[FFmpeg-devel] [PATCH 5/6] pngdec: fix and simplify apng reference handling

[Anton Khirnov]

Quoting Paul B Mahol (2021-02-17 11:52:31)
> On Tue, Feb 16, 2021 at 9:26 PM Anton Khirnov <anton at khirnov.net> wrote:
> > @@ -1088,23 +1084,23 @@ static int handle_p_frame_apng(AVCodecContext
> > *avctx, PNGDecContext *s,
> >      if (!buffer)
> >          return AVERROR(ENOMEM);
> >
> > +    ff_thread_await_progress(&s->last_picture, INT_MAX, 0);
> >
> > -    // Do the disposal operation specified by the last frame on the frame
> > -    if (s->last_dispose_op != APNG_DISPOSE_OP_PREVIOUS) {
> > -        ff_thread_await_progress(&s->last_picture, INT_MAX, 0);
> > -        memcpy(buffer, s->last_picture.f->data[0], s->image_linesize *
> > s->height);
> > -
> > -        if (s->last_dispose_op == APNG_DISPOSE_OP_BACKGROUND)
> > -            for (y = s->last_y_offset; y < s->last_y_offset + s->last_h;
> > ++y)
> > -                memset(buffer + s->image_linesize * y + s->bpp *
> > s->last_x_offset, 0, s->bpp * s->last_w);
> > +    // need to reset a rectangle to background:
> > +    // create a new writable copy
> > +    if (s->last_dispose_op == APNG_DISPOSE_OP_BACKGROUND) {
> > +        int ret = av_frame_make_writable(s->last_picture.f);
> > +        if (ret < 0)
> > +            return ret;
> >
> > -        memcpy(s->previous_picture.f->data[0], buffer, s->image_linesize
> > * s->height);
> > -        ff_thread_report_progress(&s->previous_picture, INT_MAX, 0);
> > -    } else {
> > -        ff_thread_await_progress(&s->previous_picture, INT_MAX, 0);
> > -        memcpy(buffer, s->previous_picture.f->data[0], s->image_linesize
> > * s->height);
> > +        for (y = s->last_y_offset; y < s->last_y_offset + s->last_h; y++)
> > {
> > +            memset(s->last_picture.f->data[0] + s->image_linesize * y +
> > +                   s->bpp * s->last_x_offset, 0, s->bpp * s->last_w);
> > +        }
> >      }
> >
> > +    memcpy(buffer, s->last_picture.f->data[0], s->image_linesize *
> > s->height);
> > +
> >      // Perform blending
> >      if (s->blend_op == APNG_BLEND_OP_SOURCE) {
> >          for (y = s->y_offset; y < s->y_offset + s->cur_h; ++y) {
> > @@ -1448,22 +1444,17 @@ exit_loop:
> >              if (CONFIG_PNG_DECODER && avctx->codec_id != AV_CODEC_ID_APNG)
> >                  handle_p_frame_png(s, p);
> >              else if (CONFIG_APNG_DECODER &&
> > -                     s->previous_picture.f->width == p->width  &&
> > -                     s->previous_picture.f->height== p->height &&
> > -                     s->previous_picture.f->format== p->format &&
> >
> 
> No explanation provided why those line are removed.
>

They are removed because previous_picture is removed. As is actually
explained in the commit message.

-- 
Anton Khirnov