I prefer first patch, as it makes the code simpler and starting at 0 simplifies all arithmetic operations, but it makes a slight behaviour change, so I also propose the second version. Note how the 1-indexed logic makes the documentation for "on" awkward.
Regards, -- Nicolas George
From e6bce546af4041bd09eca9a0e66aa1c33426bd3e Mon Sep 17 00:00:00 2001
From: Nicolas George <geo...@nsup.org>
Date: Mon, 1 Dec 2014 16:16:07 +0100
Subject: [PATCH] lavfi/zoompan: fix frame count logic.
Signed-off-by: Nicolas George <geo...@nsup.org>
---
doc/filters.texi | 4 ++--
libavfilter/vf_zoompan.c | 6 +++---
2 files changed, 5 insertions(+), 5 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 8c16c7a..6d52966 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -9307,10 +9307,10 @@ Output width.
Output height.
@item in
-Input frame count.
+Input frame count, starting at 0.
@item on
-Output frame count.
+Output frame count, starting at 0.
@item x
@item y
diff --git a/libavfilter/vf_zoompan.c b/libavfilter/vf_zoompan.c
index 8f179e6..f55095f 100644
--- a/libavfilter/vf_zoompan.c
+++ b/libavfilter/vf_zoompan.c
@@ -134,8 +134,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
var_values[VAR_IN_H] = var_values[VAR_IH] = in->height;
var_values[VAR_OUT_W] = var_values[VAR_OW] = s->w;
var_values[VAR_OUT_H] = var_values[VAR_OH] = s->h;
- var_values[VAR_IN] = inlink->frame_count + 1;
- var_values[VAR_ON] = outlink->frame_count + 1;
+ var_values[VAR_IN] = inlink->frame_count;
+ var_values[VAR_ON] = outlink->frame_count;
var_values[VAR_PX] = s->x;
var_values[VAR_PY] = s->y;
var_values[VAR_X] = 0;
@@ -165,7 +165,7 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *in)
var_values[VAR_TIME] = pts * av_q2d(outlink->time_base);
var_values[VAR_FRAME] = i;
- var_values[VAR_ON] = outlink->frame_count + 1;
+ var_values[VAR_ON] = outlink->frame_count;
if ((ret = av_expr_parse_and_eval(&zoom, s->zoom_expr_str,
var_names, var_values,
NULL, NULL, NULL, NULL, NULL, 0, ctx)) < 0)
--
2.1.3
From ff4c5488bdc167100af791cf9e232494c0b5b7f1 Mon Sep 17 00:00:00 2001
From: Nicolas George <geo...@nsup.org>
Date: Mon, 1 Dec 2014 16:16:07 +0100
Subject: [PATCH] lavfi/zoompan: clarify documentation about frame counts.
Signed-off-by: Nicolas George <geo...@nsup.org>
---
doc/filters.texi | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/doc/filters.texi b/doc/filters.texi
index 8c16c7a..84bf671 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -9307,10 +9307,12 @@ Output width.
Output height.
@item in
-Input frame count.
+Input frame count, including the current one.
@item on
-Output frame count.
+Output frame count, including the current one except. For the @var{d}
+expression, this the frame count associated to the first output frame, even
+if the final result is 0.
@item x
@item y
--
2.1.3
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