PR #25507 opened by Jake (jakefineman)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25507
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/25507.patch

Since 0cd75dbfa0 and 27e94281d1 added QueryInterface() implementations that 
compare against IID_IUnknown, building with --enable-decklink on macOS fails:

```
libavdevice/decklink_dec.cpp:138:43: error: use of undeclared identifier 
'IID_IUnknown'
libavdevice/decklink_dec.cpp:603:43: error: use of undeclared identifier 
'IID_IUnknown'
libavdevice/decklink_enc.cpp:120:39: error: use of undeclared identifier 
'IID_IUnknown'
libavdevice/decklink_enc.cpp:181:39: error: use of undeclared identifier 
'IID_IUnknown'
```

The Linux SDK defines IID_IUnknown in LinuxCOM.h and Windows gets it from the 
platform COM headers. The macOS SDK uses CoreFoundation's COM types from 
CFPlugInCOM.h, which only provide IUnknownUUID. This defines IID_IUnknown from 
it with CFUUIDGetUUIDBytes(), the same definition the macOS samples in the 
DeckLink SDK use (Examples/Mac/platform.h), so the GUID bytes are not 
duplicated. The definition is limited to __APPLE__, so Linux and Windows are 
unchanged.

This affects every release since n8.1.

Tested on macOS arm64 with Apple clang 21 and DeckLink SDK 16.0: all five 
libavdevice/decklink_* objects fail to compile before the patch and compile 
after it, and `ffmpeg -devices` lists decklink. I could not test capture or 
playback with a device.


>From f217768644d5775393c368fdc45b60ee4df8c684 Mon Sep 17 00:00:00 2001
From: Jake Fineman <[email protected]>
Date: Mon, 26 Oct 2026 22:39:23 -0400
Subject: [PATCH] avdevice/decklink: fix build on macOS by defining
 IID_IUnknown

Commits 0cd75dbfa0 and 27e94281d1 added QueryInterface()
implementations that compare the requested interface against
IID_IUnknown. The Linux SDK defines it in LinuxCOM.h and the Windows
SDK gets it from the platform COM headers, but the macOS SDK uses
CoreFoundation's COM types from <CoreFoundation/CFPlugInCOM.h>, which
only provide IUnknownUUID as a CFUUIDRef. Since then, building with
--enable-decklink on macOS fails:

  libavdevice/decklink_dec.cpp:138:43: error: use of undeclared
  identifier 'IID_IUnknown'
  libavdevice/decklink_dec.cpp:603:43: error: use of undeclared
  identifier 'IID_IUnknown'
  libavdevice/decklink_enc.cpp:120:39: error: use of undeclared
  identifier 'IID_IUnknown'
  libavdevice/decklink_enc.cpp:181:39: error: use of undeclared
  identifier 'IID_IUnknown'

On macOS, REFIID is CFUUIDBytes, so derive IID_IUnknown from
IUnknownUUID with CFUUIDGetUUIDBytes(), the same definition used by
the macOS samples shipped with the DeckLink SDK. This avoids
duplicating the GUID bytes, and CFUUIDGetConstantUUIDWithBytes()
returns a constant that must not be released. The definition is
limited to __APPLE__, so Linux and Windows builds are unchanged.

Tested with DeckLink SDK 16.0 and Apple clang 21 on macOS arm64.

Signed-off-by: Jake Fineman <[email protected]>
---
 libavdevice/decklink_common.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/libavdevice/decklink_common.h b/libavdevice/decklink_common.h
index 11430787ced..011c32dce49 100644
--- a/libavdevice/decklink_common.h
+++ b/libavdevice/decklink_common.h
@@ -103,6 +103,13 @@ static inline bool DECKLINK_IsEqualIID(const REFIID& 
riid1, const REFIID& riid2)
 }
 #endif
 
+#ifdef __APPLE__
+/* The macOS SDK uses CoreFoundation's COM types (CFPlugInCOM.h), which
+ * only provide IUnknownUUID as a CFUUIDRef, not IID_IUnknown as a REFIID
+ * like the Linux and Windows SDKs do. */
+#define IID_IUnknown CFUUIDGetUUIDBytes(IUnknownUUID)
+#endif
+
 class decklink_output_callback;
 class decklink_input_callback;
 
-- 
2.54.0

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