【SDK案例系列 01】基于MindX SDK的视频转码应用案例详解

源码链接：
https://gitee.com/ai_samples/atlas_mindxsdk_samples/tree/master/contrib/cv/data_process/video_transcoding

一、使用live555搭建 rtsp server

（1）安装live555

wget http://www.live555.com/liveMedia/public/live555-latest.tar.gz
tar xzf live555-latest.tar.gz
cd live
./genMakefiles linux-64bit #注意后面这个参数是根据当前文件夹下config.<后缀>获取得到的
make

（2）启动rtsp server

cd mediaServer
./live555MediaServer

（3）验证rtsp server是否正常

下面上传文件到 live555MediaServer 同级目录

[root@localhost mediaServer]#
[root@localhost mediaServer]# ls
COPYING         DynamicRTSPServer.cpp  DynamicRTSPServer.o  live555MediaServer.cpp  Makefile       Makefile.tail  video.264
COPYING.LESSER  DynamicRTSPServer.hh   live555MediaServer   live555MediaServer.o    Makefile.head  version.hh
[root@localhost mediaServer]# 

我上传了一个 video.264 那么，使用http协议访问的地址就行 http://你的ip:8000/文件名

例：http://127.0.0.1:8000/video.264；

使用rtsp协议访问的地址 http://你的ip/文件名

例：rtsp://127.0.0.1/video.264

然后请准备一个流媒体播放器，我下载的是vlc播放器

输入测试地址：

输入测试地址后点击播放，播放的时候能看到视频，说明rtsp server功能正常。

二、安装昇腾驱动

先安装昇腾驱动，昇腾驱动请参考各个产品安装手册，安装完成后npu-smi info 显示安装成功

[root@localhost ~]#
[root@localhost ~]# npu-smi info
+-------------------------------------------------------------------------------------------------+
| npu-smi 22.0.2                   Version: 22.0.2                                                |
+------------------+--------------+---------------------------------------------------------------+
| NPU    Name      | Health       | Power(W)             Temp(C)           Hugepages-Usage(page)  |
| Chip   Device    | Bus-Id       | AICore(%)            Memory-Usage(MB)                         |
+==================+==============+===============================================================+
| 1      310       | OK           | 12.8                 45                0   / 0                |
| 0      0         | 0000:05:00.0 | 0                    2621  / 8192                             |
+==================+==============+===============================================================+

三、安装MindX SDK > mxVision

（1）MindX SDK需要通过官网获取。

（2）mxVision说明手册：

https://www.hiascend.com/document/detail/zh/mind-sdk/30rc3/quickstart/visionquickstart/visionquickstart_0000.html

（3）安装MindX SDK

./Ascend-mindxsdk-mxvision_3.0.RC2_linux-aarch64.run --install --install-path=/usr/local/sdk_home

–install-path为指定安装的路径

（4）安装成功后会提示如下信息

Installing collected packages:mindx
Successfully installed mindx-3.0.RC2

（5）安装成功后在对应目录下查看，能看到mxVision

[root@localhost sdk_home]#
[root@localhost sdk_home]# pwd
/usr/local/sdk_home
[root@localhost sdk_home]# ls
mxVision mxVision-3.0.RC2
[root@localhost sdk_home]#
[root@localhost sdk_home]#

（6）MindX SDK使用中需要用到OSD功能，安装后需要执行以下命令，生成om文件

bash /usr/local/sdk_home/mxVision/operators/opencvosd/generate_osd_om.sh

执行成功后，显示如下效果

[root@localhost ~]# bash /usr/local/sdk_home/mxVision/operators/opencvosd/generate_osd_om.sh
ASCEND_HOME is set to /usr/local/Ascend by user
Set ASCEND_VERSION to the default value:ascend-toolkit/latest
ATC start working now,please wait for a moment.
ATC run success, welcome to the next use.

The model has been successfully converted to om,please get it under /usr/local/sdk_home/mxVision/operators/opencvosd.
[root@localhost ~]# 

（9）安装完MindX SDK后，需要配置环境变量

.bashrc文件添加以下环境变量

# 安装mxVision时配置
. /usr/local/sdk_home/mxVision/set_env.sh

用户也可以通过修改~/.bashrc文件方式设置永久环境变量，操作如下：

a) 以运行用户在任意目录下执行vi ~/.bashrc命令，打开.bashrc文件，在文件最后一行后面添加上述内容。

b) 执行:wq!命令保存文件并退出。

c) 执行source ~/.bashrc命令使其立即生效。

四、使用video_transcoding

1、修改run_cpp.sh中MX_SDK_HOME为MindX SDK安装目录

export MX_SDK_HOME=/usr/local/sdk_home/mxVision

2、修改data/pipeline/test.pipeline中rtspUrl，rtspUrl修改为拉取视频流的链接

"rtspUrl": "rtsp://127.0.0.1/video.264"

3、修改run_cpp.sh权限

chmod +x run_cpp.sh

4、执行run_cpp.sh

./run_cpp.sh

5、目录下会生成out.h264

[root@localhost video_transcoding]#
[root@localhost video_transcoding]# ls
README.md  build  cpp  data  main  out.h264  run_cpp.sh
[root@localhost video_transcoding]# 

五、video_transcoding详解

1、技术流程图

视频解码：调用硬件（DVPP）解码能力，转换为 YUV 格式图像数据。

图像缩放：基于硬件（DVPP）图像加速处理能力，将图像缩放到一定尺寸大小。

视频编码：调用硬件（DVPP）编码能力，将 YUV 格式的图像数据转换为 H264 视频流。

2、pipeline详解

{
    "encoder": {
        "stream_config": {  ##设置业务流在哪个芯片上处理
            "deviceId": "0"
        },
        "mxpi_rtspsrc0": {  ##拉取视频流
            "props": {
                "rtspUrl": "rtsp://127.0.0.1/video.264",
                "channelId": "0"
            },
            "factory": "mxpi_rtspsrc",
            "next": "queue0"
        },

        "queue0":{  ##队列缓存
            "props":{
                "max-size-buffers":"50"
            },
            "factory":"queue",
            "next": "mxpi_videodecoder0"
        },

        "mxpi_videodecoder0": {  ##视频解码（纯硬件）
            "props": {
                "inputVideoFormat": "H264",
                "outputImageFormat": "YUV420SP_NV12",
                "vdecChannelId": "0"
            },
            "factory": "mxpi_videodecoder",
            "next": "queue1"
        },

        "queue1":{  ##队列缓存
            "props":{
                "max-size-buffers":"50"
            },
            "factory":"queue",
            "next": "mxpi_imageresize0"
        },

        "mxpi_imageresize0": {  ##视频缩放（纯硬件）
            "props": {
                "dataSource": "mxpi_videodecoder0",
                "resizeHeight": "288",
                "resizeWidth": "352"
            },
            "factory": "mxpi_imageresize",
            "next": "queue2"
        },

        "queue2":{  ##队列缓存
            "props":{
                "max-size-buffers":"50"
            },
            "factory":"queue",
            "next": "mxpi_videoencoder0"
        },

        "mxpi_videoencoder0": {  ##视频编码（纯硬件）
            "props": {
                "dataSource": "mxpi_imageresize0",
                "imageHeight": "288",
                "imageWidth": "352",
                "inputFormat": "YUV420SP_NV12",
                "outputFormat": "H264",
                "fps": "1",
                "iFrameInterval": "50"
            },
            "factory": "mxpi_videoencoder",
            "next": "queue3"
        },

        "queue3":{  ##队列缓存
            "props":{
                "max-size-buffers":"50"
            },
            "factory":"queue",
            "next": "appsink0"
        },

        "appsink0": {  ##视频流输出
            "factory": "appsink"
        }
   }
}

3、源码详解

namespace {
    std::string ReadPipelineConfig(const std::string& pipelineConfigPath)  // 读取pipeline配置文件
    {
        std::ifstream file(pipelineConfigPath.c_str(), std::ifstream::binary);
        if (!file) {
            LogError << pipelineConfigPath <<" file dose not exist.";
            return "";
        }
        file.seekg(0, std::ifstream::end);
        uint32_t fileSize = file.tellg();
        file.seekg(0);
        std::unique_ptr<char[]> data(new char[fileSize]);
        file.read(data.get(), fileSize);
        file.close();
        std::string pipelineConfig(data.get(), fileSize);
        return pipelineConfig;
    }
}

int main(int argc, char* argv[])
{
    // 读取pipeline配置文件
    std::string pipelineConfigPath = "data/pipeline/test.pipeline";
    std::string pipelineConfig = ReadPipelineConfig(pipelineConfigPath);
    if (pipelineConfig == "") {
        LogError << "Read pipeline failed.";
        return APP_ERR_COMM_INIT_FAIL;
    }

    // 初始化 stream manager 资源
    MxStream::MxStreamManager mxStreamManager;
    APP_ERROR ret = mxStreamManager.InitManager();
    if (ret != APP_ERR_OK) {
        LogError << "Failed to init Stream manager, ret = " << ret << ".";
        return ret;
    }

    // 根据指定的pipeline配置创建Stream
    ret = mxStreamManager.CreateMultipleStreams(pipelineConfig);
    if (ret != APP_ERR_OK) {
        LogError << "Failed to create Stream, ret = " << ret << ".";
        return ret;
    }

    // 创建空的h264文件
    FILE *fp = fopen("./out.h264", "wb");
    if (fp == nullptr) {
        LogError << "Failed to open file.";
        return APP_ERR_COMM_OPEN_FAIL;
    }

    bool m_bFoundFirstIDR = false;
    bool bIsIDR = false;
    uint32_t frameCount = 0;
    uint32_t MaxframeCount = 1000;

    std::string streamName = "encoder";
    int inPluginId = 0;

    while (1) {
        // 获取视频编码后的视频帧
        MxStream::MxstDataOutput* output = mxStreamManager.GetResult(streamName, inPluginId);
        if (output == nullptr) {
            LogError << "Failed to get pipeline output.";
            return ret;
        }

        // H264视频格式，第一帧写入必须是IDR帧
        bIsIDR = (output->dataSize > 1);
        if(!m_bFoundFirstIDR)
        {
            if(!bIsIDR) {
                continue;
            } else {
                m_bFoundFirstIDR = true;
            }
        }

        // 把视频编码后的数据帧写入h264文件
        if (fwrite(output->dataPtr, output->dataSize, 1, fp) != 1) {
            LogInfo << "write frame to file fail";
        }

        frameCount++;
        if (frameCount > MaxframeCount) {
            LogInfo << "write frame to file done";
            break;
        }

        delete output;
    }

    // 关闭h264文件
    fclose(fp);

    // 销毁Streams
    mxStreamManager.DestroyAllStreams();

    return 0;
}