[Mesa-dev] [PATCH] st/va: Fix forward/backward referencing for deinterlacing

[Mark Thompson]

The VAAPI documentation is not very clear here, but the intent
appears to be that a forward reference is forward from a frame in the
past, not forward to a frame in the future (that is, forward as in
forward prediction, not as in a forward reference in source code).
This interpretation is derived from other implementations, in
particular the i965 driver and the gstreamer client.

In order to match those other implementations, this patch swaps the
meaning of forward and backward references as they currently appear
for motion-adaptive deinterlacing.

Signed-off-by: Mark Thompson <sw at jkqxz.net>
---
 src/gallium/state_trackers/va/postproc.c | 10 +++++-----
 src/gallium/state_trackers/va/surface.c  |  4 ++--
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/gallium/state_trackers/va/postproc.c b/src/gallium/state_trackers/va/postproc.c
index 01e240f016..fbec69aec3 100644
--- a/src/gallium/state_trackers/va/postproc.c
+++ b/src/gallium/state_trackers/va/postproc.c
@@ -184,13 +184,13 @@ vlVaApplyDeint(vlVaDriver *drv, vlVaContext *context,
 {
    vlVaSurface *prevprev, *prev, *next;
 
-   if (param->num_forward_references < 1 ||
-       param->num_backward_references < 2)
+   if (param->num_forward_references < 2 ||
+       param->num_backward_references < 1)
       return current;
 
-   prevprev = handle_table_get(drv->htab, param->backward_references[1]);
-   prev = handle_table_get(drv->htab, param->backward_references[0]);
-   next = handle_table_get(drv->htab, param->forward_references[0]);
+   prevprev = handle_table_get(drv->htab, param->forward_references[1]);
+   prev = handle_table_get(drv->htab, param->forward_references[0]);
+   next = handle_table_get(drv->htab, param->backward_references[0]);
 
    if (!prevprev || !prev || !next)
       return current;
diff --git a/src/gallium/state_trackers/va/surface.c b/src/gallium/state_trackers/va/surface.c
index 0e1dbe0b10..b129e6c74f 100644
--- a/src/gallium/state_trackers/va/surface.c
+++ b/src/gallium/state_trackers/va/surface.c
@@ -845,8 +845,8 @@ vlVaQueryVideoProcPipelineCaps(VADriverContextP ctx, VAContextID context,
       case VAProcFilterDeinterlacing: {
          VAProcFilterParameterBufferDeinterlacing *deint = buf->data;
          if (deint->algorithm == VAProcDeinterlacingMotionAdaptive) {
-            pipeline_cap->num_forward_references = 1;
-            pipeline_cap->num_backward_references = 2;
+            pipeline_cap->num_forward_references = 2;
+            pipeline_cap->num_backward_references = 1;
          }
          break;
       }
-- 
2.11.0