[vlc-devel] [PATCH 4/6] video_output: conditionnally render on display

[Alexandre Janniaux]

Hi,

As I've mentioned in the commit message, since the disabling
of rendering needs to grab display lock, and prepare/display
is protected behind display lock, it's either bother prepare
and display are called with the same picture or none of them
are called.

Regards,
--
Alexandre Janniaux
Videolabs

On Fri, Feb 05, 2021 at 10:20:25AM +0100, Thomas Guillem wrote:
>
>
> On Fri, Feb 5, 2021, at 10:01, Alexandre Janniaux wrote:
> > Don't prepare/display if rendering is disabled. Rendering can only be
> > disabled when taking the display_lock so the prepare/display cannot be
> > done partially because of this patch.
> > ---
> >  src/video_output/video_output.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/src/video_output/video_output.c
> > b/src/video_output/video_output.c
> > index d225e56d8d..11c50871c1 100644
> > --- a/src/video_output/video_output.c
> > +++ b/src/video_output/video_output.c
> > @@ -1405,7 +1405,7 @@ static int
> > ThreadDisplayRenderPicture(vout_thread_sys_t *vout, bool render_now)
> >      const unsigned frame_rate = todisplay->format.i_frame_rate;
> >      const unsigned frame_rate_base =
> > todisplay->format.i_frame_rate_base;
> >
> > -    if (vd->ops->prepare != NULL)
> > +    if (vd->ops->prepare != NULL && sys->rendering_enabled)
> >          vd->ops->prepare(vd, todisplay, do_dr_spu ? subpic : NULL, system_pts);
> >
> >      vout_chrono_Stop(&sys->render);
> > @@ -1452,7 +1452,9 @@ static int
> > ThreadDisplayRenderPicture(vout_thread_sys_t *vout, bool render_now)
> >                            frame_rate, frame_rate_base);
> >
> >      /* Display the direct buffer returned by vout_RenderPicture */
> > -    vout_display_Display(vd, todisplay);
> > +    if (sys->rendering_enabled)
> > +        vout_display_Display(vd, todisplay);
>
> cf. prepare documentation:
>      * If prepare is not \c NULL, there is an implicit guarantee that display
>      * will be invoked with the exact same picture afterwards:
>
> If the prepare callback is called, then the display should always be called after. Indeed, some modules allocates resources on prepare() and release them on display().
>
> > +
> >      vlc_mutex_unlock(&sys->display_lock);
> >
> >      if (subpic)
> > --
> > 2.28.0
> >
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