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

[James Almer]

On 9/28/2021 6:22 PM, Soft Works wrote:
> 
> 
>> -----Original Message-----
>> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of
>> James Almer
>> Sent: Tuesday, 28 September 2021 23:19
>> 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 6:00 PM, Soft Works wrote:
>>>
>>>
>>>> -----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.
>>
>> Ok, but i insist you should use ff_inlink_make_frame_writable(). If
>> it
>> wont use the vflip custom get_buffer.video function, it will instead
>> use
>> the default allocator, which makes use of a lavfi frame pool.
> 
> I've gone through very single video filter's filter_frame function
> and I've seen not a single one making use of it.

That'd be because it's called automatically for filters that set 
AVFILTERPAD_FLAG_NEEDS_WRITABLE. Since these don't, you should do it 
manually.

> 
> That might be a task for a different day, I suppose...?

Why? You're adding av_frame_make_writable() calls. I'm asking you to 
instead make them ff_inlink_make_frame_writable() calls.

> 
> softworkz
> 
> 
> 
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