lavu/frame: add QP side data

This adds a way for an API user to transfer QP data and metadata without
having to keep the reference to AVFrame, and without having to
explicitly care about QP APIs. It might also provide a way to finally
remove the deprecated QP related fields. In the end, the QP table should
be handled in a very similar way to e.g. AV_FRAME_DATA_MOTION_VECTORS.

There are two side data types, because I didn't care about having to
repack the QP data so the table and the metadata are in a single
AVBufferRef. Otherwise it would have either required a copy on decoding
(extra slowdown for something as obscure as the QP data), or would have
required making intrusive changes to the codecs which support export of
this data.

The new side data types are added under deprecation guards, because I
don't intend to change the status of the QP export as being deprecated
(as it was before this patch too).

3 files changed, 71 insertions, 7 deletions

diff --git a/libavutil/frame.c b/libavutil/frame.c
index 0db2a2d57b..ea13cd3ed6 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -46,8 +46,17 @@ MAKE_ACCESSORS(AVFrame, frame, enum AVColorRange, color_range)
                av_get_channel_layout_nb_channels((frame)->channel_layout))
 
 #if FF_API_FRAME_QP
+struct qp_properties {
+    int stride;
+    int type;
+};
+
 int av_frame_set_qp_table(AVFrame *f, AVBufferRef *buf, int stride, int qp_type)
 {
+    struct qp_properties *p;
+    AVFrameSideData *sd;
+    AVBufferRef *ref;
+
 FF_DISABLE_DEPRECATION_WARNINGS
     av_buffer_unref(&f->qp_table_buf);
 
@@ -57,20 +66,56 @@ FF_DISABLE_DEPRECATION_WARNINGS
     f->qscale_type  = qp_type;
 FF_ENABLE_DEPRECATION_WARNINGS
 
+    av_frame_remove_side_data(f, AV_FRAME_DATA_QP_TABLE_PROPERTIES);
+    av_frame_remove_side_data(f, AV_FRAME_DATA_QP_TABLE_DATA);
+
+    ref = av_buffer_ref(buf);
+    if (!av_frame_new_side_data_from_buf(f, AV_FRAME_DATA_QP_TABLE_DATA, ref)) {
+        av_buffer_unref(&ref);
+        return AVERROR(ENOMEM);
+    }
+
+    sd = av_frame_new_side_data(f, AV_FRAME_DATA_QP_TABLE_PROPERTIES,
+                                sizeof(struct qp_properties));
+    if (!sd)
+        return AVERROR(ENOMEM);
+
+    p = (struct qp_properties *)sd->data;
+    p->stride = stride;
+    p->type = qp_type;
+
     return 0;
 }
 
 int8_t *av_frame_get_qp_table(AVFrame *f, int *stride, int *type)
 {
-FF_DISABLE_DEPRECATION_WARNINGS
-    *stride = f->qstride;
-    *type   = f->qscale_type;
+    AVBufferRef *buf = NULL;
 
-    if (!f->qp_table_buf)
-        return NULL;
+    *stride = 0;
+    *type   = 0;
 
-    return f->qp_table_buf->data;
+FF_DISABLE_DEPRECATION_WARNINGS
+    if (f->qp_table_buf) {
+        *stride = f->qstride;
+        *type   = f->qscale_type;
+        buf     = f->qp_table_buf;
 FF_ENABLE_DEPRECATION_WARNINGS
+    } else {
+        AVFrameSideData *sd;
+        struct qp_properties *p;
+        sd = av_frame_get_side_data(f, AV_FRAME_DATA_QP_TABLE_PROPERTIES);
+        if (!sd)
+            return NULL;
+        p = (struct qp_properties *)sd->data;
+        sd = av_frame_get_side_data(f, AV_FRAME_DATA_QP_TABLE_DATA);
+        if (!sd)
+            return NULL;
+        *stride = p->stride;
+        *type   = p->type;
+        buf     = sd->buf;
+    }
+
+    return buf ? buf->data : NULL;
 }
 #endif
 
@@ -787,6 +832,8 @@ const char *av_frame_side_data_name(enum AVFrameSideDataType type)
     case AV_FRAME_DATA_CONTENT_LIGHT_LEVEL:         return "Content light level metadata";
     case AV_FRAME_DATA_GOP_TIMECODE:                return "GOP timecode";
     case AV_FRAME_DATA_ICC_PROFILE:                 return "ICC profile";
+    case AV_FRAME_DATA_QP_TABLE_PROPERTIES:         return "QP table properties";
+    case AV_FRAME_DATA_QP_TABLE_DATA:               return "QP table data";
     }
     return NULL;
 }
diff --git a/libavutil/frame.h b/libavutil/frame.h
index ddbac3156d..9d57d6ce66 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -141,6 +141,23 @@ enum AVFrameSideDataType {
      * metadata key entry "name".
      */
     AV_FRAME_DATA_ICC_PROFILE,
+
+#if FF_API_FRAME_QP
+    /**
+     * Implementation-specific description of the format of AV_FRAME_QP_TABLE_DATA.
+     * The contents of this side data are undocumented and internal; use
+     * av_frame_set_qp_table() and av_frame_get_qp_table() to access this in a
+     * meaningful way instead.
+     */
+    AV_FRAME_DATA_QP_TABLE_PROPERTIES,
+
+    /**
+     * Raw QP table data. Its format is described by
+     * AV_FRAME_DATA_QP_TABLE_PROPERTIES. Use av_frame_set_qp_table() and
+     * av_frame_get_qp_table() to access this instead.
+     */
+    AV_FRAME_DATA_QP_TABLE_DATA,
+#endif
 };
 
 enum AVActiveFormatDescription {
diff --git a/libavutil/version.h b/libavutil/version.h
index 9ca556ddc9..d166bb30e7 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -79,7 +79,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  56
-#define LIBAVUTIL_VERSION_MINOR  10
+#define LIBAVUTIL_VERSION_MINOR  11
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \