decode: add a method for attaching lavc-internal data to frames

Use the AVFrame.private_ref field.

This new struct will be useful in the following commits.

Merges Libav commit 359a8a3e2d.

libavcodec/decode.c

@@ -613,6 +613,16 @@ static int decode_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
     if (ret == AVERROR_EOF)
         avci->draining_done = 1;
 
+    /* free the per-frame decode data */
+    if (!ret) {
+        /* the only case where decode data is not set should be decoders
+         * that do not call ff_get_buffer() */
+        av_assert0((frame->private_ref && frame->private_ref->size == sizeof(FrameDecodeData)) ||
+                   !(avctx->codec->capabilities & AV_CODEC_CAP_DR1));
+
+        av_buffer_unref(&frame->private_ref);
+    }
+
     return ret;
 }
 
@@ -1552,6 +1562,37 @@ static void validate_avframe_allocation(AVCodecContext *avctx, AVFrame *frame)
     }
 }
 
+static void decode_data_free(void *opaque, uint8_t *data)
+{
+    FrameDecodeData *fdd = (FrameDecodeData*)data;
+
+    av_freep(&fdd);
+}
+
+int ff_attach_decode_data(AVFrame *frame)
+{
+    AVBufferRef *fdd_buf;
+    FrameDecodeData *fdd;
+
+    av_assert1(!frame->private_ref);
+    av_buffer_unref(&frame->private_ref);
+
+    fdd = av_mallocz(sizeof(*fdd));
+    if (!fdd)
+        return AVERROR(ENOMEM);
+
+    fdd_buf = av_buffer_create((uint8_t*)fdd, sizeof(*fdd), decode_data_free,
+                               NULL, AV_BUFFER_FLAG_READONLY);
+    if (!fdd_buf) {
+        av_freep(&fdd);
+        return AVERROR(ENOMEM);
+    }
+
+    frame->private_ref = fdd_buf;
+
+    return 0;
+}
+
 static int get_buffer_internal(AVCodecContext *avctx, AVFrame *frame, int flags)
 {
     const AVHWAccel *hwaccel = avctx->hwaccel;
@@ -1588,9 +1629,15 @@ static int get_buffer_internal(AVCodecContext *avctx, AVFrame *frame, int flags)
         avctx->sw_pix_fmt = avctx->pix_fmt;
 
     ret = avctx->get_buffer2(avctx, frame, flags);
-    if (ret >= 0)
+    if (ret < 0)
+        goto end;
+
     validate_avframe_allocation(avctx, frame);
 
+    ret = ff_attach_decode_data(frame);
+    if (ret < 0)
+        goto end;
+
 end:
     if (avctx->codec_type == AVMEDIA_TYPE_VIDEO && !override_dimensions &&
         !(avctx->codec->caps_internal & FF_CODEC_CAP_EXPORTS_CROPPING)) {

libavcodec/decode.h

@@ -21,8 +21,17 @@
 #ifndef AVCODEC_DECODE_H
 #define AVCODEC_DECODE_H
 
+#include "libavutil/buffer.h"
+
 #include "avcodec.h"
 
+/**
+ * This struct stores per-frame lavc-internal data and is attached to it via
+ * private_ref.
+ */
+typedef struct FrameDecodeData {
+} FrameDecodeData;
+
 /**
  * Called by decoders to get the next packet for decoding.
  *
@@ -36,4 +45,6 @@ int ff_decode_get_packet(AVCodecContext *avctx, AVPacket *pkt);
 
 void ff_decode_bsfs_uninit(AVCodecContext *avctx);
 
+int ff_attach_decode_data(AVFrame *frame);
+
 #endif /* AVCODEC_DECODE_H */

libavcodec/wrapped_avframe.c

@@ -25,6 +25,7 @@
  */
 
 #include "avcodec.h"
+#include "decode.h"
 #include "internal.h"
 
 #include "libavutil/internal.h"
@@ -98,6 +99,12 @@ static int wrapped_avframe_decode(AVCodecContext *avctx, void *data,
 
     av_frame_move_ref(out, in);
 
+    err = ff_attach_decode_data(out);
+    if (err < 0) {
+        av_frame_unref(out);
+        return err;
+    }
+
     *got_frame = 1;
     return 0;
 }