如何在视频中添加SRT文件中的字幕，并在c++程序中使用Gstreamer播放

Question

我想播放一个使用Gstreamer的C程序的视频，并从SRT文件中添加字幕。

我是gstreamer的新手，我不知怎么搞清楚了谁能让它在命令行中发挥作用：

gst-launch filesrc location=video.srt ! subparse ! \
    overlay. filesrc location=video.ogv ! oggdemux name=demux \
    demux. ! queue ! vorbisdec ! audioconvert ! autoaudiosink \
    demux. ! queue ! theoradec ! ffmpegcolorspace ! subtitleoverlay name=overlay ! autovideosink;

问题是，我可以播放一个C程序的视频，但我不知道如何添加字幕。

int main (int argc, char *argv[]) {
    GMainLoop *loop;

    GstElement *pipeline, *source, *demuxer, *audioDecoder, *videoDecoder, *audioConv, *videoConv, *videosink, 
            *audiosink, *audioQueue, *videoQueue;
    GstBus *bus;

    gst_init (&argc, &argv);

    loop = g_main_loop_new (NULL, FALSE);

    if (argc < 2 && argc > 3) {
        g_printerr ("Usage: %s <Ogg/Vorbis filename> [Srt filename]\n", argv[0]);
        return -1;
    }

    pipeline     = gst_pipeline_new ("audiovideo-player");
    source       = gst_element_factory_make ("filesrc",          "file-source");
    demuxer      = gst_element_factory_make ("oggdemux",         "ogg-demuxer");
    audioQueue   = gst_element_factory_make ("queue",            "audio-queue");
    videoQueue   = gst_element_factory_make ("queue",            "video-queue");
    audioDecoder = gst_element_factory_make ("vorbisdec",        "vorbis-decoder");
    videoDecoder = gst_element_factory_make ("theoradec",        "theora-decoder");
    audioConv    = gst_element_factory_make ("audioconvert",     "audio-converter");
    videoConv    = gst_element_factory_make ("ffmpegcolorspace", "video-converter");
    videosink    = gst_element_factory_make ("autovideosink",    "video-output");
    audiosink    = gst_element_factory_make ("autoaudiosink",    "audio-output");


    if (!pipeline || !source || !demuxer || !audioDecoder || !audioConv || !videoDecoder || !videoConv || !audioQueue 
            || !videoQueue || !audiosink || !videosink) {
        g_printerr ("One element could not be created. Exiting.\n");
        exit(-1);
    }

    g_object_set (G_OBJECT (source), "location", argv[1], NULL);

    bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
    gst_bus_add_watch (bus, bus_call, loop);
    gst_object_unref (bus);

    gst_bin_add_many (GST_BIN (pipeline),
                        source, demuxer, 
                        audioQueue, videoQueue, audioDecoder, videoDecoder,
                        videoConv, audioConv, videosink, audiosink, NULL);

    gst_element_link (source, demuxer);

    gst_element_link_many (videoQueue, videoDecoder, videoConv, videosink, NULL);
    g_signal_connect (demuxer, "pad-added", G_CALLBACK (on_pad_added), videoQueue);

    gst_element_link_many (audioQueue, audioDecoder, audioConv, audiosink, NULL);
    g_signal_connect (demuxer, "pad-added", G_CALLBACK (on_pad_added), audioQueue);

    g_print ("Lecture de : %s\n", argv[1]);
    gst_element_set_state (pipeline, GST_STATE_PLAYING);

    g_print ("En cours...\n");
    g_main_loop_run (loop);

    g_print ("Arret de la lecture\n");
    gst_element_set_state (pipeline, GST_STATE_NULL);
    g_print ("Suppression du pipeline\n");
    gst_object_unref (GST_OBJECT (pipeline));
    return 0;
} 

Answer 1

在pad添加的回调(您只需要连接一次！)你必须检查新增加的垫盖。

无论如何，文件中的视频还需要连接到子标题覆盖，您将链接视频接收器后，子标题覆盖。您还可以将字幕文件的附加文件to链接到子标题覆盖。

查看一下用于字幕处理的playbin /play接收器中的代码，特别是动态处理这些内容的代码。还要注意，playbin有一个sub属性，它允许您选择一个应该覆盖在视频上的外部字幕文件。

Answer 2

非常感谢塞巴斯蒂安博士，我终于可以播放这段带字幕的视频了。这是我做的代码。

gst_element_link_many (videoQueue, videoDecoder, videoConv, subOverlay, videosink, NULL);
g_signal_connect (demuxer, "pad-added", G_CALLBACK (on_pad_added), videoQueue);

gst_element_link_many (audioQueue, audioDecoder, audioConv, audiosink, NULL);
g_signal_connect (demuxer, "pad-added", G_CALLBACK (on_pad_added), audioQueue);


g_object_set (G_OBJECT (subSource), "location", argv[2], NULL);

现在我正在考虑使用GTK来添加一些功能，比如暂停视频，它可能需要清理一点，但现在还可以。