From 6b758d46f6e915cf7fa4ee83de9786e7a56d0022 Mon Sep 17 00:00:00 2001
From: "feliks.pobiedzinski@swmansion.com" <feliks.pobiedzinski@swmansion.com>
Date: Thu, 2 Jan 2025 16:10:43 +0100
Subject: [PATCH 1/2] Implement initial auto demand WiP

---
 .../core/element/auto_flow_controller.ex      | 49 ++++++++++++-------
 1 file changed, 31 insertions(+), 18 deletions(-)

diff --git a/lib/membrane/core/element/auto_flow_controller.ex b/lib/membrane/core/element/auto_flow_controller.ex
index 36c6fc3e1..02c8a8850 100644
--- a/lib/membrane/core/element/auto_flow_controller.ex
+++ b/lib/membrane/core/element/auto_flow_controller.ex
@@ -18,6 +18,7 @@ defmodule Membrane.Core.Element.AutoFlowController do
   require Membrane.Pad, as: Pad
 
   @empty_map_set MapSet.new()
+  @initial_auto_demand 20
 
   # Description of the auto flow control queueing mechanism
 
@@ -177,23 +178,25 @@ defmodule Membrane.Core.Element.AutoFlowController do
   end
 
   defp do_auto_adjust_atomic_demand(pad_data, state) when is_input_auto_pad_data(pad_data) do
-    if increase_atomic_demand?(pad_data, state) do
-      %{
-        ref: ref,
-        auto_demand_size: auto_demand_size,
-        demand: demand,
-        atomic_demand: atomic_demand,
-        stalker_metrics: stalker_metrics
-      } = pad_data
+    case atomic_demand_target_value(pad_data, state) do
+      target_value when is_number(target_value) ->
+        %{
+          ref: ref,
+          demand: demand,
+          atomic_demand: atomic_demand,
+          stalker_metrics: stalker_metrics
+        } = pad_data
 
-      diff = auto_demand_size - demand
-      :ok = AtomicDemand.increase(atomic_demand, diff)
+        diff = target_value - demand
+        :ok = AtomicDemand.increase(atomic_demand, diff)
 
-      :atomics.put(stalker_metrics.demand, 1, auto_demand_size)
+        :atomics.put(stalker_metrics.demand, 1, target_value)
 
-      PadModel.set_data!(state, ref, :demand, auto_demand_size)
-    else
-      state
+        state
+        |> PadModel.set_data!(ref, :demand, target_value)
+
+      :pass ->
+        state
     end
   end
 
@@ -201,11 +204,21 @@ defmodule Membrane.Core.Element.AutoFlowController do
     raise "#{__MODULE__}.auto_adjust_atomic_demand/2 can be called only for auto input pads, while #{inspect(ref)} is not such a pad."
   end
 
-  defp increase_atomic_demand?(pad_data, state) do
-    state.effective_flow_control == :pull and
-      not pad_data.auto_demand_paused? and
+  defp atomic_demand_target_value(pad_data, state) do
+    cond do
+      state.effective_flow_control == :push or pad_data.auto_demand_paused? ->
+        :pass
+
       pad_data.demand < pad_data.auto_demand_size / 2 and
-      state.satisfied_auto_output_pads == @empty_map_set
+        state.satisfied_auto_output_pads == @empty_map_set ->
+        pad_data.auto_demand_size
+
+      not pad_data.start_of_stream? and pad_data.demand == 0 ->
+        pad_data.auto_demand_size |> min(@initial_auto_demand)
+
+      true ->
+        :pass
+    end
   end
 
   @spec pop_queues_and_bump_demand(State.t()) :: State.t()

From 386eeaa34adf05983fac41bd1b53d1a7ae47892d Mon Sep 17 00:00:00 2001
From: "feliks.pobiedzinski@swmansion.com" <feliks.pobiedzinski@swmansion.com>
Date: Thu, 2 Jan 2025 16:13:36 +0100
Subject: [PATCH 2/2] Mix format

---
 lib/membrane/core/element/auto_flow_controller.ex | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/membrane/core/element/auto_flow_controller.ex b/lib/membrane/core/element/auto_flow_controller.ex
index 02c8a8850..e58669378 100644
--- a/lib/membrane/core/element/auto_flow_controller.ex
+++ b/lib/membrane/core/element/auto_flow_controller.ex
@@ -210,7 +210,7 @@ defmodule Membrane.Core.Element.AutoFlowController do
         :pass
 
       pad_data.demand < pad_data.auto_demand_size / 2 and
-        state.satisfied_auto_output_pads == @empty_map_set ->
+          state.satisfied_auto_output_pads == @empty_map_set ->
         pad_data.auto_demand_size
 
       not pad_data.start_of_stream? and pad_data.demand == 0 ->