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[FFmpeg-devel,V3,2/3] libavfilter/buffersink.c: unref private_ref when frame leaves libavfilter

Message ID 20210222073045.16070-2-yejun.guo@intel.com
State Superseded
Headers show
Series [FFmpeg-devel,V3,1/3] libavfilter/bbox.h: add BoundingBoxHeader and BoundingBox
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Commit Message

Guo, Yejun Feb. 22, 2021, 7:30 a.m. UTC
---
 libavfilter/buffersink.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Nicolas George Feb. 22, 2021, 4:05 p.m. UTC | #1
Guo, Yejun (12021-02-22):
> ---
>  libavfilter/buffersink.c | 1 +
>  1 file changed, 1 insertion(+)

This does not seem correct: the ref count is not raised by buffersink,
it probably should not lower it.

What circumstances are you trying to fix exactly?

Regards,
Guo, Yejun Feb. 23, 2021, 12:49 a.m. UTC | #2
> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of Nicolas
> George
> Sent: 2021年2月23日 0:05
> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> Cc: Guo, Yejun <yejun.guo@intel.com>
> Subject: Re: [FFmpeg-devel] [PATCH V3 2/3] libavfilter/buffersink.c: unref
> private_ref when frame leaves libavfilter
> 
> Guo, Yejun (12021-02-22):
> > ---
> >  libavfilter/buffersink.c | 1 +
> >  1 file changed, 1 insertion(+)
> 
> This does not seem correct: the ref count is not raised by buffersink, it
> probably should not lower it.
> 
> What circumstances are you trying to fix exactly?

The purpose is to support filter object detection. We need a place within AVFrame
to save bounding boxes (the result of object detection, where are the objects, and
what are the objects). And we plan to use AVFrame->private_ref as now, see more discussion
at http://ffmpeg.org/pipermail/ffmpeg-devel/2021-February/276641.html

As at https://github.com/FFmpeg/FFmpeg/blob/master/libavutil/frame.h#L683, 
private_ref is for internal use by a single libav* library. 
It has to be NULL when ownership of the frame leaves the respective library, 

buffersink is the last step when the frame leaves libavfilter, so I add unref here.

In the patch 3 of this patch set, private_ref is allocated in filter vf_dnn_detect.c to save
the detected bounding boxes.

Other filters such as classify, bbox_to_roi (both in plan) will need the bounding boxes, and
we also plan to update vf_drawbox/text to visualize the bounding boxes. 

> 
> Regards,
> 
> --
>   Nicolas George
diff mbox series

Patch

diff --git a/libavfilter/buffersink.c b/libavfilter/buffersink.c
index 58848941d4..837a6e9e82 100644
--- a/libavfilter/buffersink.c
+++ b/libavfilter/buffersink.c
@@ -98,6 +98,7 @@  static int return_or_keep_frame(BufferSinkContext *buf, AVFrame *out, AVFrame *i
     } else {
         av_assert1(out);
         buf->peeked_frame = NULL;
+        av_buffer_unref(&in->private_ref);
         av_frame_move_ref(out, in);
         av_frame_free(&in);
         return 0;