vf_hwupload/hwmap: Support setting a fixed pool size

These filters do not directly know whether the API they are using will
support dynamic frame pools, so this is somewhat tricky.  If the user
sets extra_hw_frames, we assume that they are aware of the problem and
set a fixed size based on that.  If not, most cases use dynamic sizing
just like they did previously.  The hardware-reverse-mapping case for
hwmap previously had a large fixed size (64) here, primarily as a hack
for QSV use - this is removed and extra_hw_frames will need to be set
for QSV to work since it requires fixed-size pools (as the other cases
do, and which didn't work before).

libavfilter/vf_hwmap.c

@@ -138,7 +138,9 @@ static int hwmap_config_output(AVFilterLink *outlink)
             frames->sw_format = hwfc->sw_format;
             frames->width     = hwfc->width;
             frames->height    = hwfc->height;
-            frames->initial_pool_size = 64;
+
+            if (avctx->extra_hw_frames >= 0)
+                frames->initial_pool_size = 2 + avctx->extra_hw_frames;
 
             err = av_hwframe_ctx_init(ctx->hwframes_ref);
             if (err < 0) {
@@ -218,6 +220,9 @@ static int hwmap_config_output(AVFilterLink *outlink)
         hwfc->width     = inlink->w;
         hwfc->height    = inlink->h;
 
+        if (avctx->extra_hw_frames >= 0)
+            hwfc->initial_pool_size = 2 + avctx->extra_hw_frames;
+
         err = av_hwframe_ctx_init(ctx->hwframes_ref);
         if (err < 0) {
             av_log(avctx, AV_LOG_ERROR, "Failed to create frame "

libavfilter/vf_hwupload.c

@@ -133,6 +133,9 @@ static int hwupload_config_output(AVFilterLink *outlink)
     ctx->hwframes->width     = inlink->w;
     ctx->hwframes->height    = inlink->h;
 
+    if (avctx->extra_hw_frames >= 0)
+        ctx->hwframes->initial_pool_size = 2 + avctx->extra_hw_frames;
+
     err = av_hwframe_ctx_init(ctx->hwframes_ref);
     if (err < 0)
         goto fail;