[vlc-devel] [PATCH] [RFC] video_output: keep track of the vout modules that can switch stereo modes dynamically

[Steve Lhomme]

The idea is to be able to use something like this to avoid recreating a 
new vout when we know the current one can do the switch just fine:


diff --git a/src/input/decoder.c b/src/input/decoder.c
index 0c7ee686b4..dd11628b3a 100644
--- a/src/input/decoder.c
+++ b/src/input/decoder.c
@@ -445,7 +445,8 @@ static int vout_update_format( decoder_t *p_dec )
       || (int64_t)p_dec->fmt_out.video.i_sar_num * 
p_owner->fmt.video.i_sar_den !=
          (int64_t)p_dec->fmt_out.video.i_sar_den * 
p_owner->fmt.video.i_sar_num ||
          p_dec->fmt_out.video.orientation != 
p_owner->fmt.video.orientation ||
-        p_dec->fmt_out.video.multiview_mode != 
p_owner->fmt.video.multiview_mode )
+       (p_dec->fmt_out.video.multiview_mode != 
p_owner->fmt.video.multiview_mode &&
+         !vout_CanHandleStereoMode(p_owner->p_vout, 
p_dec->fmt_out.video.orientation)) )
      {
          vout_thread_t *p_vout;

@@ -572,7 +573,8 @@ static int vout_update_format( decoder_t *p_dec )
           p_dec->fmt_out.video.lighting.MaxCLL !=
           p_owner->fmt.video.lighting.MaxCLL ||
           p_dec->fmt_out.video.lighting.MaxFALL !=
-         p_owner->fmt.video.lighting.MaxFALL)
+         p_owner->fmt.video.lighting.MaxFALL ||
+         p_dec->fmt_out.video.multiview_mode != 
p_owner->fmt.video.multiview_mode )
      {
          /* the format has changed but we don't need a new vout */
          vlc_mutex_lock( &p_owner->lock );


One of the problem here is that the p_owner->p_vout is not locked. But 
it's already used unlocked in the same if(). And the values are 
"constant" after the vout is created (like everything in display_info).


I'll probably rename this function to CanHandleStereoInput() to avoid 
confusion with the display mode which is a different thing and unrelated 
to the decoder. Although it could theoretically need a vout change which 
is currently not possible with the design we have (the decoder would 
need a restart just because the display changes).


On 14/08/2018 16:59, Steve Lhomme wrote:
> ---
>   include/vlc_vout_display.h       | 1 +
>   src/video_output/display.c       | 1 +
>   src/video_output/video_output.c  | 6 ++++++
>   src/video_output/vout_internal.h | 5 +++++
>   4 files changed, 13 insertions(+)
>
> diff --git a/include/vlc_vout_display.h b/include/vlc_vout_display.h
> index 86eb1bced0..830cbf053f 100644
> --- a/include/vlc_vout_display.h
> +++ b/include/vlc_vout_display.h
> @@ -112,6 +112,7 @@ typedef struct {
>       bool is_slow;                           /* The picture memory has slow read/write */
>       bool has_double_click;                  /* Is double-click generated */
>       bool has_pictures_invalid;              /* Will VOUT_DISPLAY_EVENT_PICTURES_INVALID be used */
> +    int stereo_modes;                       /* bitmask of multiview modes supported dynamically */
>       const vlc_fourcc_t *subpicture_chromas; /* List of supported chromas for subpicture rendering. */
>   } vout_display_info_t;
>   
> diff --git a/src/video_output/display.c b/src/video_output/display.c
> index b0c0fdbb3e..a06b441d7f 100644
> --- a/src/video_output/display.c
> +++ b/src/video_output/display.c
> @@ -93,6 +93,7 @@ static vout_display_t *vout_display_New(vlc_object_t *obj,
>       vd->info.has_double_click = false;
>       vd->info.has_pictures_invalid = false;
>       vd->info.subpicture_chromas = NULL;
> +    vd->info.stereo_modes = (1 << MULTIVIEW_2D);
>   
>       vd->cfg = cfg;
>       vd->pool = NULL;
> diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
> index da8022a8f3..c998f5e453 100644
> --- a/src/video_output/video_output.c
> +++ b/src/video_output/video_output.c
> @@ -498,6 +498,12 @@ int vout_GetSnapshot(vout_thread_t *vout,
>       return VLC_SUCCESS;
>   }
>   
> +bool vout_CanHandleStereoMode(vout_thread_t *vout, video_multiview_mode_t mode)
> +{
> +    vout_display_t *vd = vout->p->display.vd;
> +    return vd && vd->info.stereo_modes & (1<<mode);
> +}
> +
>   void vout_ChangeAspectRatio( vout_thread_t *p_vout,
>                                unsigned int i_num, unsigned int i_den )
>   {
> diff --git a/src/video_output/vout_internal.h b/src/video_output/vout_internal.h
> index 8eaac0dee9..a3f472026a 100644
> --- a/src/video_output/vout_internal.h
> +++ b/src/video_output/vout_internal.h
> @@ -280,6 +280,11 @@ void vout_DisplayTitle( vout_thread_t *p_vout, const char *psz_title );
>    */
>   bool vout_IsEmpty( vout_thread_t *p_vout );
>   
> +/**
> + * Returns true if the vout can switch to the multiview mode dynamically.
> + */
> +bool vout_CanHandleStereoMode(vout_thread_t *, video_multiview_mode_t);
> +
>   void vout_SetSpuHighlight( vout_thread_t *p_vout, const vlc_spu_highlight_t * );
>   
>   #endif
> -- 
> 2.17.0
>
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