[PATCH v4 1/2] mf/sar: Query for current padding before requesting sample buffer.

[Giovanni Mascellani]

According to both MSDN and our impementation, GetBufferSize returns the
size of the buffer, but it doesn't guarantee that all of it is available.
In order to know how much of it is available, the caller must also call
GetCurrentPadding and subtract that number to the buffer size. Failing
to do so might result in GetBuffer returning an error.

Signed-off-by: Giovanni Mascellani 
---
This patch is unchanged. It is being resent because otherwise the second
patch fails to apply.

dlls/mf/sar.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/dlls/mf/sar.c b/dlls/mf/sar.c
index 77cbfcb21da..eba822ae0fe 100644
--- a/dlls/mf/sar.c
+++ b/dlls/mf/sar.c
@@ -1751,7 +1751,7 @@ static HRESULT WINAPI audio_renderer_render_callback_GetParameters(IMFAsyncCallb

static void audio_renderer_render(struct audio_renderer *renderer, IMFAsyncResult *result)
 {
-    unsigned int src_frames, dst_frames, max_frames, src_len;
+    unsigned int src_frames, dst_frames, max_frames, pad_frames, src_len;
     struct queued_object *obj, *obj2;
     BOOL keep_sample = FALSE;
     IMFMediaBuffer *buffer;
@@ -1775,20 +1775,24 @@ static void audio_renderer_render(struct audio_renderer *renderer, IMFAsyncResul
                     {
                         if (SUCCEEDED(IAudioClient_GetBufferSize(renderer->audio_client, &max_frames)))
                         {
-                            src_frames -= obj->u.sample.frame_offset;
-                            dst_frames = min(src_frames, max_frames);
-
-                            if (SUCCEEDED(hr = IAudioRenderClient_GetBuffer(renderer->audio_render_client, dst_frames, &dst)))
+                            if (SUCCEEDED(IAudioClient_GetCurrentPadding(renderer->audio_client, &pad_frames)))
                             {
-                                memcpy(dst, src + obj->u.sample.frame_offset * renderer->frame_size,
-                                        dst_frames * renderer->frame_size);
+                                max_frames -= pad_frames;
+                                src_frames -= obj->u.sample.frame_offset;
+                                dst_frames = min(src_frames, max_frames);

-                                IAudioRenderClient_ReleaseBuffer(renderer->audio_render_client, dst_frames, 0);
+                                if (SUCCEEDED(hr = IAudioRenderClient_GetBuffer(renderer->audio_render_client, dst_frames, &dst)))
+                                {
+                                    memcpy(dst, src + obj->u.sample.frame_offset * renderer->frame_size,
+                                            dst_frames * renderer->frame_size);

-                                obj->u.sample.frame_offset += dst_frames;
-                            }
+                                    IAudioRenderClient_ReleaseBuffer(renderer->audio_render_client, dst_frames, 0);

-                            keep_sample = FAILED(hr) || src_frames > max_frames;
+                                    obj->u.sample.frame_offset += dst_frames;
+                                }
+
+                                keep_sample = FAILED(hr) || src_frames > max_frames;
+                            }
                         }
                     }
                     IMFMediaBuffer_Unlock(buffer);