Gather and store chroma subsampling information for video content.

9 files changed, 79 insertions, 1 deletions

diff --git a/src/lib/dcp_examiner.h b/src/lib/dcp_examiner.h
index 66f694f72..4cc3e1240 100644
--- a/src/lib/dcp_examiner.h
+++ b/src/lib/dcp_examiner.h
@@ -58,6 +58,14 @@ public:
 		return false;
 	}
 
+	int log2_chroma_width () const {
+		return 0;
+	}
+
+	int log2_chroma_height () const {
+		return 0;
+	}
+
 	VideoRange range () const {
 		return VideoRange::FULL;
 	}
diff --git a/src/lib/ffmpeg_examiner.cc b/src/lib/ffmpeg_examiner.cc
index 853db90be..c63bca647 100644
--- a/src/lib/ffmpeg_examiner.cc
+++ b/src/lib/ffmpeg_examiner.cc
@@ -480,3 +480,18 @@ FFmpegExaminer::range () const
 		return VideoRange::FULL;
 	}
 }
+
+
+int
+FFmpegExaminer::log2_chroma_width () const
+{
+       return av_pix_fmt_desc_get(video_codec_context()->pix_fmt)->log2_chroma_w;
+}
+
+
+int
+FFmpegExaminer::log2_chroma_height () const
+{
+       return av_pix_fmt_desc_get(video_codec_context()->pix_fmt)->log2_chroma_h;
+}
+
diff --git a/src/lib/ffmpeg_examiner.h b/src/lib/ffmpeg_examiner.h
index 793460f9b..21fbac92a 100644
--- a/src/lib/ffmpeg_examiner.h
+++ b/src/lib/ffmpeg_examiner.h
@@ -42,6 +42,8 @@ public:
 	Frame video_length () const;
 	boost::optional<double> sample_aspect_ratio () const;
 	bool yuv () const;
+	int log2_chroma_width () const;
+	int log2_chroma_height () const;
 
 	std::vector<std::shared_ptr<FFmpegSubtitleStream>> subtitle_streams () const {
 		return _subtitle_streams;
diff --git a/src/lib/image_examiner.cc b/src/lib/image_examiner.cc
index 89d1517ce..624b05e57 100644
--- a/src/lib/image_examiner.cc
+++ b/src/lib/image_examiner.cc
@@ -107,3 +107,19 @@ ImageExaminer::yuv () const
 	*/
 	return false;
 }
+
+
+int
+ImageExaminer::log2_chroma_width () const
+{
+	/* See ::yuv() - we're assuming the image is not YUV and so not subsampled */
+	return 0;
+}
+
+
+int
+ImageExaminer::log2_chroma_height () const
+{
+	/* See ::yuv() - we're assuming the image is not YUV and so not subsampled */
+	return 0;
+}
diff --git a/src/lib/image_examiner.h b/src/lib/image_examiner.h
index cad8683a1..48d7770dc 100644
--- a/src/lib/image_examiner.h
+++ b/src/lib/image_examiner.h
@@ -39,6 +39,8 @@ public:
 	VideoRange range () const {
 		return VideoRange::FULL;
 	}
+	int log2_chroma_width () const;
+	int log2_chroma_height () const;
 
 private:
 	std::weak_ptr<const Film> _film;
diff --git a/src/lib/video_content.cc b/src/lib/video_content.cc
index 655b8baf6..c3e28fe09 100644
--- a/src/lib/video_content.cc
+++ b/src/lib/video_content.cc
@@ -184,6 +184,14 @@ VideoContent::VideoContent (Content* parent, cxml::ConstNodePtr node, int versio
 		_range = VideoRange::VIDEO;
 	}
 
+	if (auto cw = node->optional_number_child<int>("Log2ChromaWidth")) {
+		_log2_chroma_width = *cw;
+	}
+
+	if (auto ch = node->optional_number_child<int>("Log2ChromaHeight")) {
+		_log2_chroma_height = *ch;
+	}
+
 	auto burnt = node->optional_string_child("BurntSubtitleLanguage");
 	if (burnt) {
 		_burnt_subtitle_language = dcp::LanguageTag (*burnt);
@@ -192,7 +200,7 @@ VideoContent::VideoContent (Content* parent, cxml::ConstNodePtr node, int versio
 }
 
 
-VideoContent::VideoContent (Content* parent, vector<shared_ptr<Content> > c)
+VideoContent::VideoContent (Content* parent, vector<shared_ptr<Content>> c)
 	: ContentPart (parent)
 	, _length (0)
 	, _yuv (false)
@@ -243,6 +251,9 @@ VideoContent::VideoContent (Content* parent, vector<shared_ptr<Content> > c)
 		if (c[i]->video->yuv ()) {
 			_yuv = true;
 		}
+
+		_log2_chroma_width = std::max(_log2_chroma_width, c[i]->video->_log2_chroma_width);
+		_log2_chroma_height = std::max(_log2_chroma_height, c[i]->video->_log2_chroma_height);
 	}
 
 	_use = ref->use ();
@@ -285,6 +296,8 @@ VideoContent::as_xml (xmlpp::Node* node) const
 	node->add_child("FadeIn")->add_child_text (raw_convert<string> (_fade_in));
 	node->add_child("FadeOut")->add_child_text (raw_convert<string> (_fade_out));
 	node->add_child("Range")->add_child_text(_range == VideoRange::FULL ? "full" : "video");
+	node->add_child("Log2ChromaWidth")->add_child_text(raw_convert<string>(_log2_chroma_width));
+	node->add_child("Log2ChromaHeight")->add_child_text(raw_convert<string>(_log2_chroma_height));
 	if (_burnt_subtitle_language) {
 		node->add_child("BurntSubtitleLanguage")->add_child_text(_burnt_subtitle_language->to_string());
 	}
@@ -299,6 +312,8 @@ VideoContent::take_from_examiner (shared_ptr<VideoExaminer> d)
 	auto const ar = d->sample_aspect_ratio ();
 	auto const yuv = d->yuv ();
 	auto const range = d->range ();
+	auto const cw = d->log2_chroma_width ();
+	auto const ch = d->log2_chroma_height ();
 
 	ContentChangeSignaller cc1 (_parent, VideoContentProperty::SIZE);
 	ContentChangeSignaller cc2 (_parent, ContentProperty::LENGTH);
@@ -311,6 +326,8 @@ VideoContent::take_from_examiner (shared_ptr<VideoExaminer> d)
 		_sample_aspect_ratio = ar;
 		_yuv = yuv;
 		_range = range;
+		_log2_chroma_width = cw;
+		_log2_chroma_height = ch;
 	}
 
 	LOG_GENERAL ("Video length obtained from header as %1 frames", _length);
diff --git a/src/lib/video_content.h b/src/lib/video_content.h
index 0c4649954..31346ffcd 100644
--- a/src/lib/video_content.h
+++ b/src/lib/video_content.h
@@ -240,6 +240,8 @@ private:
 	/** Sample aspect ratio obtained from the content file's header, if there is one */
 	boost::optional<double> _sample_aspect_ratio;
 	bool _yuv;
+	int _log2_chroma_width = 0;
+	int _log2_chroma_height = 0;
 	/** fade in time in content frames */
 	Frame _fade_in;
 	/** fade out time in content frames */
diff --git a/src/lib/video_examiner.h b/src/lib/video_examiner.h
index 4e5c6dc0a..e83eb1adf 100644
--- a/src/lib/video_examiner.h
+++ b/src/lib/video_examiner.h
@@ -49,4 +49,14 @@ public:
 	/** @return true if this video is in YUV; must not be called if has_video() == false */
 	virtual bool yuv () const = 0;
 	virtual VideoRange range () const = 0;
+	/** @return Amount by which the luminance width must be shifted right to find the chroma width.
+	 *  e.g. for YUV420 or YUV422 this is 1, for YUV444 this is 0
+	 *  Must not be called if has_video() == false.
+	 */
+	virtual int log2_chroma_width () const = 0;
+	/** @return Amount by which the luminance height must be shifted right to find the chroma height.
+	 *  e.g. for YUV420 this is 1, for YUV444 this is 0
+	 *  Must not be called if has_video() == false.
+	 */
+	virtual int log2_chroma_height () const = 0;
 };
diff --git a/src/lib/video_mxf_examiner.h b/src/lib/video_mxf_examiner.h
index 37badafba..508cc9875 100644
--- a/src/lib/video_mxf_examiner.h
+++ b/src/lib/video_mxf_examiner.h
@@ -42,6 +42,12 @@ public:
 	VideoRange range () const {
 		return VideoRange::FULL;
 	}
+	int log2_chroma_width () const {
+		return 0;
+	}
+	int log2_chroma_height () const {
+		return 0;
+	}
 
 private:
 	std::shared_ptr<dcp::PictureAsset> _asset;