[FFmpeg-devel] [PATCH 1/6] avutil/frame: add av_frame_remove_side_data_changed

[Niklas Haas <ffmpeg@haasn.xyz>]

From: Niklas Haas <git@haasn.dev>

Many filters modify certain aspects of frame data, e.g. through resizing
(vf_*scale* family), color volume mapping (vf_lut*, vf_tonemap*), or
possibly others.

When this happens, we should strip all frame side data that will no
longer be correct/relevant after the operation. For example, changing
the image size should invalidate AV_FRAME_DATA_PANSCAN because the crop
window (given in pixels) no longer corresponds to the actual image size.
For another example, tone-mapping filters (e.g. from HDR to SDR) should
strip all of the dynamic HDR related metadata.

Since there are a lot of similar with basically similar operations, it
make sense to consolidate this stripping logic into a common helper
function. I decided to put it into libavutil as it may be useful for API
users as well, who often have their own internal processing and
filtering.
---
 doc/APIchanges      |  3 +++
 libavutil/frame.c   | 31 +++++++++++++++++++++++++++++++
 libavutil/frame.h   | 14 ++++++++++++++
 libavutil/version.h |  2 +-
 4 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index 0566fcdcc5..26af725528 100644
--- a/doc/APIchanges
+++ b/doc/APIchanges
@@ -2,6 +2,9 @@ The last version increases of all libraries were on 2024-03-07
 
 API changes, most recent first:
 
+2024-04-xx - xxxxxxxxxx - lavu 59.17.100 - frame.h
+  Add av_frame_remove_side_data_changed().
+
 2024-04-24 - 8616cfe0890 - lavu 59.16.100 - opt.h
   Add AV_OPT_SERIALIZE_SEARCH_CHILDREN.
 
diff --git a/libavutil/frame.c b/libavutil/frame.c
index 0775e2abd9..d5482c258e 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -1015,6 +1015,37 @@ void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type)
     remove_side_data(&frame->side_data, &frame->nb_side_data, type);
 }
 
+static const struct {
+    enum AVFrameSideDataType type;
+    int aspect;
+} side_data_aspects[] = {
+    { AV_FRAME_DATA_PANSCAN,                    AV_FRAME_CHANGED_SIZE },
+    { AV_FRAME_DATA_MOTION_VECTORS,             AV_FRAME_CHANGED_SIZE },
+    { AV_FRAME_DATA_MASTERING_DISPLAY_METADATA, AV_FRAME_CHANGED_COLOR_VOLUME },
+
+    { AV_FRAME_DATA_SPHERICAL,                  AV_FRAME_CHANGED_SIZE },
+    { AV_FRAME_DATA_CONTENT_LIGHT_LEVEL,        AV_FRAME_CHANGED_COLOR_VOLUME },
+    { AV_FRAME_DATA_ICC_PROFILE,                AV_FRAME_CHANGED_COLOR_VOLUME },
+    { AV_FRAME_DATA_DYNAMIC_HDR_PLUS,           AV_FRAME_CHANGED_COLOR_VOLUME },
+    { AV_FRAME_DATA_REGIONS_OF_INTEREST,        AV_FRAME_CHANGED_SIZE },
+    { AV_FRAME_DATA_DETECTION_BBOXES,           AV_FRAME_CHANGED_SIZE },
+    { AV_FRAME_DATA_DOVI_RPU_BUFFER,            AV_FRAME_CHANGED_COLOR_VOLUME },
+    { AV_FRAME_DATA_DOVI_METADATA,              AV_FRAME_CHANGED_COLOR_VOLUME },
+    { AV_FRAME_DATA_DYNAMIC_HDR_VIVID,          AV_FRAME_CHANGED_COLOR_VOLUME },
+    { AV_FRAME_DATA_VIDEO_HINT,                 AV_FRAME_CHANGED_SIZE },
+};
+
+void av_frame_remove_side_data_changed(AVFrame *frame, int changed_aspects)
+{
+    if (!changed_aspects)
+        return;
+
+    for (int i = 0; i < FF_ARRAY_ELEMS(side_data_aspects); i++) {
+        if (changed_aspects & side_data_aspects[i].aspect)
+            av_frame_remove_side_data(frame, side_data_aspects[i].type);
+    }
+}
+
 const AVSideDataDescriptor *av_frame_side_data_desc(enum AVFrameSideDataType type)
 {
     unsigned t = type;
diff --git a/libavutil/frame.h b/libavutil/frame.h
index 60bb966f8b..7e07ecf91f 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -983,6 +983,20 @@ AVFrameSideData *av_frame_get_side_data(const AVFrame *frame,
  */
 void av_frame_remove_side_data(AVFrame *frame, enum AVFrameSideDataType type);
 
+/**
+ * Flags for stripping side data based on changed aspects.
+ */
+enum {
+    /* Video only */
+    AV_FRAME_CHANGED_SIZE           = 1 << 0, ///< changed dimensions / crop
+    AV_FRAME_CHANGED_COLOR_VOLUME   = 1 << 1, ///< changed color volume
+};
+
+/**
+ * Remove all relevant side data after a corresponding change to the frame
+ * data, based on the given bitset of frame aspects.
+ */
+void av_frame_remove_side_data_changed(AVFrame *frame, int changed_aspects);
 
 /**
  * Flags for frame cropping.
diff --git a/libavutil/version.h b/libavutil/version.h
index ea289c406f..3b5a2e7aaa 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  59
-#define LIBAVUTIL_VERSION_MINOR  16
+#define LIBAVUTIL_VERSION_MINOR  17
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \
-- 
2.44.0

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