[FFmpeg-devel] [PATCH v2 1/1] avfilter/frames: Ensure frames are writable when processing in-place

[Soft Works]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
> James Almer
> Sent: Tuesday, 28 September 2021 22:08
> To: ffmpeg-devel at ffmpeg.org
> Subject: Re: [FFmpeg-devel] [PATCH v2 1/1] avfilter/frames: Ensure
> frames are writable when processing in-place
> 
> On 9/28/2021 4:54 PM, Soft Works wrote:
> > Signed-off-by: softworkz <softworkz at hotmail.com>
> > ---
> > v2: Reduced to cases without AVFILTERPAD_FLAG_NEEDS_WRITABLE
> 
> Can't this flag used in these filters?

Not in vf_vflip, because in case of flip_bayer, it's using a
custom allocation (.get_buffer.video)

> >   libavfilter/vf_cover_rect.c | 7 +++++--
> >   libavfilter/vf_floodfill.c  | 5 +++++
> >   libavfilter/vf_vflip.c      | 7 ++++++-
> >   3 files changed, 16 insertions(+), 3 deletions(-)
> >
> > diff --git a/libavfilter/vf_cover_rect.c
> b/libavfilter/vf_cover_rect.c
> > index 0a8c10e06d..2367afb4b3 100644
> > --- a/libavfilter/vf_cover_rect.c
> > +++ b/libavfilter/vf_cover_rect.c
> > @@ -136,7 +136,7 @@ static int filter_frame(AVFilterLink *inlink,
> AVFrame *in)
> >       AVFilterContext *ctx = inlink->dst;
> >       CoverContext *cover = ctx->priv;
> >       AVDictionaryEntry *ex, *ey, *ew, *eh;
> > -    int x = -1, y = -1, w = -1, h = -1;
> > +    int x = -1, y = -1, w = -1, h = -1, ret;
> >       char *xendptr = NULL, *yendptr = NULL, *wendptr = NULL,
> *hendptr = NULL;
> >
> >       ex = av_dict_get(in->metadata, "lavfi.rect.x", NULL,
> AV_DICT_MATCH_CASE);
> > @@ -181,7 +181,10 @@ static int filter_frame(AVFilterLink *inlink,
> AVFrame *in)
> >       x = av_clip(x, 0, in->width  - w);
> >       y = av_clip(y, 0, in->height - h);
> >
> > -    av_frame_make_writable(in);
> > +    if ((ret = av_frame_make_writable(in)) < 0) {
> > +        av_frame_free(&in);
> > +        return ret;
> > +    }
> >
> >       if (cover->mode == MODE_BLUR) {
> >           blur (cover, in, x, y);
> > diff --git a/libavfilter/vf_floodfill.c
> b/libavfilter/vf_floodfill.c
> > index 21741cdb4f..292b27505e 100644
> > --- a/libavfilter/vf_floodfill.c
> > +++ b/libavfilter/vf_floodfill.c
> > @@ -294,6 +294,11 @@ static int filter_frame(AVFilterLink *link,
> AVFrame *frame)
> >       const int h = frame->height;
> >       int i, ret;
> >
> > +    if ((ret = av_frame_make_writable(frame)) < 0) {
> > +        av_frame_free(&frame);
> > +        return ret;
> > +    }
> > +
> >       if (is_inside(s->x, s->y, w, h)) {
> >           s->pick_pixel(frame, s->x, s->y, &s0, &s1, &s2, &s3);
> >
> > diff --git a/libavfilter/vf_vflip.c b/libavfilter/vf_vflip.c
> > index 0d624512f9..622bd46db3 100644
> > --- a/libavfilter/vf_vflip.c
> > +++ b/libavfilter/vf_vflip.c
> > @@ -108,11 +108,16 @@ static int flip_bayer(AVFilterLink *link,
> AVFrame *in)
> >   static int filter_frame(AVFilterLink *link, AVFrame *frame)
> >   {
> >       FlipContext *flip = link->dst->priv;
> > -    int i;
> > +    int i, ret;
> >
> >       if (flip->bayer)
> >           return flip_bayer(link, frame);
> >
> > +    if ((ret = av_frame_make_writable(frame)) < 0) {
> 
> vf_vflip defines a custom get_buffer.video() function, so you can't
> use
> av_frame_make_writable() as the buffer it will return in case it
> needs
> to allocate a writable one may not be suitable. You need to use
> ff_inlink_make_frame_writable() instead, and in all three filters
> while
> at it.

.get_buffer.video is used for the case of flip_bayer, but not otherwise.
Otherwise it was currently writing to the incoming frame directly, 
and that's what this patch fixes.

softworkz