 要求接收者必须发送 ack 确认消息.
^^	^^	CLEAR = 接收者不应发送 ack 确认消息.
^^	^^	ACKNOWLEDGE 的优先级比命令本身是否需要回复的优先级要高
command	16 bits	Command message value (see dictionary section).
^^	^^	Commands from 0 to 32765 are reserved for GigE Vision. Others are available for customization (device-specific).
length	16 bits	负载 payload 的字节数，不包括头长度
req_id	16 bits	递增的 req_id, 非0，应用端提供，设备端回复 ack_id 时拷贝相同值

ACK 消息头结构：

ACKNOWLEDGE MESSAGE HEADER
status	16 bits	Status of the requested operation (see status code section)
acknowledge	16 bits	Acknowledge message value (see dictionary section).
length	16 bits	头之后的负载的字节数
ack_id	16 bits	值与所响应的命令消息的req_id 相同

GVCP必须使用网络字节顺序，即大端序 big-endian

DISCOVERY

DISCOVERY_CMD 值 0x0002
命令消息头 flag 的 bit3 指示设备是否广播 DISCOVER_ACK 消息
命令消息头 flag 的 bit7 必定设置为1，即设备端必须回复 ack 消息

DISCOVERY_ACK 值 0x0003 , 回复消息的头与负载结构(每行4字节，除了标明长度的）：

0	1	2	3
status		answer = DISCOVERY_ACK
length		ack_id
spec_version_major		spec_version_minor
device_mode
reserved		device_MAC_address (high)
device_MAC_address (low)
IP_config_options
IP_config_current
reserved
reserved
reserved
current_IP
reserved
reserved
reserved
current_subnet_mask
reserved
reserved
reserved
default_gateway
manufacturer_name [32 bytes]
model_name [32 bytes]
device_version [32 bytes]
manufacturer_specific_information [48 bytes]
serial_number [16 bytes]
user_defined_name [16 bytes]

测试代码：

#include <iostream>
#include <cstring>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
 
#include <iomanip>
 
#define BROADCAST_PORT 3956 // GigE Vision discovery port
#define BUFFER_SIZE 1024
 
int main() {
    int sock;
    struct sockaddr_in broadcastAddr;
    char broadcastBuffer[BUFFER_SIZE];
    int broadcastPermission;
    unsigned int sendLen;
 
    // 创建UDP套接字
    sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sock < 0) {
        std::cerr << "Socket creation failed." << std::endl;
        return -1;
    }
 
    // 设置广播权限
    broadcastPermission = 1;
    if (setsockopt(sock, SOL_SOCKET, SO_BROADCAST, (void *) &broadcastPermission, sizeof(broadcastPermission)) < 0) {
        std::cerr << "Setting socket option to SO_BROADCAST failed." << std::endl;
        close(sock);
        return -1;
    }
 
    // 设置广播地址
    memset(&broadcastAddr, 0, sizeof(broadcastAddr));
    broadcastAddr.sin_family = AF_INET;
    broadcastAddr.sin_addr.s_addr = inet_addr("255.255.255.255"); // 广播地址
    broadcastAddr.sin_port = htons(BROADCAST_PORT);
 
    // 构造广播消息（这里简化了，实际应该按照GigE Vision协议构造）
    uint8_t discovery_msg[8] = {0};
    discovery_msg[0] = 0x42;
    discovery_msg[1] = 0x80;
    discovery_msg[2] = 0;
    discovery_msg[3] = 0x02; // DISCOVERY_CMD: 0x0002
    discovery_msg[4] = 0;
    discovery_msg[5] = 0;    // length 0
    discovery_msg[6] = 0;
    discovery_msg[7] = 1;    // req_id 1
 
    const size_t send_len = 8;
    // 发送广播消息
    if (sendto(sock, discovery_msg, send_len, 0, (struct sockaddr *) &broadcastAddr, sizeof(broadcastAddr)) != send_len) {
        std::cerr << "Broadcast sendto() failed." << std::endl;
        close(sock);
        return -1;
    }
 
    std::cout << "Broadcast message sent. Waiting for responses..." << std::endl;
 
    // 接收响应（这里简化了，实际应该处理多个响应，并解析GigE Vision协议数据）
    struct sockaddr_in recvAddr;
    socklen_t addrLen = sizeof(recvAddr);
    int recvLen = recvfrom(sock, broadcastBuffer, BUFFER_SIZE, 0, (struct sockaddr *) &recvAddr, &addrLen);
 
    if (recvLen > 0) {
        broadcastBuffer[recvLen] = '\0';
        std::cout << "Received a response from: " << inet_ntoa(recvAddr.sin_addr) << std::endl;
        std::cout << "Size: " << recvLen << std::endl;
 
        std::cout << "Response: " << std::hex << std::setfill('0') << std::setw(2) << std::showbase;
 
        for (int i = 0; i < recvLen; ++i) {
            if (i >= 80 && broadcastBuffer[i] > 32 && broadcastBuffer[i] < 127) {
                std::cout << broadcastBuffer[i] << " ";
            } else {
                std::cout << (int)(broadcastBuffer[i]) << " ";
            }
 
            if (i > 0 && ((i+1) % 16 == 0)) {
                std::cout << std::endl;
            }
        }
 
        std::cout << std::endl;
 
        char mac[7] = {0};
        memcpy(mac, broadcastBuffer + 18, 6);
 
        char ip[4] = {0};
        memcpy(ip, broadcastBuffer + 44, 4);
 
        char manufacturer_name[33] = {0};
        memcpy(manufacturer_name, broadcastBuffer + 80, 32);
        char model_name[33] = {0};
        memcpy(model_name, broadcastBuffer + 80 + 32, 32);
        char device_version[33] = {0};
        memcpy(device_version, broadcastBuffer + 80 + 64, 32);
        char manufacturer_spec_info[49] = {0};
        memcpy(manufacturer_spec_info, broadcastBuffer + 80 + 96, 48);
        char serial_number[17] = {0};
        memcpy(serial_number, broadcastBuffer + 80 + 96 + 48, 16);
        char user_defined_name[17] = {0};
        memcpy(user_defined_name, broadcastBuffer + 80 + 96 + 48 + 16, 16);
 
        std::cout << std::noshowbase << "mac: "
            << (int)(mac[0]) << ":"
            << (int)(mac[1]) << ":"
            << (int)(mac[2]) << ":"
            << (int)(mac[3]) << ":"
            << (int)(mac[4]) << ":"
            << (int)(mac[5]) << std::endl;
        std::cout << std::dec << std::setw(0) <<  "ip: "
            << (int)(ip[0]) << "."
            << (int)(ip[1]) << "."
            << (int)(ip[2]) << "."
            << (int)(ip[3]) << std::endl;
        std::cout << "manufacturer_name : " << manufacturer_name << std::endl;
        std::cout << "model_name : " << model_name << std::endl;
        std::cout << "device_version : " << device_version << std::endl;
        std::cout << "manufacturer_spec_info : " << manufacturer_spec_info << std::endl;
        std::cout << "serial_number : " << serial_number << std::endl;
        std::cout << "user_defined_name : " << user_defined_name << std::endl;
 
    } else {
        std::cerr << "No response received, or recvfrom() failed." << std::endl;
    }
    // 关闭套接字
    close(sock);
    return 0;
}

FORCEIP

FORCEIP_CMD （0x0004）可以强制修改静态IP，
- 前提1：知道相机的MAC地址
- 前提2：相机当前没有控制应用端连接

channel 概念

通道(channel)概念：A channel is a virtual link used to transfer information between GigE Vision entities. GigE Vision supports three types of channels:
1. Control channel (there is always 1 control channel for the primary application)
2. Stream channel (from 0 to 512 stream channels)
3. Message channel (0 or 1 message channel)
除了 3965 用于控制通道端口，其它通道可用任何端口
GVCP 定义了4级权限
- Exclusive access: 独占权限，当应用程序具有独占访问权限时，设备不能允许第二个应用创建控制通道
- Control access：控制权限，当应用程序具有控制权限时，设备可以允许第二个应用端具有读取权限
- Control access with switchover enabled：可切换的控制权限，设备允许第二个具有正确凭据的应用端拥有控制权限
- Monitor access：监视权限，如果设备当前没有独占权限的应用端连接就可以使用
- 一个设备只支持独占访问是完全合法的
- 备忘：14.4节讲述怎么让额外的应用端控制设备
- 应用可在不关闭控制通道的情况下切换权限
PENDING_ACK：重置等待 ack 超时时间

GVSP

A stream channel enables data transfer from a GVSP transmitter to a GVSP receiver. This transfer uses the GigE Vision Streaming Protocol (GVSP).
允许 1-512 个连接
也是基于 UDP IPv4， IP头也是固定20字节不使用IP头可选项
GVSP 的包大小不要求32位对齐，包大小取决于链路之间的MTU大小 -SCPSx 只决定数据负载（data payload）的包的大小, 数据头包（data leader）与尾包(data trailer)还是限定576字节大小的包。
标准传输模式（Standard Transmission mode），把数据分为 data leader, data payload, data trailer 三部分package
全入传输模式（All-in Transmission Mode），一个package全包含 data leader, payload, trailer. 可选，不一定支持