How to retrieve attached custom meta information on receiver side?

[Борис]

Hi. I added my custom meta data and can't retrieve it on receiver side
On sender side i have rtsp server and i'm adding meta info to frame buffers
(i skip some of not important parts of code):

    buffer = gst_buffer_new_wrapped(frame.data, size);
...
        GST_BUFFER_PTS (buffer) = ts;
        GST_BUFFER_DTS (buffer) = ts;

        qint64 duration = ((double)1 / params.framerate) * GST_SECOND;
        GST_BUFFER_DURATION(buffer) = duration;
        GST_BUFFER_OFFSET(buffer) = currentFrameCount;

        // ADD META
        GstMetaMarking* meta = GST_META_MARKING_ADD(buffer);
        meta->in_timestamp = it->time;
        if (currentFrameCount >= needFrameCount)
        {
            meta->last = true;
        }
        else
        {
            meta->last = false;
        }
      // here i check that meta added correctly
        GstMetaMarking* metaCheck = GST_META_MARKING_GET(buffer);
        qDebug() << metaCheck->in_timestamp << metaCheck->last;
        g_signal_emit_by_name (appsrc, "push-buffer", buffer, &ret);
        gst_buffer_unref (buffer);

On receiver side i modified part where i retrieve frame:
...
sample = gst_app_sink_pull_sample(GST_APP_SINK(sink));
...
GstBuffer * buf = gst_sample_get_buffer(sample);
if (!buf)
        return false;

// RETRIEVE META
GstMetaMarking* meta = GST_META_MARKING_GET(buf);
if (meta)
{
CV_WARN("GStreamer: META EXISTS");
tsMeta = meta->in_timestamp;
isLastMeta = meta->last;
}
else
{
CV_WARN("GStreamer: META IS EMPTY"); // so i'm always here
}
    GstMapInfo info;
    if (!gst_buffer_map(buf, &info, GST_MAP_READ))
    {
        //something weird went wrong here. abort. abort.
        CV_WARN("Failed to map GStreamerbuffer to system memory");
        return false;
    }

    {
        Mat src;
        if (isOutputByteBuffer)
            src = Mat(Size(info.size, 1), CV_8UC1, info.data);
        else
            src = Mat(sz, CV_MAKETYPE(CV_8U, channels), info.data);
        CV_Assert(src.isContinuous());
        src.copyTo(dst);
    }
    gst_buffer_unmap(buf, &info);



So, here
  GstMetaMarking* meta = GST_META_MARKING_GET(buf);

i always get empty pointer. What is wrong here?
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