[FFmpeg-cvslog] avfilter/vf_v360: add cylindrical equal area format
Paul B Mahol
git at videolan.org
Wed Jun 30 01:16:09 EEST 2021
ffmpeg | branch: master | Paul B Mahol <onemda at gmail.com> | Wed Jun 30 00:12:41 2021 +0200| [e11fd47f8df2631db9da14b22d34e3c390d91ba8] | committer: Paul B Mahol
avfilter/vf_v360: add cylindrical equal area format
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=e11fd47f8df2631db9da14b22d34e3c390d91ba8
---
doc/filters.texi | 4 ++
libavfilter/v360.h | 1 +
libavfilter/vf_v360.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 129 insertions(+)
diff --git a/doc/filters.texi b/doc/filters.texi
index 67ad228d8b..13236965ce 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -20977,6 +20977,10 @@ If diagonal field of view is set it overrides horizontal and vertical field of v
Octahedron projection.
@end table
+ at item cylindricalea
+Cylindrical Equal Area projection.
+ at end table
+
@item interp
Set interpolation method.@*
@i{Note: more complex interpolation methods require much more memory to run.}
diff --git a/libavfilter/v360.h b/libavfilter/v360.h
index 87770664a3..b8ade2591c 100644
--- a/libavfilter/v360.h
+++ b/libavfilter/v360.h
@@ -54,6 +54,7 @@ enum Projections {
EQUISOLID,
ORTHOGRAPHIC,
OCTAHEDRON,
+ CYLINDRICALEA,
NB_PROJECTIONS,
};
diff --git a/libavfilter/vf_v360.c b/libavfilter/vf_v360.c
index c47a4015e8..0c47883d4d 100644
--- a/libavfilter/vf_v360.c
+++ b/libavfilter/vf_v360.c
@@ -84,6 +84,7 @@ static const AVOption v360_options[] = {
{ "equisolid", "equisolid", 0, AV_OPT_TYPE_CONST, {.i64=EQUISOLID}, 0, 0, FLAGS, "in" },
{ "og", "orthographic", 0, AV_OPT_TYPE_CONST, {.i64=ORTHOGRAPHIC}, 0, 0, FLAGS, "in" },
{"octahedron", "octahedron", 0, AV_OPT_TYPE_CONST, {.i64=OCTAHEDRON}, 0, 0, FLAGS, "in" },
+ {"cylindricalea", "cylindrical equal area", 0, AV_OPT_TYPE_CONST, {.i64=CYLINDRICALEA}, 0, 0, FLAGS, "in" },
{ "output", "set output projection", OFFSET(out), AV_OPT_TYPE_INT, {.i64=CUBEMAP_3_2}, 0, NB_PROJECTIONS-1, FLAGS, "out" },
{ "e", "equirectangular", 0, AV_OPT_TYPE_CONST, {.i64=EQUIRECTANGULAR}, 0, 0, FLAGS, "out" },
{ "equirect", "equirectangular", 0, AV_OPT_TYPE_CONST, {.i64=EQUIRECTANGULAR}, 0, 0, FLAGS, "out" },
@@ -114,6 +115,7 @@ static const AVOption v360_options[] = {
{ "equisolid", "equisolid", 0, AV_OPT_TYPE_CONST, {.i64=EQUISOLID}, 0, 0, FLAGS, "out" },
{ "og", "orthographic", 0, AV_OPT_TYPE_CONST, {.i64=ORTHOGRAPHIC}, 0, 0, FLAGS, "out" },
{"octahedron", "octahedron", 0, AV_OPT_TYPE_CONST, {.i64=OCTAHEDRON}, 0, 0, FLAGS, "out" },
+ {"cylindricalea", "cylindrical equal area", 0, AV_OPT_TYPE_CONST, {.i64=CYLINDRICALEA}, 0, 0, FLAGS, "out" },
{ "interp", "set interpolation method", OFFSET(interp), AV_OPT_TYPE_INT, {.i64=BILINEAR}, 0, NB_INTERP_METHODS-1, FLAGS, "interp" },
{ "near", "nearest neighbour", 0, AV_OPT_TYPE_CONST, {.i64=NEAREST}, 0, 0, FLAGS, "interp" },
{ "nearest", "nearest neighbour", 0, AV_OPT_TYPE_CONST, {.i64=NEAREST}, 0, 0, FLAGS, "interp" },
@@ -3136,6 +3138,116 @@ static int xyz_to_cylindrical(const V360Context *s,
return visible;
}
+/**
+ * Prepare data for processing cylindrical equal area output format.
+ *
+ * @param ctx filter context
+ *
+ * @return error code
+ */
+static int prepare_cylindricalea_out(AVFilterContext *ctx)
+{
+ V360Context *s = ctx->priv;
+
+ s->flat_range[0] = s->h_fov * M_PI / 360.f;
+ s->flat_range[1] = s->v_fov / 180.f;
+
+ return 0;
+}
+
+/**
+ * Prepare data for processing cylindrical equal area input format.
+ *
+ * @param ctx filter context
+ *
+ * @return error code
+ */
+static int prepare_cylindricalea_in(AVFilterContext *ctx)
+{
+ V360Context *s = ctx->priv;
+
+ s->iflat_range[0] = M_PI * s->ih_fov / 360.f;
+ s->iflat_range[1] = s->iv_fov / 180.f;
+
+ return 0;
+}
+
+/**
+ * Calculate 3D coordinates on sphere for corresponding frame position in cylindrical equal area format.
+ *
+ * @param s filter private context
+ * @param i horizontal position on frame [0, width)
+ * @param j vertical position on frame [0, height)
+ * @param width frame width
+ * @param height frame height
+ * @param vec coordinates on sphere
+ */
+static int cylindricalea_to_xyz(const V360Context *s,
+ int i, int j, int width, int height,
+ float *vec)
+{
+ const float uf = s->flat_range[0] * ((2.f * i + 1.f) / width - 1.f);
+ const float vf = s->flat_range[1] * ((2.f * j + 1.f) / height - 1.f);
+
+ const float phi = uf;
+ const float theta = asinf(vf);
+
+ const float sin_phi = sinf(phi);
+ const float cos_phi = cosf(phi);
+ const float sin_theta = sinf(theta);
+ const float cos_theta = cosf(theta);
+
+ vec[0] = cos_theta * sin_phi;
+ vec[1] = sin_theta;
+ vec[2] = cos_theta * cos_phi;
+
+ normalize_vector(vec);
+
+ return 1;
+}
+
+/**
+ * Calculate frame position in cylindrical equal area format for corresponding 3D coordinates on sphere.
+ *
+ * @param s filter private context
+ * @param vec coordinates on sphere
+ * @param width frame width
+ * @param height frame height
+ * @param us horizontal coordinates for interpolation window
+ * @param vs vertical coordinates for interpolation window
+ * @param du horizontal relative coordinate
+ * @param dv vertical relative coordinate
+ */
+static int xyz_to_cylindricalea(const V360Context *s,
+ const float *vec, int width, int height,
+ int16_t us[4][4], int16_t vs[4][4], float *du, float *dv)
+{
+ const float phi = atan2f(vec[0], vec[2]) / s->iflat_range[0];
+ const float theta = asinf(vec[1]);
+
+ const float uf = (phi + 1.f) * (width - 1) / 2.f;
+ const float vf = (sinf(theta) / s->iflat_range[1] + 1.f) * height / 2.f;
+
+ const int ui = floorf(uf);
+ const int vi = floorf(vf);
+
+ const int visible = vi >= 0 && vi < height && ui >= 0 && ui < width &&
+ theta <= M_PI * s->iv_fov / 180.f &&
+ theta >= -M_PI * s->iv_fov / 180.f;
+
+ *du = uf - ui;
+ *dv = vf - vi;
+
+ for (int i = 0; i < 4; i++) {
+ for (int j = 0; j < 4; j++) {
+ us[i][j] = visible ? av_clip(ui + j - 1, 0, width - 1) : 0;
+ vs[i][j] = visible ? av_clip(vi + i - 1, 0, height - 1) : 0;
+ }
+ }
+
+ return visible;
+}
+
/**
* Calculate 3D coordinates on sphere for corresponding frame position in perspective format.
*
@@ -4448,6 +4560,12 @@ static int config_output(AVFilterLink *outlink)
wf = w;
hf = h * 2.f;
break;
+ case CYLINDRICALEA:
+ s->in_transform = xyz_to_cylindricalea;
+ err = prepare_cylindricalea_in(ctx);
+ wf = w;
+ hf = h;
+ break;
case TETRAHEDRON:
s->in_transform = xyz_to_tetrahedron;
err = 0;
@@ -4596,6 +4714,12 @@ static int config_output(AVFilterLink *outlink)
w = lrintf(wf);
h = lrintf(hf * 0.5f);
break;
+ case CYLINDRICALEA:
+ s->out_transform = cylindricalea_to_xyz;
+ prepare_out = prepare_cylindricalea_out;
+ w = lrintf(wf);
+ h = lrintf(hf);
+ break;
case PERSPECTIVE:
s->out_transform = perspective_to_xyz;
prepare_out = NULL;
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