[PATCH 0/1] MR6848: mf/evr: Increase the number of prerolled samples to 3.

[Rémi Bernon (＠rbernon)]

Fixes some stuttering in Secret of Mana.

Native seems to only preroll 2 samples, but it still stutters a bit in
Secret of Mana without at least 3 buffers. This is probably caused by
a different sample decoding pattern, and 3 buffers in flight should be
fine.

[PATCH 1/1] mf/evr: Increase the number of prerolled samples to 3.

[Rémi Bernon]

From: Rémi Bernon

Fixes some stuttering in Secret of Mana.

Native seems to only preroll 2 samples, but it still stutters a bit in
Secret of Mana without at least 3 buffers. This is probably caused by
a different sample decoding pattern, and 3 buffers in flight should be
fine.
---
 dlls/mf/evr.c     | 15 ++++++++++++---
 dlls/mf/session.c |  2 +-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/dlls/mf/evr.c b/dlls/mf/evr.c
index db7053a1405..5ac526c9651 100644
--- a/dlls/mf/evr.c
+++ b/dlls/mf/evr.c
@@ -64,6 +64,7 @@ struct video_stream
     LONG refcount;
     unsigned int id;
     unsigned int flags;
+    unsigned int preroll_count;
     struct video_renderer *parent;
     IMFMediaEventQueue *event_queue;
     IMFVideoSampleAllocator *allocator;
@@ -420,9 +421,16 @@ static HRESULT WINAPI video_stream_sink_ProcessSample(IMFStreamSink *iface, IMFS

if (stream->flags & EVR_STREAM_PREROLLING)
         {
-            IMFMediaEventQueue_QueueEventParamVar(stream->event_queue, MEStreamSinkPrerolled, &GUID_NULL, S_OK, NULL);
-            stream->flags &= ~EVR_STREAM_PREROLLING;
-            stream->flags |= EVR_STREAM_PREROLLED;
+            if (stream->preroll_count--)
+                IMFMediaEventQueue_QueueEventParamVar(stream->event_queue, MEStreamSinkRequestSample,
+                        &GUID_NULL, S_OK, NULL);
+            else
+            {
+                IMFMediaEventQueue_QueueEventParamVar(stream->event_queue, MEStreamSinkPrerolled,
+                        &GUID_NULL, S_OK, NULL);
+                stream->flags &= ~EVR_STREAM_PREROLLING;
+                stream->flags |= EVR_STREAM_PREROLLED;
+            }
         }
     }

@@ -1528,6 +1536,7 @@ static HRESULT WINAPI video_renderer_preroll_NotifyPreroll(IMFMediaSinkPreroll *
                 IMFMediaEventQueue_QueueEventParamVar(stream->event_queue, MEStreamSinkRequestSample,
                         &GUID_NULL, S_OK, NULL);
                 stream->flags |= EVR_STREAM_PREROLLING;
+                stream->preroll_count = 3;
             }
             LeaveCriticalSection(&stream->cs);
         }
diff --git a/dlls/mf/session.c b/dlls/mf/session.c
index 3c989249229..d01f2728782 100644
--- a/dlls/mf/session.c
+++ b/dlls/mf/session.c
@@ -1798,7 +1798,7 @@ static HRESULT session_append_node(struct media_session *session, IMFTopologyNod
                         &IID_IMFVideoSampleAllocator, (void **)&topo_node->u.sink.allocator)))
                     {
                         if (FAILED(hr = IMFVideoSampleAllocator_InitializeSampleAllocator(topo_node->u.sink.allocator,
-                                2, media_type)))
+                                4, media_type)))
                         {
                             WARN("Failed to initialize sample allocator for the stream, hr %#lx.\n", hr);
                         }

[Nikolay Sivov (＠nsivov)]

So, is this basically a workaround for some slowness of the pipeline? Do you know why it helps? Does it stutter when starting playback or all the way through?

[Rémi Bernon (＠rbernon)]

I don't know exactly but the stutter started happening after 8ffebcf4ab869bf1067b23f3a67eead0213494c6. It does seem right to me to have more than one buffer in flight in any case, as using a single buffer will just stall the pipeline while the application is handling the current frame.