[FFmpeg-devel] [PATCH 1/4] avutil: add generic side data for video coding info

* [FFmpeg-devel] [PATCH 1/4] avutil: add generic side data for video coding info
@ 2025-07-18 10:30 Timothée Regaud
  2025-07-18 10:30 ` [FFmpeg-devel] [PATCH 2/4] avcodec: add option to export " Timothée Regaud
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: Timothée Regaud @ 2025-07-18 10:30 UTC (permalink / raw)
  To: ffmpeg-devel; +Cc: Timothee Regaud

From: Timothee Regaud <timothee.informatique@regaud-chapuy.fr>

Adds the generic data structures to libavutil. The design is recursive to support other codecs, even though the implementation is only for H.264 for now.

Signed-off-by: Timothee Regaud <timothee.informatique@regaud-chapuy.fr>
---
 libavutil/Makefile            |   1 +
 libavutil/frame.h             |   7 ++
 libavutil/side_data.c         |   1 +
 libavutil/video_coding_info.h | 163 ++++++++++++++++++++++++++++++++++
 4 files changed, 172 insertions(+)
 create mode 100644 libavutil/video_coding_info.h

diff --git a/libavutil/Makefile b/libavutil/Makefile
index 94a56bb72f..44e51ab7ae 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -93,6 +93,7 @@ HEADERS = adler32.h                                                     \
           tree.h                                                        \
           twofish.h                                                     \
           uuid.h                                                        \
+          video_coding_info.h                                           \
           version.h                                                     \
           video_enc_params.h                                            \
           xtea.h                                                        \
diff --git a/libavutil/frame.h b/libavutil/frame.h
index c50cd263d9..f4404472a0 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -254,6 +254,13 @@ enum AVFrameSideDataType {
      * libavutil/tdrdi.h.
      */
     AV_FRAME_DATA_3D_REFERENCE_DISPLAYS,
+
+    /**
+     * Detailed block-level coding information. The data is an AVVideoCodingInfo
+     * structure. This is exported by video decoders and can be used by filters
+     * for analysis and visualization.
+     */
+    AV_FRAME_DATA_VIDEO_CODING_INFO,
 };
 
 enum AVActiveFormatDescription {
diff --git a/libavutil/side_data.c b/libavutil/side_data.c
index fa2a2c2a13..b938ef6f52 100644
--- a/libavutil/side_data.c
+++ b/libavutil/side_data.c
@@ -56,6 +56,7 @@ static const AVSideDataDescriptor sd_props[] = {
     [AV_FRAME_DATA_SEI_UNREGISTERED]            = { "H.26[45] User Data Unregistered SEI message",  AV_SIDE_DATA_PROP_MULTI },
     [AV_FRAME_DATA_VIDEO_HINT]                  = { "Encoding video hint",                          AV_SIDE_DATA_PROP_SIZE_DEPENDENT },
     [AV_FRAME_DATA_3D_REFERENCE_DISPLAYS]       = { "3D Reference Displays Information",            AV_SIDE_DATA_PROP_GLOBAL },
+    [AV_FRAME_DATA_VIDEO_CODING_INFO]           = { "Video Coding Info",                            AV_SIDE_DATA_PROP_SIZE_DEPENDENT },
 };
 
 const AVSideDataDescriptor *av_frame_side_data_desc(enum AVFrameSideDataType type)
diff --git a/libavutil/video_coding_info.h b/libavutil/video_coding_info.h
new file mode 100644
index 0000000000..17e9345892
--- /dev/null
+++ b/libavutil/video_coding_info.h
@@ -0,0 +1,163 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_VIDEO_CODING_INFO_H
+#define AVUTIL_VIDEO_CODING_INFO_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+/**
+ * @file
+ * @ingroup lavu_frame
+ * Structures for describing block-level video coding information.
+ */
+
+/**
+ * @defgroup lavu_video_coding_info Video Coding Info
+ * @ingroup lavu_frame
+ *
+ * @{
+ * Structures for describing block-level video coding information, to be
+ * attached to an AVFrame as side data.
+ *
+ * All pointer-like members in these structures are offsets relative to the
+ * start of the AVVideoCodingInfo struct to ensure the side data is
+ * self-contained and relocatable. This is critical as the underlying buffer
+ * may be moved in memory.
+ */
+
+/**
+ * Structure to hold inter-prediction information for a block.
+ */
+typedef struct AVBlockInterInfo {
+    /**
+     * Offsets to motion vectors for list 0 and list 1, relative to the
+     * start of the AVVideoCodingInfo struct.
+     * The data for each list is an array of [x, y] pairs of int16_t.
+     * The number of vectors is given by num_mv.
+     * An offset of 0 indicates this data is not present.
+     */
+    size_t mv_offset[2];
+
+    /**
+     * Offsets to reference indices for list 0 and list 1, relative to the
+     * start of the AVVideoCodingInfo struct.
+     * The data is an array of int8_t. A value of -1 indicates the reference
+     * is not used for a specific partition.
+     * An offset of 0 indicates this data is not present.
+     */
+    size_t ref_idx_offset[2];
+    /**
+     * Number of motion vectors for list 0 and list 1.
+     */
+    uint8_t num_mv[2];
+} AVBlockInterInfo;
+
+/**
+ * Structure to hold intra-prediction information for a block.
+ */
+typedef struct AVBlockIntraInfo {
+    /**
+     * Offset to an array of intra prediction modes, relative to the
+     * start of the AVVideoCodingInfo struct.
+     * The number of modes is given by num_pred_modes.
+     */
+    size_t pred_mode_offset;
+
+    /**
+     * Number of intra prediction modes.
+     */
+    uint8_t num_pred_modes;
+
+    /**
+     * Chroma intra prediction mode.
+     */
+    uint8_t chroma_pred_mode;
+} AVBlockIntraInfo;
+
+/**
+ * Main structure for a single coding block.
+ * This structure can be recursive for codecs that use tree-based partitioning.
+ */
+typedef struct AVVideoCodingInfoBlock {
+    /**
+     * Position (x, y) and size (w, h) of the block, in pixels,
+     * relative to the top-left corner of the frame.
+     */
+    int16_t x, y;
+    uint8_t w, h;
+
+    /**
+     * Flag indicating if the block is intra-coded.
+     * 1 if intra, 0 if inter.
+     */
+    uint8_t is_intra;
+
+    /**
+     * The original, codec-specific type of this block or macroblock.
+     * This allows a filter to have codec-specific logic for interpreting
+     * the generic prediction information based on the source codec.
+     * For example, for H.264, this would store the MB type flags (MB_TYPE_*).
+     */
+    uint32_t codec_specific_type;
+
+    union {
+        AVBlockIntraInfo intra;
+        AVBlockInterInfo inter;
+    };
+
+    /**
+     * Number of child blocks this block is partitioned into.
+     * If 0, this is a leaf node in the partition tree.
+     */
+    uint8_t num_children;
+
+    /**
+     * Offset to an array of child AVVideoCodingInfoBlock structures, relative
+     * to the start of the AVVideoCodingInfo struct.
+     * This allows for recursive representation of coding structures.
+     * An offset of 0 indicates there are no children.
+     */
+    size_t children_offset;
+} AVVideoCodingInfoBlock;
+
+/**
+ * Top-level structure to be attached to an AVFrame as side data.
+ * It contains an array of the highest-level coding blocks (e.g., CTUs or MBs).
+ */
+typedef struct AVVideoCodingInfo {
+    /**
+     * Number of top-level blocks in the frame.
+     */
+    uint32_t nb_blocks;
+
+    /**
+     * Offset to an array of top-level blocks, relative to the start of the
+     * AVVideoCodingInfo struct.
+     * The actual data for these blocks, and any child blocks or sub-data,
+     * is stored contiguously in the AVBufferRef attached to the side data.
+     */
+    size_t blocks_offset;
+} AVVideoCodingInfo;
+
+/**
+ * @}
+ */
+
+#endif /* AVUTIL_VIDEO_CODING_INFO_H */
-- 
2.39.5

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