[FFmpeg-devel] [PATCH] avfilter/vf_libplacebo: implement rotation option

* [FFmpeg-devel] [PATCH] avfilter/vf_libplacebo: implement rotation option
@ 2025-05-16 11:07 Niklas Haas
  2025-05-21 13:09 ` Niklas Haas
  0 siblings, 1 reply; 2+ messages in thread
From: Niklas Haas @ 2025-05-16 11:07 UTC (permalink / raw)
  To: ffmpeg-devel; +Cc: Niklas Haas

From: Niklas Haas <git@haasn.dev>

Flipping can already be accomplished by setting the crop_w/h expressions to
their negative values, so together these options can implement any of the
common frame orientations.
---
 doc/filters.texi            | 10 ++++++++++
 libavfilter/avfilter.c      |  3 ++-
 libavfilter/vf_libplacebo.c | 23 +++++++++++++++++++++++
 3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/doc/filters.texi b/doc/filters.texi
index 679b71f290..434fdec109 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -16259,6 +16259,16 @@ and @code{(oh-ph)/2}.
 Set the output placement width/height expressions, default values are @code{ow}
 and @code{oh}.
 
+@item rotate
+Rotate the input frame clockwise by the specified angle.
+
+@table @samp
+@item 0, 360
+@item 90
+@item 180
+@item 270
+@end table
+
 @item fps
 Set the output frame rate. This can be rational, e.g. @code{60000/1001}. If
 set to the special string @code{none} (the default), input timestamps will
diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
index 64c1075c40..f113b6a186 100644
--- a/libavfilter/avfilter.c
+++ b/libavfilter/avfilter.c
@@ -1062,7 +1062,8 @@ int ff_filter_frame(AVFilterLink *link, AVFrame *frame)
             strcmp(link->dst->filter->name, "format") &&
             strcmp(link->dst->filter->name, "idet") &&
             strcmp(link->dst->filter->name, "null") &&
-            strcmp(link->dst->filter->name, "scale")) {
+            strcmp(link->dst->filter->name, "scale") &&
+            strcmp(link->dst->filter->name, "libplacebo")) {
             av_assert1(frame->format        == link->format);
             av_assert1(frame->width         == link->w);
             av_assert1(frame->height        == link->h);
diff --git a/libavfilter/vf_libplacebo.c b/libavfilter/vf_libplacebo.c
index 86e1f43dea..7accf8ead9 100644
--- a/libavfilter/vf_libplacebo.c
+++ b/libavfilter/vf_libplacebo.c
@@ -193,6 +193,7 @@ typedef struct LibplaceboContext {
     int color_range;
     int color_primaries;
     int color_trc;
+    int rotation;
     AVDictionary *extra_opts;
 
     int have_hwdevice;
@@ -802,6 +803,13 @@ static void update_crops(AVFilterContext *ctx, LibplaceboInput *in,
         image->crop.y0 = av_expr_eval(s->crop_y_pexpr, s->var_values, NULL);
         image->crop.x1 = image->crop.x0 + s->var_values[VAR_CROP_W];
         image->crop.y1 = image->crop.y0 + s->var_values[VAR_CROP_H];
+        image->rotation = s->rotation;
+        if (s->rotation % PL_ROTATION_180 == PL_ROTATION_90) {
+            /* Libplacebo expects the input crop relative to the actual frame
+             * dimensions, so un-transpose them here */
+            FFSWAP(float, image->crop.x0, image->crop.y0);
+            FFSWAP(float, image->crop.x1, image->crop.y1);
+        }
 
         if (src == ref) {
             /* Only update the target crop once, for the 'reference' frame */
@@ -1198,6 +1206,14 @@ static int libplacebo_config_input(AVFilterLink *inlink)
     AVFilterContext *avctx = inlink->dst;
     LibplaceboContext *s   = avctx->priv;
 
+    if (s->rotation % PL_ROTATION_180 == PL_ROTATION_90) {
+        /* Swap width and height for 90 degree rotations to make the size and
+         * scaling calculations work out correctly */
+        FFSWAP(int, inlink->w, inlink->h);
+        if (inlink->sample_aspect_ratio.num)
+            inlink->sample_aspect_ratio = av_inv_q(inlink->sample_aspect_ratio);
+    }
+
     if (inlink->format == AV_PIX_FMT_VULKAN)
         return ff_vk_filter_config_input(inlink);
 
@@ -1386,6 +1402,13 @@ static const AVOption libplacebo_options[] = {
     {"smpte2084",                      NULL,  0, AV_OPT_TYPE_CONST, {.i64=AVCOL_TRC_SMPTE2084},    INT_MIN, INT_MAX, STATIC, .unit = "color_trc"},
     {"arib-std-b67",                   NULL,  0, AV_OPT_TYPE_CONST, {.i64=AVCOL_TRC_ARIB_STD_B67}, INT_MIN, INT_MAX, STATIC, .unit = "color_trc"},
 
+    {"rotate", "rotate the input clockwise", OFFSET(rotation), AV_OPT_TYPE_INT, {.i64=PL_ROTATION_0}, PL_ROTATION_0, PL_ROTATION_360, DYNAMIC, .unit = "rotation"},
+    {"0",                              NULL,  0, AV_OPT_TYPE_CONST, {.i64=PL_ROTATION_0},   .flags = STATIC, .unit = "rotation"},
+    {"90",                             NULL,  0, AV_OPT_TYPE_CONST, {.i64=PL_ROTATION_90},  .flags = STATIC, .unit = "rotation"},
+    {"180",                            NULL,  0, AV_OPT_TYPE_CONST, {.i64=PL_ROTATION_180}, .flags = STATIC, .unit = "rotation"},
+    {"270",                            NULL,  0, AV_OPT_TYPE_CONST, {.i64=PL_ROTATION_270}, .flags = STATIC, .unit = "rotation"},
+    {"360",                            NULL,  0, AV_OPT_TYPE_CONST, {.i64=PL_ROTATION_360}, .flags = STATIC, .unit = "rotation"},
+
     { "upscaler", "Upscaler function", OFFSET(upscaler), AV_OPT_TYPE_STRING, {.str = "spline36"}, .flags = DYNAMIC },
     { "downscaler", "Downscaler function", OFFSET(downscaler), AV_OPT_TYPE_STRING, {.str = "mitchell"}, .flags = DYNAMIC },
     { "frame_mixer", "Frame mixing function", OFFSET(frame_mixer), AV_OPT_TYPE_STRING, {.str = "none"}, .flags = DYNAMIC },
-- 
2.49.0

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