【QGroundControl二次开发】十. QT添加GStreamer视频播放同时保存

上一章介绍使用QT播放GStreamer视频流【QGroundControl二次开发】八. QT实现播放gstreamer视频。
这章介绍如何在原有基础上保存为视频，同时保存为一个个规定大小的小视频。

一. 思想

之前的文章展示了如何在QT中播放GST视频流，这章在原有的基础上增加了一部分代码。原理就是使用Gstreamer的tee为管道开一条支流。大致图示如下（增加一条保存分路）：
在这里插入图片描述

二. 增加代码

2.1 创建文件分路所需元素

record_queue = gst_element_factory_make("queue", "record_queue");
video_rate = gst_element_factory_make("videorate", "video_rate");
jpeg_enc = gst_element_factory_make("jpegenc", "jpeg_enc");
avi_mux = gst_element_factory_make("avimux", "avi_mux");
file_sink = gst_element_factory_make ("filesink", "file_sink");

2.2 把这些保存视频要使用的元素放进管道。

gst_bin_add_many(GST_BIN (pipeline), record_queue,video_rate,jpeg_enc,avi_mux,file_sink, NULL);
gst_element_sync_state_with_parent(record_queue);

// link element
if(gst_element_link_many(record_queue,video_rate,jpeg_enc,avi_mux,file_sink, NULL) != TRUE){
    g_printerr ("Elements could not be linked.\n");
    gst_object_unref (pipeline);
    return -1;
}
g_object_set (G_OBJECT(file_sink),"location",videofilename,NULL);

2.3 把支路和主路连接起来。

//Manually link the Tee, which has "Request" pads
tee_record_pad = gst_element_get_request_pad (tee, "src_%u");
g_print ("Obtained request pad %s for record branch.\n", gst_pad_get_name (tee_record_pad));
queue_record_pad = gst_element_get_static_pad (record_queue, "sink");
if (!queue_record_pad) g_printerr ("queue_record_pad not be get.\n");
// 链接tee的MP4分支到mp4mux
if (gst_pad_link(tee_record_pad, queue_record_pad) != GST_PAD_LINK_OK) {
    g_printerr("Tee MP4 branch could not be linked.\n");
    gst_object_unref(pipeline);
    return -1;
}

//设置队列参数
g_object_set (G_OBJECT(record_queue),"max-size-buffers",0,NULL);
g_object_set (G_OBJECT(record_queue),"max-size-time",0,NULL);
g_object_set (G_OBJECT(record_queue),"max-size-bytes",512000000,NULL);
//释放pad
gst_object_unref (queue_record_pad);

最后保存的为MP4文件，尝试x264enc,mp4mux 无发连接管道，但是使用jpeg_enc,avi_mux可以保存和播放MP4视频。。。

三. 改进

由于一直保存视频会导致文件特别大，需要将保存的视频按需自动分成一个一个的规定大小或时间的视频，就要用到splitmuxsink 元素。

splitmuxsink 是 GStreamer 中一个非常有用的元素，它可以在达到最大文件大小或时间阈值时，自动分割视频文件，且分割操作在视频关键帧边界进行，保证了视频片段的完整性。通俗讲splitmuxsink = muxer + sink。

默认情况下，splitmuxsink 使用 mp4mux 作为muxer和 filesink 作为sink，但也可以通过设置相应的属性来使用其他的muxer和sink。

//文件分路所需元素
record_queue = gst_element_factory_make("queue", "record_queue");
video_rate = gst_element_factory_make("videorate", "video_rate");
jpeg_enc = gst_element_factory_make("jpegenc", "jpeg_enc");
avi_mux = gst_element_factory_make("avimux", "avi_mux");
splitmuxsink= gst_element_factory_make("splitmuxsink", "splitmuxsink");
file_sink = gst_element_factory_make ("filesink", "file_sink");

g_object_set(G_OBJECT(splitmuxsink),
             "muxer", avi_mux,
             "sink", file_sink,
             "max-size-time", (guint64)90*GST_SECOND,
             "max-files", 20,
             "location",filename , NULL);

这段代码设置splitmuxsink参数,每段视频最长90秒,每次最多保存20个视频文件超出覆盖最旧的文件。max-size-time 和 max-size-bytes 属性分别用来设置文件的最大时间和大小限制。max-files 属性允许你指定要保留在磁盘上的最大文件数。当达到此最大值时，最旧的文件将开始被删除以为新文件腾出空间。

四. 效果

在这里插入图片描述

五. 完整代码:

#include <QApplication>
#include <QWidget>
#include <QtConcurrent/QtConcurrent>
#include <gst/gst.h>
#include <glib.h>
#include <gst/video/videooverlay.h>
#include "ui_mainwindow.h"


int main(int argc, char *argv[]) {
    // 获取当前时间
    QString filename = "video%02d.mp4";
    //初始化程序
    QApplication a(argc, argv);

    GstElement *pipeline, *udpsrc, *capsfilter, *disp_queue, *rtph264depay, *h264parse, *avdec_h264, *videoconvert, *vsink;
    GstCaps *caps;
    // 创建新元素
    GstElement *tee, *record_queue,*video_rate, *avi_mux, *jpeg_enc, *file_sink,*splitmuxsink;
    GstPad *tee_record_pad, *queue_record_pad;

    GstStateChangeReturn ret;

    QWidget *window = new QWidget();
    window->resize(1920, 1080);
    window->show();
    WId xwinid = window->winId();

    // 初始化 GStreamer
    gst_init(NULL, NULL);

    // 创建元素
    pipeline = gst_pipeline_new("my-pipeline");
    udpsrc = gst_element_factory_make("udpsrc", "udpsrc");
    capsfilter = gst_element_factory_make("capsfilter", "capsfilter");
    disp_queue = gst_element_factory_make("queue", "disp_queue");
    tee = gst_element_factory_make ("tee", "tee");
    h264parse = gst_element_factory_make("h264parse", "h264parse");
    avdec_h264 = gst_element_factory_make("avdec_h264", "avdec_h264");
    rtph264depay = gst_element_factory_make("rtph264depay", "rtph264depay");
    videoconvert = gst_element_factory_make("videoconvert", "videoconvert");
    vsink = gst_element_factory_make("xvimagesink", "vsink");//glimagesink
    //文件分路所需元素
    record_queue = gst_element_factory_make("queue", "record_queue");
    video_rate = gst_element_factory_make("videorate", "video_rate");
    jpeg_enc = gst_element_factory_make("jpegenc", "jpeg_enc");
    avi_mux = gst_element_factory_make("avimux", "avi_mux");
    splitmuxsink= gst_element_factory_make("splitmuxsink", "splitmuxsink");
    file_sink = gst_element_factory_make ("filesink", "file_sink");

    //设置splitmuxsink参数,每段视频最长90秒,每次最多保存20个视频文件超出覆盖最旧的文件
    g_object_set(G_OBJECT(splitmuxsink),
                 "muxer", avi_mux,
                 "sink", file_sink,
                 "max-size-time", (guint64)90*GST_SECOND,
                 "max-files", 20,
                 "location",filename , NULL);
    // 设置 udpsrc 元素的参数
    g_object_set(udpsrc, "port", 25600, NULL);
    // 创建 caps
    caps = gst_caps_new_simple("application/x-rtp",
                               "media", G_TYPE_STRING, "video",
                               "clock-rate", G_TYPE_INT, 90000,
                               "encoding-name", G_TYPE_STRING, "H264",
                               /*"depth", G_TYPE_STRING, "8",
                                * "width", G_TYPE_STRING, "1920",
                                * "height", G_TYPE_STRING, "1080",*/
                               NULL);
    g_object_set(capsfilter, "caps", caps, NULL);
    gst_caps_unref(caps);

    //检查元素
    if (!pipeline || !udpsrc || !capsfilter || !disp_queue || !rtph264depay || !h264parse || !avdec_h264 || !videoconvert || !file_sink || !vsink)
    {
        g_printerr("Failed to create elements. Exiting.\n0000000");
        return -1;
    }

    // 将元素添加到管道中
    gst_bin_add_many(GST_BIN(pipeline), udpsrc, capsfilter, disp_queue, rtph264depay, h264parse, avdec_h264, videoconvert, vsink,tee,/*queue2, x264enc,mp4mux,file_sink,*/ NULL);
    if (gst_element_link_many (udpsrc,capsfilter,rtph264depay,h264parse, avdec_h264,videoconvert,tee,disp_queue, vsink, NULL) != TRUE /*||
                                                                    gst_element_link_many (queue2, x264enc,mp4mux,file_sink, NULL) != TRUE */)
    {

        g_printerr ("main Elements could not be linked.\n1111111111111111");
        gst_object_unref (pipeline);
        return -1;
    }

    //录像支路
    gst_bin_add_many(GST_BIN (pipeline), record_queue,video_rate,jpeg_enc,splitmuxsink, NULL);
    gst_element_sync_state_with_parent(record_queue);
    // link element
    if(gst_element_link_many(record_queue,video_rate,jpeg_enc,splitmuxsink, NULL) != TRUE){
        g_printerr ("Elements could not be linked.\n");
        gst_object_unref (pipeline);
        return -1;
    }

    //    g_object_set (G_OBJECT(file_sink),"location",videofilename,NULL);

    //Manually link the Tee, which has "Request" pads
    tee_record_pad = gst_element_get_request_pad (tee, "src_%u");
    g_print ("Obtained request pad %s for record branch.\n", gst_pad_get_name (tee_record_pad));
    queue_record_pad = gst_element_get_static_pad (record_queue, "sink");
    if (!queue_record_pad) g_printerr ("queue_record_pad not be get.\n");
    // 链接tee的MP4分支到mp4mux
    if (gst_pad_link(tee_record_pad, queue_record_pad) != GST_PAD_LINK_OK) {
        g_printerr("Tee MP4 branch could not be linked.\n");
        gst_object_unref(pipeline);
        return -1;
    }

    //设置队列参数
    g_object_set (G_OBJECT(record_queue),"max-size-buffers",0,NULL);
    g_object_set (G_OBJECT(record_queue),"max-size-time",0,NULL);
    g_object_set (G_OBJECT(record_queue),"max-size-bytes",512000000,NULL);
    //释放pad
    gst_object_unref (queue_record_pad);

    // 链接QT界面
    gst_video_overlay_set_window_handle (GST_VIDEO_OVERLAY (vsink), xwinid);

    // 设置管道状态为播放
    ret = gst_element_set_state(pipeline, GST_STATE_PLAYING);
    if (ret == GST_STATE_CHANGE_FAILURE) {
        g_printerr("Failed to set pipeline state to PLAYING. Exiting.\n");
        gst_object_unref(pipeline);
        return -1;
    }


    auto res = a.exec();

    // 释放资源
    g_free(videofilename);
    gst_element_set_state(pipeline, GST_STATE_NULL);
    gst_object_unref(pipeline);

    return res;
}