From 9e142b4410f9b1c703f3f12ced07c45dc2a0db24 Mon Sep 17 00:00:00 2001
From: Carl Hetherington <cth@carlh.net>
Date: Sun, 10 Dec 2023 16:20:20 +0100
Subject: Add FFmpegExaminer::has_alpha().

---
 src/lib/ffmpeg_examiner.cc | 13 +++++++++++++
 src/lib/ffmpeg_examiner.h  |  2 ++
 2 files changed, 15 insertions(+)

diff --git a/src/lib/ffmpeg_examiner.cc b/src/lib/ffmpeg_examiner.cc
index 46f4f236e..ed6f21094 100644
--- a/src/lib/ffmpeg_examiner.cc
+++ b/src/lib/ffmpeg_examiner.cc
@@ -383,6 +383,19 @@ FFmpegExaminer::bits_per_pixel () const
 }
 
 
+bool
+FFmpegExaminer::has_alpha() const
+{
+	if (video_codec_context()->pix_fmt == -1) {
+		return false;
+	}
+
+	auto const d = av_pix_fmt_desc_get(video_codec_context()->pix_fmt);
+	DCPOMATIC_ASSERT(d);
+	return d->flags & AV_PIX_FMT_FLAG_ALPHA;
+}
+
+
 bool
 FFmpegExaminer::yuv () const
 {
diff --git a/src/lib/ffmpeg_examiner.h b/src/lib/ffmpeg_examiner.h
index 10d060707..4747929b5 100644
--- a/src/lib/ffmpeg_examiner.h
+++ b/src/lib/ffmpeg_examiner.h
@@ -77,6 +77,8 @@ public:
 
 	boost::optional<int> bits_per_pixel () const;
 
+	bool has_alpha() const;
+
 	boost::optional<double> rotation () const {
 		return _rotation;
 	}
-- 
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