ubuntu GStreamer + QT多媒体播放器开发（三）

本篇博客在上一篇ubuntu GStreamer + QT多媒体播放器开发（二）的基础上主要修改新增以下几点：
（1）log 分为trace、info、debug、warn、error五个级别打印;
（2）mmplayer lib新增MMPlayerPause 接口。
（3）QT(UI)层更改为通过control thread 控制播放、暂停、停止等功能，通过command queue实现异步响应UI 点击事件;
（4）QT 窗口退出时增加资源释放的流程。
（5）优化QT project cmake file.
以下对新增的部分简单进行说明。

1 log分级打印

项目开发过程中，日志系统必不可少。对于c语言项目，平常的练习和简单的开发过程中可以直接用 printf 打印程一些调试信息，但是对于大一点的项目，必须分级打印，这样在开发阶段可以把所以log信息打出来，方便调试，而项目正式上线以后只保留一些关键log，提高程序运行效率，log分级打印要点实现过程如下：
（1）定义log打印级别枚举：

/*log level*/
typedef enum {LOG_LEVEL_OFF,LOG_LEVEL_ERROR,LOG_LEVEL_WARN,LOG_LEVEL_INFO,LOG_LEVEL_DEBUG,LOG_LEVEL_TRACE,LOG_LEVEL_ALL,
} LOG_LEVEL;

（2）宏定义不同等级的log打印函数，根据设置的log_level来判断是否打印该级别的log，打印log的宏函数可以通过printf或g_print（glib 提供的打印函数）实现。

#define LIB_NAME "mmplayer"static LOG_LEVEL log_level;#define LOG_ENTER()  \
do {                            \if (log_level >= LOG_LEVEL_TRACE) {    \g_print("[%s][IN][%s][%d]\n", LIB_NAME, __FUNCTION__, __LINE__); \}  \
} while(0)#define LOG_OUT() \
do {                            \if (log_level >= LOG_LEVEL_TRACE) {    \g_print("[%s][OUT][%s][%d]\n", LIB_NAME, __FUNCTION__, __LINE__);    \}  \
} while(0)#define LOG_DEBUG(format,...) \
do {                            \if (log_level >= LOG_LEVEL_DEBUG) {    \g_print("[%s][DEBUG][%s][%d]"format"", LIB_NAME, __FUNCTION__, __LINE__, ##__VA_ARGS__);   \}  \
} while(0)#define LOG_INFO(format,...)  \
do {                            \if (log_level >= LOG_LEVEL_INFO) { \g_print("[%s][INFO][%s][%d]"format"", LIB_NAME, __FUNCTION__, __LINE__, ##__VA_ARGS__);    \}  \
} while(0)#define LOG_WARN(format,...)  \
do {                            \if (log_level >= LOG_LEVEL_WARN) { \g_print("[%s][WARN][%s][%d]"format"", LIB_NAME, __FUNCTION__, __LINE__, ##__VA_ARGS__);    \}  \
} while(0)#define LOG_ERROR(format,...) \
do {                            \if (log_level >= LOG_LEVEL_ERROR) {    \g_print("[%s][ERROR][%s][%d]"format"", LIB_NAME, __FUNCTION__, __LINE__, ##__VA_ARGS__);   \}  \
} while(0)

（3）初始化的时候设置log级别：

log_level = pstInitParam->logLevel;

印出的log 如下：

[userplayer][INFO][main][38]malloc MEM(0x558bd56563b0)
[mmplayer][OUT][MMPlayerInit][119]
[mmplayer][INFO][handle_element_added][334]elementName uridecodebin3-0.
[mmplayer][INFO][handle_element_added][334]elementName urisourcebin0.
[mmplayer][INFO][handle_element_added][334]elementName source.
[mmplayer][INFO][handle_element_added][334]elementName typefindelement0.
[userplayer][INFO][hanleCallBackEvent][114]recive event type (0)
[userplayer][INFO][hanleCallBackEvent][119]player init OK!
[userplayer][INFO][main][63]recive palyer init OK msg
[userplayer][INFO][_palyer_control_thread][151]control thread enter

2 mmplayer lib新增MMPlayerPause 接口

MMPlayerPause实现暂停播放的功能，主要把pipeline状态设置为GST_STATE_PAUSED，内容比较简单。

int MMPlayerPause(HANDLE_ID hanldeId)
{GstStateChangeReturn stateRet;int ret = 0;LOG_ENTER();if (!mediaHandle || !mediaHandle->pipeline){LOG_ERROR ("handle or pipeline is NULL.\n");ret = -1;goto end;}stateRet = gst_element_set_state (mediaHandle->pipeline, GST_STATE_PAUSED);if (stateRet == GST_STATE_CHANGE_FAILURE) {LOG_ERROR ("Unable to set the pipeline to the pause state.\n");ret = -1;goto end;}LOG_OUT();
end:if (ret != 0){g_main_loop_quit (mediaHandle->main_loop);}return ret;
}

3 UI层通过control thread 控制播放、暂停、停止等功能

设计思路：创建一个command queue，点击UI上的按钮时将对应type的cmd和一些data push到queue中，QT中创建一个control thread ,取出cmd queue中的cmd ,根据cmd type 调用mmplayer lib中接口实现播放控制，这样可以实现异步响应UI 操作，可以提升一些耗时比较长场景的用户体验。
cmd type 枚举定义：

typedef enum {CMD_PLAY,CMD_PAUSE,CMD_RESUME,CMD_STOP,CMD_SEEK,CMD_ALL,
} MM_PLAYER_CMD_TYPE;

cmd queue数据结构的定义：

#define MAX_QUEUE_ESIZE 4
typedef struct _ST_PLAYER_CMD
{MM_PLAYER_CMD_TYPE type;int seekTime;int volumeValue;
} ST_PLAYER_CMD;typedef struct _ST_PLAYER_CMD_QUEUE
{ST_PLAYER_CMD *cmd[MAX_QUEUE_ESIZE];int front;int rear;int length;
} ST_PLAYER_CMD_QUEUE;

cmd queue中存放的是ST_PLAYER_CMD 结构体，该结构体存放的是cmd type和一下user data，如做seek时需要设置seek time等，后期需要其他数据再扩充。
接下来定义操作cmd queue的函数，主要涉及queue 初始化、是否为空、是否已满、push cmd 到queue、从queue 中pop一个cmd、销毁queue，详细的原理可以参考queue数据结构。

bool cmdQueueInit(ST_PLAYER_CMD_QUEUE **cmdQueue);
bool cmdQueueIsEmpty(ST_PLAYER_CMD_QUEUE *cmdQueue);
bool cmdQueueIsFull(ST_PLAYER_CMD_QUEUE *cmdQueue);
bool cmdQueuePush(ST_PLAYER_CMD_QUEUE *cmdQueue);
ST_PLAYER_CMD *cmdQueuePop(ST_PLAYER_CMD_QUEUE *cmdQueue);
bool cmdQueueDeInit(ST_PLAYER_CMD_QUEUE *cmdQueue);
bool createCmdAndPush(ST_USER_HANDLE *userHandle, MM_PLAYER_CMD_TYPE type, void *data);

初始化queque，注意传入的参数是cmd queue指针的指针:

bool cmdQueueInit(ST_PLAYER_CMD_QUEUE **cmdQueue)
{bool ret = false;ST_PLAYER_CMD_QUEUE *retQueue = NULL;if (NULL == cmdQueue){LOG_ERROR("cmd queue is NULL\n");goto end;}retQueue = (ST_PLAYER_CMD_QUEUE *)g_malloc(sizeof(ST_PLAYER_CMD_QUEUE));if (retQueue == NULL){LOG_ERROR("malloc cmd queue error\n");goto end;}memset(retQueue->cmd, 0, sizeof(retQueue->cmd));retQueue->rear = retQueue->front = 0;retQueue->length = 0;*cmdQueue = retQueue;ret = true;
end:return ret;
}

判断queue是否为空：

bool cmdQueueIsEmpty(ST_PLAYER_CMD_QUEUE *cmdQueue)
{bool ret = false;if (NULL == cmdQueue){LOG_ERROR("cmd queue is NULL\n");goto end;}ret = (cmdQueue->rear == cmdQueue->front ? true : false);end:return ret;
}

判断queue是否已满：

bool cmdQueueIsFull(ST_PLAYER_CMD_QUEUE *cmdQueue)
{bool ret = false;if (NULL == cmdQueue){LOG_ERROR("cmd queue is NULL\n");goto end;}ret = ((cmdQueue->rear + 1) % MAX_QUEUE_ESIZE == cmdQueue->front ? true : false);end:return ret;
}

向queue中push 一个cmd:

bool cmdQueuePush(ST_PLAYER_CMD_QUEUE *cmdQueue, ST_PLAYER_CMD *cmd)
{bool ret = false;if (NULL == cmdQueue || NULL == cmd){LOG_ERROR("cmd queue is NULL\n");goto end;}if (cmdQueueIsFull(cmdQueue)){LOG_ERROR("cmd queue is full, throw cmd (%d)\n", cmd->type);goto end;}cmdQueue->cmd[cmdQueue->rear] = cmd;cmdQueue->rear = (cmdQueue->rear + 1) % MAX_QUEUE_ESIZE;ret = true;LOG_INFO ("push cmd(%d) to queue success\n", cmd->type);end:return ret;
}

从queue中取出一个cmd:

ST_PLAYER_CMD *cmdQueuePop(ST_PLAYER_CMD_QUEUE *cmdQueue)
{ST_PLAYER_CMD *ret = NULL;if (NULL == cmdQueue){LOG_ERROR("cmd queue is NULL\n");goto end;}if (cmdQueue->rear == cmdQueue->front){LOG_ERROR("cmd queue is empty\n");goto end;}ret = cmdQueue->cmd[cmdQueue->front];cmdQueue->cmd[cmdQueue->front] = NULL;cmdQueue->front = (cmdQueue->front + 1) % MAX_QUEUE_ESIZE;end:return ret;
}

销毁queue:

bool cmdQueueDeInit(ST_PLAYER_CMD_QUEUE *cmdQueue)
{bool ret = false;int i = 0;if (NULL == cmdQueue){LOG_ERROR("cmd queue is NULL\n");goto end;}LOG_INFO("start free cmd\n");for (i = 0; i < MAX_QUEUE_ESIZE; i++){if (cmdQueue->cmd[i]){LOG_INFO ("free cmd(%p)\n", cmdQueue->cmd[i]);g_free(cmdQueue->cmd[i]);cmdQueue->cmd[i] = NULL;}}cmdQueue->rear = cmdQueue->front = 0;cmdQueue->length = 0;ret = true;
end:return ret;
}

UI 向cmd queue中写cmd时不直接调用cmdQueuePop函数，而是基于该函数封装一个createCmdAndPush函数，这样为了扩充后期复杂的cmd，如seek、倍速播放。

bool createCmdAndPush(ST_USER_HANDLE *userHandle, MM_PLAYER_CMD_TYPE type, void *data)
{bool ret = false;ST_PLAYER_CMD *cmd = NULL;if (NULL == userHandle || type > CMD_ALL){LOG_ERROR("invalid param\n");goto end;}cmd = (ST_PLAYER_CMD *)g_malloc(sizeof(ST_PLAYER_CMD));if (cmd == NULL){LOG_ERROR("malloc cmd error\n");goto end;}cmd->type = type;switch (type){case CMD_PLAY:{break;}case CMD_PAUSE:{break;}case CMD_RESUME:{break;}case CMD_STOP:{break;}case CMD_SEEK:{break;}default:{break;}}g_mutex_lock(&userHandle->queueMutex);ret = cmdQueuePush(userHandle->cmdQueue, cmd);g_cond_signal(&userHandle->queueCond);g_mutex_unlock(&userHandle->queueMutex);end:if (ret == false && cmd != NULL){//need free cmd when errorg_free(cmd);cmd = NULL;ret = false;}return ret;
}

需要注意的是createCmdAndPush函数中向queue中写cmd时必须使用mutex，再配合信号量使用。
UI按钮点击时要push cmd到queue中调用createCmdAndPush函数即可。

void PlayerWindow::onPlayClicked() {bool ret = false;MM_PLAYER_CMD_TYPE type = CMD_PLAY;if (NULL == pstHandle){LOG_ERROR("pst is NULL\n");goto end;}ret = createCmdAndPush(pstHandle, type, NULL);if (!ret){LOG_ERROR("start play error\n");}end:LOG_OUT();
}

以上过程实现cmd 的push，main函数中需要初始化queue以及cmd queue使用的mutex和cond，并创建control thread取出queue中的cmd:

    //init cmd queueg_mutex_init(&userHandle->queueMutex);g_cond_init(&userHandle->queueCond);cmdQueueInit(&userHandle->cmdQueue);userHandle->controlThread = g_thread_new("control_thread", _palyer_control_thread, userHandle);if (!userHandle->controlThread){LOG_ERROR ("create control thread fail.\n");}

_palyer_control_thread的内容如下，取出cmd queue并调用mmplayer lib中的接口，这样一个异步操作就实现了，最后thread 退出时记得销毁cmd queue和queue使用的mutex 和cond。

void *_palyer_control_thread(void* Parameter)
{ST_USER_HANDLE *pstUserHandle = (ST_USER_HANDLE *)Parameter;ST_PLAYER_CMD *curCmd = NULL;if (NULL == pstUserHandle){LOG_ERROR ("handle is NULL.\n");}LOG_INFO("control thread enter\n");while(pstUserHandle->handleStatus < ERROR_STATUS){while (!cmdQueueIsEmpty(pstUserHandle->cmdQueue)){LOG_INFO("queue not empty\n");g_mutex_lock(&pstUserHandle->queueMutex);curCmd = cmdQueuePop(pstUserHandle->cmdQueue);g_mutex_unlock(&pstUserHandle->queueMutex);if (curCmd == NULL){LOG_INFO("cmd is empty\n");break;}switch (curCmd->type){case CMD_PLAY:{MMPlayerPlay(pstUserHandle->handleId);break;}case CMD_PAUSE:{MMPlayerPause(pstUserHandle->handleId);break;}case CMD_RESUME:{break;}case CMD_STOP:{MMPlayerStop(pstUserHandle->handleId);break;}case CMD_SEEK:{break;}default:break;}//need free cmd hereif (curCmd){g_free(curCmd);}}if (cmdQueueIsEmpty(pstUserHandle->cmdQueue)){//wait new cmd push in cmd queueLOG_INFO("start wait new cmd...\n");g_mutex_lock(&pstUserHandle->queueMutex);g_cond_wait(&pstUserHandle->queueCond, &pstUserHandle->queueMutex);g_mutex_unlock(&pstUserHandle->queueMutex);LOG_INFO("wait new cmd done\n");}}LOG_INFO("quit control thread\n");cmdQueueDeInit(pstUserHandle->cmdQueue);//control thead stop free cmd queueif (pstUserHandle->cmdQueue){g_free(pstUserHandle->cmdQueue);pstUserHandle->cmdQueue = NULL;}g_mutex_clear(&pstUserHandle->queueMutex);g_cond_clear(&pstUserHandle->queueCond);g_thread_unref(pstUserHandle->controlThread);pstUserHandle->controlThread = NULL;//emit quit signalg_mutex_lock(&userHandle->quitMutex);g_cond_signal(&userHandle->quitCond);g_mutex_unlock(&userHandle->quitMutex);}

4 QT 窗口退出时增加资源释放的流程

程序中创建了一个player thread ,一个control thread以及一些handle 资源，点击QT 窗口退出时必须保证两个thread都退出，申请的资源都free调，否则会造成内存泄漏。资源释放流程设计如下
（1）关闭窗口时会触发closeEvent，在closeEvent 中push 一个stop cmd ：

void PlayerWindow::closeEvent(QCloseEvent *event)
{bool ret = false;MM_PLAYER_CMD_TYPE type = CMD_STOP;if (NULL == pstHandle){LOG_ERROR("pst is NULL\n");goto end;}ret = createCmdAndPush(pstHandle, type, NULL);...
}

（2）control thread 中取出stop cmd后调用MMPlayerStop函数，MMPlayerStop函数调用后退出main loop，退出paly thread ,释放mmplayer lib中的相关资源，释放完毕后向UI层返回PLAYER_STOP_OK event

    mediaHandle->handleInfo.handleStatus = STOP_STATUS;if (mediaHandle->hanlecallBackFn){(mediaHandle->hanlecallBackFn)(PLAYER_STOP_OK ,(void *)&mediaHandle->handleInfo);}

（3）UI收到PLAYER_STOP_OK event后将handleStatus 设置为ERROR_STATUS，并调用g_cond_signal，让control thread 退出。

        case PLAYER_STOP_OK:{LOG_INFO("pipeline deinit OK! \n");userHandle->handleStatus = ERROR_STATUS;g_mutex_lock(&userHandle->queueMutex);g_cond_signal(&userHandle->queueCond);g_mutex_unlock(&userHandle->queueMutex);break;}

（4）为了让closeEvent等待所有资源释放完毕，使用了条件变量，closeEvent中发送完stop cmd 后开始等待条件变量，control thread 退出后发送信号量，让closeEvent结束等待。
closeEvent：

    ret = createCmdAndPush(pstHandle, type, NULL);if (!ret){LOG_ERROR("start play error\n");}g_mutex_lock(&pstHandle->quitMutex);g_cond_wait(&pstHandle->quitCond, &pstHandle->quitMutex);g_mutex_unlock(&pstHandle->quitMutex);

control thread：

    //emit quit signalg_mutex_lock(&userHandle->quitMutex);g_cond_signal(&userHandle->quitCond);g_mutex_unlock(&userHandle->quitMutex);

这样就可以安全释放所用申请的资料了。

5 优化QT project cmake file

项目编译的时候先进player_lib中执行make 编译mmplayer lib，编译后会自动把lib的so和头文件copy到QT project 目录。QT project 使用了cmake编译，cmake文件如下：

cmake_minimum_required(VERSION 3.5)
project(gst_player LANGUAGES CXX C)set(CMAKE_INCLUDE_CURRENT_DIR ON)set(CMAKE_AUTOUIC ON)
set(CMAKE_AUTOMOC ON)
set(CMAKE_PROJECT_NAME gst_player)set(CMAKE_CXX_STANDARD 11)
set(CMAKE_CXX_STANDARD_REQUIRED ON)find_package(PkgConfig REQUIRED)
pkg_check_modules(gstreamer REQUIRED IMPORTED_TARGET gstreamer-1.0)
pkg_check_modules(gstreamer-video REQUIRED IMPORTED_TARGET gstreamer-video-1.0)
pkg_check_modules(gobject REQUIRED IMPORTED_TARGET gobject-2.0)
pkg_check_modules(glib REQUIRED IMPORTED_TARGET glib-2.0)# shell中编译打开以下注释，Qt5_DIR设置为QT安装路径
#set(Qt5_DIR "/home/zhy/Qt5.13.2/5.13.2/gcc_64/lib/cmake/Qt5")
#find_package (Qt5Widgets)
#find_package (Qt5Core)
#find_package (Qt5Gui)# qt create中编译，shell下编译需注释
find_package(Qt5 REQUIRED COMPONENTS Widgets )include_directories(${PROJECT_SOURCE_DIR}/common/)
include_directories(${PROJECT_SOURCE_DIR}/libs/)
link_directories(${PROJECT_SOURCE_DIR}/libs/)
find_library (libpath mmplayer ${PROJECT_SOURCE_DIR}/libs/)if (${libpath} STREQUAL "libpath-NOTFOUND")message (STATUS "required mmplayer library but not found!")
else()message (STATUS "libpath library found in ${libpath}")
endif()add_executable(gst_playermain.cppplayerwindow.cppplayerwindow.hcommon/common.hcommon/common.cpplibs/mediaPlayer.h
)target_link_libraries(gst_player PRIVATE Qt5::Widgets PkgConfig::gstreamer PkgConfig::gstreamer-video PkgConfig::gobject PkgConfig::glib mmplayer)

项目github地址：https://github.com/zhenghaiyang123/gst_player.git，本篇博客对应的tag为v0.3。