[FFmpeg-devel] [PATCH 2/7] decode: add a method for attaching lavc-internal data to frames

[wm4]

From: Anton Khirnov <anton at khirnov.net>

Use the AVFrame.opaque_ref field. The original user's opaque_ref is
wrapped in the lavc struct and then unwrapped before the frame is
returned to the caller.

This new struct will be useful in the following commits.

Merges Libav commit 359a8a3e2d1194b52b6c386f94fd0929567dfb67.
---
 libavcodec/decode.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 libavcodec/decode.h | 13 ++++++++++++
 2 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/libavcodec/decode.c b/libavcodec/decode.c
index 437b848248..04f7156154 100644
--- a/libavcodec/decode.c
+++ b/libavcodec/decode.c
@@ -640,6 +640,26 @@ static int decode_receive_frame_internal(AVCodecContext *avctx, AVFrame *frame)
     if (ret == AVERROR_EOF)
         avci->draining_done = 1;
 
+    /* unwrap the per-frame decode data and restore the original opaque_ref*/
+    if (!ret) {
+        /* the only case where decode data is not set should be decoders
+         * that do not call ff_get_buffer() */
+        av_assert0((frame->opaque_ref && frame->opaque_ref->size == sizeof(FrameDecodeData)) ||
+                   !(avctx->codec->capabilities & AV_CODEC_CAP_DR1));
+
+        if (frame->opaque_ref) {
+            FrameDecodeData *fdd;
+            AVBufferRef *user_opaque_ref;
+
+            fdd = (FrameDecodeData*)frame->opaque_ref->data;
+
+            user_opaque_ref = fdd->user_opaque_ref;
+            fdd->user_opaque_ref = NULL;
+            av_buffer_unref(&frame->opaque_ref);
+            frame->opaque_ref = user_opaque_ref;
+        }
+    }
+
     return ret;
 }
 
@@ -1612,6 +1632,37 @@ static void validate_avframe_allocation(AVCodecContext *avctx, AVFrame *frame)
     }
 }
 
+static void decode_data_free(void *opaque, uint8_t *data)
+{
+    FrameDecodeData *fdd = (FrameDecodeData*)data;
+
+    av_buffer_unref(&fdd->user_opaque_ref);
+
+    av_freep(&fdd);
+}
+
+static int attach_decode_data(AVFrame *frame)
+{
+    AVBufferRef *fdd_buf;
+    FrameDecodeData *fdd;
+
+    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);
+    }
+
+    fdd->user_opaque_ref = frame->opaque_ref;
+    frame->opaque_ref    = fdd_buf;
+
+    return 0;
+}
+
 static int get_buffer_internal(AVCodecContext *avctx, AVFrame *frame, int flags)
 {
     const AVHWAccel *hwaccel = avctx->hwaccel;
@@ -1648,8 +1699,14 @@ 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)
-        validate_avframe_allocation(avctx, frame);
+    if (ret < 0)
+        goto end;
+
+    validate_avframe_allocation(avctx, frame);
+
+    ret = attach_decode_data(frame);
+    if (ret < 0)
+        goto end;
 
 end:
     if (avctx->codec_type == AVMEDIA_TYPE_VIDEO && !override_dimensions &&
diff --git a/libavcodec/decode.h b/libavcodec/decode.h
index c9630228dc..ab8327f95c 100644
--- a/libavcodec/decode.h
+++ b/libavcodec/decode.h
@@ -21,8 +21,21 @@
 #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
+ * opaque_ref.
+ */
+typedef struct FrameDecodeData {
+    /**
+     * The original user-set opaque_ref.
+     */
+    AVBufferRef *user_opaque_ref;
+} FrameDecodeData;
+
 /**
  * Called by decoders to get the next packet for decoding.
  *
-- 
2.14.1