[参考译文] AM62A7：Gstreamer 错误&quot；vdec 3021100.video-codec：同步实例太多：32 (最大值：32)&quot；

尊敬的 Christoph：

您可以尝试通过以下方式动态修改流水线(而不实际将其暂停)：向流水线中的队列元素添加焊盘探头、并在焊盘探头回调中修改下游元素。 这可以使流水线保持正常运行、如果未使用该路径、则可以将下游元素替换为 fakesink。

演示机制的测试程序(videotestsrc -> tee -> 3个路径、使用控制台上的命令打开不同路径上的处理/显示)

#include <gst/gst.h>
#include <stdbool.h>
#include <glib.h>
#include <glib/gprintf.h>
#include <gio/gio.h>
#include <stdbool.h>

static GstPad *blockpad1, *blockpad2, *blockpad3;
static GstElement *pipeline;
static GstElement *q_stream1, *q_stream2, *q_stream3;
GQueue sink[3] = { G_QUEUE_INIT, G_QUEUE_INIT, G_QUEUE_INIT };

static GstPadProbeReturn pad_probe_cb(GstPad *pad, GstPadProbeInfo *info, gpointer user_data)
{
        GstPad *srcpad, *sinkpad;
        GstElement * parent = gst_pad_get_parent_element(pad), *element;
        char name[11];
        int stream = -1;
        gboolean fake = false;

        GST_DEBUG_OBJECT(pad, "pad is blocked now");

        if (g_ascii_strncasecmp(gst_object_get_name(GST_OBJECT(parent)), "queue-stream-1", 14) == 0) {
                stream = 0;
        }
        if (g_ascii_strncasecmp(gst_object_get_name(GST_OBJECT(parent)), "queue-stream-2", 14) == 0) {
                stream = 1;
        }
        if (g_ascii_strncasecmp(gst_object_get_name(GST_OBJECT(parent)), "queue-stream-3", 14) == 0) {
                stream = 2;
        }

        if (g_ascii_strncasecmp(gst_object_get_name(GST_OBJECT(g_queue_peek_head(&sink[stream]))), "fakesink", 8) == 0) {
                fake = true;
        }


        /* empty the queue of elements currently connected */
        while (!g_queue_is_empty(&sink[stream])) {
                element = g_queue_pop_head(&sink[stream]);
                gst_element_set_state(element, GST_STATE_NULL);

                GST_DEBUG_OBJECT(pipeline, "removing %" GST_PTR_FORMAT, element);
                gst_bin_remove(GST_BIN(pipeline), element);
        }

        if (fake) {
                GstElement *overlay, *new_sink;
                char text[9];
                sprintf(name, "overlay%d", stream + 1);
                overlay = gst_element_factory_make("textoverlay", name);
                g_object_set(overlay, "halignment", 0, NULL);
                sprintf(text, "Camera %d", stream + 1);
                g_object_set(overlay, "text", text, NULL);

                sprintf(name, "videosink%d", stream + 1);
                new_sink = gst_element_factory_make("xvimagesink", name);

                GST_DEBUG_OBJECT(pipeline, "adding %" GST_PTR_FORMAT "%" GST_PTR_FORMAT, overlay, new_sink);
                gst_bin_add_many(GST_BIN(pipeline), overlay, new_sink, NULL);

                GST_DEBUG_OBJECT(pipeline, "linking...");
                gst_element_link_many(parent, overlay, new_sink, NULL);

                gst_element_set_state(overlay, GST_STATE_PLAYING);
                gst_element_set_state(new_sink, GST_STATE_PLAYING);
                g_queue_push_tail(&sink[stream], overlay);
                g_queue_push_tail(&sink[stream], new_sink);
        } else {
                GstElement *new_sink;
                sprintf(name, "fakesink%d", stream + 1);
                new_sink = gst_element_factory_make("fakesink", name);

                GST_DEBUG_OBJECT(pipeline, "adding %" GST_PTR_FORMAT, new_sink);
                gst_bin_add(GST_BIN(pipeline), new_sink);

                GST_DEBUG_OBJECT(pipeline, "linking...");
                gst_element_link_many(parent, new_sink, NULL);

                gst_element_set_state(new_sink, GST_STATE_PLAYING);
                g_queue_push_tail(&sink[stream], new_sink);
        }

        GST_DEBUG_OBJECT(pipeline, "done.");
        gst_object_unref(parent);

        return GST_PAD_PROBE_REMOVE;
}

static gboolean cli_cb(GIOChannel *iochannel, GIOCondition cond, gpointer data)
{
        GMainLoop __attribute__((unused)) *loop = data;
        GError *error = NULL;
        gsize length;
        gsize terminator_pos;
        gchar *str_return;

        if (g_io_channel_read_line(iochannel, &str_return, &length, &terminator_pos, &error) == G_IO_STATUS_ERROR) {
                g_warning("Unable to read from stdin!\n");
        }

        if (NULL != error) {
                g_error("%s\n", error->message);
        }

        if (g_ascii_strncasecmp(str_return, "quit", 4) == 0) {
                g_main_loop_quit(loop);
        }
        if (g_ascii_strncasecmp(str_return, "1", 1) == 0) {
                gst_pad_add_probe(blockpad1, GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM, pad_probe_cb, data, NULL);
        }
        if (g_ascii_strncasecmp(str_return, "2", 1) == 0) {
                gst_pad_add_probe(blockpad2, GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM, pad_probe_cb, data, NULL);
        }
        if (g_ascii_strncasecmp(str_return, "3", 1) == 0) {
                gst_pad_add_probe(blockpad3, GST_PAD_PROBE_TYPE_BLOCK_DOWNSTREAM, pad_probe_cb, data, NULL);
        }

        g_printf("> ");
        return TRUE;
}

static gboolean bus_cb(GstBus *bus, GstMessage *msg, gpointer user_data)
{
        GMainLoop *loop = user_data;

        switch (GST_MESSAGE_TYPE(msg)) {
        case GST_MESSAGE_ERROR:
                {
                GError *err = NULL;
                gchar *dbg;

                gst_message_parse_error(msg, &err, &dbg);
                gst_object_default_error(msg->src, err, dbg);
                g_clear_error(&err);
                g_free(dbg);
                g_main_loop_quit(loop);
                break;
                }
        default:
                break;
        }
}

int main(int argc, char **argv)
{
        GMainLoop *loop;
        GstElement *src, *filter, *q1, *tee, *sink1, *sink2, *sink3;
        GstBus *bus;
        GIOChannel *iochannel;
        GError *error = NULL;
        guint source;

        gst_init(&argc, &argv);

        pipeline = gst_pipeline_new("pipeline");

        src = gst_element_factory_make("videotestsrc", NULL);
        g_object_set(src, "is-live", TRUE, NULL);

        filter = gst_element_factory_make("capsfilter", NULL);
        gst_util_set_object_arg(G_OBJECT(filter), "caps",
                        "video/x-raw, width=320, height=240, framerate=30/1, format=NV12");

        q1 = gst_element_factory_make("queue", NULL);

        tee = gst_element_factory_make("tee", "tee");

        q_stream1 = gst_element_factory_make("queue", "queue-stream-1");
        blockpad1 = gst_element_get_static_pad(q_stream1, "src");
        q_stream2 = gst_element_factory_make("queue", "queue-stream-2");
        blockpad2 = gst_element_get_static_pad(q_stream2, "src");
        q_stream3 = gst_element_factory_make("queue", "queue-stream-3");
        blockpad3 = gst_element_get_static_pad(q_stream3, "src");

        sink1 = gst_element_factory_make("fakesink", "fakesink1");
        if (sink1)
                g_queue_push_tail(&sink[0], sink1);
        sink2 = gst_element_factory_make("fakesink", "fakesink2");
        if (sink2)
                g_queue_push_tail(&sink[1], sink2);
        sink3 = gst_element_factory_make("fakesink", "fakesink3");
        if (sink3)
                g_queue_push_tail(&sink[2], sink3);

        gst_bin_add_many(GST_BIN(pipeline), src, filter, q1, tee, q_stream1, sink1, q_stream2, sink2, q_stream3, sink3, NULL);

        if (!gst_element_link_many(src, filter, tee, NULL) ||
            !gst_element_link_many(tee, q_stream1, sink1, NULL) ||
            !gst_element_link_many(tee, q_stream2, sink2, NULL) ||
            !gst_element_link_many(tee, q_stream3, sink3, NULL)) {
                g_error("Failed to link elements");
                return -2;
        }

        if (gst_element_set_state(pipeline, GST_STATE_PLAYING) == GST_STATE_CHANGE_FAILURE) {
                g_error("Error starting pipeline");
                return 1;
        }

        loop = g_main_loop_new(NULL, FALSE);
        gst_bus_add_watch(GST_ELEMENT_BUS(pipeline), bus_cb, loop);

        iochannel = g_io_channel_unix_new(STDIN_FILENO);
        g_io_channel_set_encoding(iochannel, NULL, &error);
        source = g_io_add_watch(iochannel, G_IO_IN, cli_cb, loop);
        g_print("> ");

        g_main_loop_run(loop);
        gst_element_set_state(pipeline, GST_STATE_NULL);
        g_source_remove(source);
        g_io_channel_unref(iochannel);
        gst_object_unref(blockpad1);
        gst_object_unref(blockpad2);
        gst_object_unref(blockpad3);
        gst_bus_remove_watch(GST_ELEMENT_BUS(pipeline));
        gst_object_unref(pipeline);
        g_main_loop_unref(loop);

        return 0;
}

我希望这对您有所帮助。

此致、

Bas Vermeulen