Add transformation matrix API.

Add AV_PKT_DATA_DISPLAYMATRIX and AV_FRAME_DATA_DISPLAYMATRIX as stream and
frame side data (respectively) to describe a display transformation matrix
for linear transformation operations on the decoded video.

Add functions to easily extract a rotation angle from a matrix and
conversely to setup a matrix for a given rotation angle.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

2 files changed, 18 insertions, 0 deletions

diff --git a/libavcodec/avcodec.h b/libavcodec/avcodec.h
index 5640710850..f8d815f69b 100644
--- a/libavcodec/avcodec.h
+++ b/libavcodec/avcodec.h
@@ -959,6 +959,15 @@ enum AVPacketSideDataType {
      * ReplayGain information in form of the AVReplayGain struct.
      */
     AV_PKT_DATA_REPLAYGAIN,
+
+    /**
+     * This side data contains a 3x3 transformation matrix describing an affine
+     * transformation that needs to be applied to the decoded video frames for
+     * correct presentation.
+     *
+     * See libavutil/display.h for a detailed description of the data.
+     */
+    AV_PKT_DATA_DISPLAYMATRIX,
 };
 
 typedef struct AVPacketSideData {
diff --git a/libavcodec/utils.c b/libavcodec/utils.c
index 71cbc57b44..cb456d5ae0 100644
--- a/libavcodec/utils.c
+++ b/libavcodec/utils.c
@@ -598,6 +598,15 @@ int ff_decode_frame_props(AVCodecContext *avctx, AVFrame *frame)
 
         memcpy(frame_sd->data, packet_sd, size);
     }
+    /* copy the displaymatrix to the output frame */
+    packet_sd = av_packet_get_side_data(pkt, AV_PKT_DATA_DISPLAYMATRIX, &size);
+    if (packet_sd) {
+        frame_sd = av_frame_new_side_data(frame, AV_FRAME_DATA_DISPLAYMATRIX, size);
+        if (!frame_sd)
+            return AVERROR(ENOMEM);
+
+        memcpy(frame_sd->data, packet_sd, size);
+    }
 
     return 0;
 }