libavcodec/libx265: add user data unregistered SEI encoding

MISB ST 0604 and ST 2101 require user data unregistered SEI messages
(precision timestamps and sensor identifiers) to be included. That
currently isn't supported for libx265. This patch adds support
for user data unregistered SEI messages in accordance with
ISO/IEC 23008-2:2020 Section D.2.7

The design is based on nvenc, with support finished up at
57de80673c

Signed-off-by: Derek Buitenhuis <derek.buitenhuis@gmail.com>

libavcodec/libx265.c

@@ -35,6 +35,7 @@
 #include "encode.h"
 #include "internal.h"
 #include "packet_internal.h"
+#include "sei.h"
 
 typedef struct libx265Context {
     const AVClass *class;
@@ -51,6 +52,9 @@ typedef struct libx265Context {
     char *profile;
     AVDictionary *x265_opts;
 
+    void *sei_data;
+    int sei_data_size;
+
     /**
      * If the encoder does not support ROI then warn the first time we
      * encounter a frame with ROI side data.
@@ -78,6 +82,7 @@ static av_cold int libx265_encode_close(AVCodecContext *avctx)
     libx265Context *ctx = avctx->priv_data;
 
     ctx->api->param_free(ctx->params);
+    av_freep(&ctx->sei_data);
 
     if (ctx->encoder)
         ctx->api->encoder_close(ctx->encoder);
@@ -489,6 +494,8 @@ static int libx265_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
     ctx->api->picture_init(ctx->params, &x265pic);
 
     if (pic) {
+        x265_sei *sei = &x265pic.userSEI;
+        sei->numPayloads = 0;
         for (i = 0; i < 3; i++) {
            x265pic.planes[i] = pic->data[i];
            x265pic.stride[i] = pic->linesize[i];
@@ -516,6 +523,32 @@ static int libx265_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
 
             memcpy(x265pic.userData, &pic->reordered_opaque, sizeof(pic->reordered_opaque));
         }
+
+        for (i = 0; i < pic->nb_side_data; i++) {
+            AVFrameSideData *side_data = pic->side_data[i];
+            void *tmp;
+            x265_sei_payload *sei_payload;
+
+            if (side_data->type != AV_FRAME_DATA_SEI_UNREGISTERED)
+                continue;
+
+            tmp = av_fast_realloc(ctx->sei_data,
+                                  &ctx->sei_data_size,
+                                  (sei->numPayloads + 1) * sizeof(*sei_payload));
+            if (!tmp) {
+                av_freep(&x265pic.userData);
+                av_freep(&x265pic.quantOffsets);
+                return AVERROR(ENOMEM);
+            }
+            ctx->sei_data = tmp;
+            sei->payloads = ctx->sei_data;
+            sei_payload = &sei->payloads[sei->numPayloads];
+            sei_payload->payload = side_data->data;
+            sei_payload->payloadSize = side_data->size;
+            /* Equal to libx265 USER_DATA_UNREGISTERED */
+            sei_payload->payloadType = SEI_TYPE_USER_DATA_UNREGISTERED;
+            sei->numPayloads++;
+        }
     }
 
     ret = ctx->api->encoder_encode(ctx->encoder, &nal, &nnal,