winegstreamer: Implement MF_LOW_LATENCY attribute and latency query.

dlls/winegstreamer/h264_decoder.c

@@ -88,6 +88,7 @@ static HRESULT try_create_wg_transform(struct h264_decoder *decoder)
     };
     struct wg_format input_format;
     struct wg_format output_format;
+    UINT32 low_latency;
 
     if (decoder->wg_transform)
         wg_transform_destroy(decoder->wg_transform);
@@ -109,6 +110,9 @@ static HRESULT try_create_wg_transform(struct h264_decoder *decoder)
     output_format.u.video.fps_d = 0;
     output_format.u.video.fps_n = 0;
 
+    if (SUCCEEDED(IMFAttributes_GetUINT32(decoder->attributes, &MF_LOW_LATENCY, &low_latency)))
+        attrs.low_latency = !!low_latency;
+
     if (!(decoder->wg_transform = wg_transform_create(&input_format, &output_format, &attrs)))
         return E_FAIL;
 

dlls/winegstreamer/unixlib.h

@@ -309,6 +309,7 @@ struct wg_transform_attrs
 {
     UINT32 output_plane_align;
     UINT32 input_queue_length;
+    BOOL low_latency;
 };
 
 struct wg_transform_create_params

dlls/winegstreamer/wg_transform.c

@@ -101,6 +101,26 @@ static GstFlowReturn transform_sink_chain_cb(GstPad *pad, GstObject *parent, Gst
     return GST_FLOW_OK;
 }
 
+static gboolean transform_src_query_latency(struct wg_transform *transform, GstQuery *query)
+{
+    GST_LOG("transform %p, query %p", transform, query);
+    gst_query_set_latency(query, transform->attrs.low_latency, 0, 0);
+    return true;
+}
+
+static gboolean transform_src_query_cb(GstPad *pad, GstObject *parent, GstQuery *query)
+{
+    struct wg_transform *transform = gst_pad_get_element_private(pad);
+
+    switch (query->type)
+    {
+    case GST_QUERY_LATENCY:
+        return transform_src_query_latency(transform, query);
+    default:
+        return gst_pad_query_default(pad, parent, query);
+    }
+}
+
 static gboolean transform_sink_query_cb(GstPad *pad, GstObject *parent, GstQuery *query)
 {
     struct wg_transform *transform = gst_pad_get_element_private(pad);
@@ -312,6 +332,9 @@ NTSTATUS wg_transform_create(void *args)
     if (!transform->my_src)
         goto out;
 
+    gst_pad_set_element_private(transform->my_src, transform);
+    gst_pad_set_query_function(transform->my_src, transform_src_query_cb);
+
     if (!(transform->output_caps = wg_format_to_caps(&output_format)))
         goto out;
     if (!(template = gst_pad_template_new("sink", GST_PAD_SINK, GST_PAD_ALWAYS, transform->output_caps)))