[FFmpeg-devel] [PoC][PATCH 08/14] avutil/frame: add a param change side data type

[James Almer <jamrial@gmail.com>]

Similar in purpose as the packet side data of the same name, but for encoders.

Signed-off-by: James Almer <jamrial@gmail.com>
---
An example of RefCount used for side data, including a copy and uninit callback
to handle allocations within the entry.

 libavutil/frame.h     | 14 ++++++++++++++
 libavutil/side_data.c | 23 +++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/libavutil/frame.h b/libavutil/frame.h
index 1feb11506a..c677407781 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -243,8 +243,22 @@ enum AVFrameSideDataType {
      * The data is an int storing the view ID.
      */
     AV_FRAME_DATA_VIEW_ID,
+
+    /**
+     * A side data used to signal an encoder that certain parameters changed.
+     * The payload is an AVParamChange struct.
+     */
+    AV_FRAME_DATA_PARAM_CHANGE,
 };
 
+typedef struct AVParamChange {
+    /**
+     * A dictionary filled with options to be passed to an already initialized
+     * encoder. May contain global and encoder private options.
+     */
+    AVDictionary *opts;
+} AVParamChange;
+
 enum AVActiveFormatDescription {
     AV_AFD_SAME         = 8,
     AV_AFD_4_3          = 9,
diff --git a/libavutil/side_data.c b/libavutil/side_data.c
index 597228baf1..c156d2bef8 100644
--- a/libavutil/side_data.c
+++ b/libavutil/side_data.c
@@ -63,6 +63,24 @@ typedef struct FFSideDataDescriptor {
     size_t size;
 } FFSideDataDescriptor;
 
+/* Type specific refstruct callbacks */
+
+static int copy_param_change(void *_dst, const void *_src)
+{
+    const AVParamChange *src = _src;
+    AVParamChange *dst = _dst;
+    int ret = av_dict_copy(&dst->opts, src->opts, 0);
+    if (ret < 0)
+        av_dict_free(&dst->opts);
+    return ret;
+}
+
+static void uninit_param_change(AVRefStructOpaque opaque, void *obj)
+{
+    AVParamChange *param = obj;
+    av_dict_free(&param->opts);
+}
+
 static const FFSideDataDescriptor sd_props[] = {
     [AV_FRAME_DATA_PANSCAN]                     = { .p = { "AVPanScan",                                    AV_SIDE_DATA_PROP_STRUCT | AV_SIDE_DATA_PROP_SIZE_DEPENDENT },
                                                     .size = sizeof(AVPanScan) },
@@ -88,6 +106,11 @@ static const FFSideDataDescriptor sd_props[] = {
     [AV_FRAME_DATA_DOVI_METADATA]               = { .p = { "Dolby Vision Metadata",                        AV_SIDE_DATA_PROP_COLOR_DEPENDENT } },
     [AV_FRAME_DATA_LCEVC]                       = { .p = { "LCEVC NAL data",                               AV_SIDE_DATA_PROP_SIZE_DEPENDENT } },
     [AV_FRAME_DATA_VIEW_ID]                     = { .p = { "View ID" } },
+    [AV_FRAME_DATA_PARAM_CHANGE]                = { .p = { "Param Change",                                 AV_SIDE_DATA_PROP_STRUCT },
+                                                    .props = FF_SIDE_DATA_PROP_REFSTRUCT,
+                                                    .copy = copy_param_change,
+                                                    .uninit = uninit_param_change,
+                                                    .size = sizeof(AVParamChange) },
     [AV_FRAME_DATA_STEREO3D]                    = { .p = { "Stereo 3D",                                    AV_SIDE_DATA_PROP_GLOBAL | AV_SIDE_DATA_PROP_STRUCT },
                                                     .size = sizeof(AVStereo3D) },
     [AV_FRAME_DATA_REPLAYGAIN]                  = { .p = { "AVReplayGain",                                 AV_SIDE_DATA_PROP_GLOBAL | AV_SIDE_DATA_PROP_STRUCT },
-- 
2.48.1

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