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avfilter/vf_v360: add ball projection format

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This commit is contained in:
Paul B Mahol 2019-09-19 18:36:19 +02:00
parent b766a13dba
commit b632ad81c5
3 changed files with 92 additions and 0 deletions
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3
doc/filters.texi
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@ -18060,6 +18060,9 @@ If diagonal field of view is set it overrides horizontal and vertical field of v
@item mercator
Mercator format.
@item ball
Ball format, gives significant distortion toward the back.
@end table
@item interp

1
libavfilter/v360.h
View File

@ -40,6 +40,7 @@ enum Projections {
CUBEMAP_1_6,
STEREOGRAPHIC,
MERCATOR,
BALL,
NB_PROJECTIONS,
};

88
libavfilter/vf_v360.c
View File

@ -66,6 +66,7 @@ static const AVOption v360_options[] = {
{ "c1x6", "cubemap 1x6", 0, AV_OPT_TYPE_CONST, {.i64=CUBEMAP_1_6}, 0, 0, FLAGS, "in" },
{ "sg", "stereographic", 0, AV_OPT_TYPE_CONST, {.i64=STEREOGRAPHIC}, 0, 0, FLAGS, "in" },
{ "mercator", "mercator", 0, AV_OPT_TYPE_CONST, {.i64=MERCATOR}, 0, 0, FLAGS, "in" },
{ "ball", "ball", 0, AV_OPT_TYPE_CONST, {.i64=BALL}, 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" },
@ -81,6 +82,7 @@ static const AVOption v360_options[] = {
{ "c1x6", "cubemap 1x6", 0, AV_OPT_TYPE_CONST, {.i64=CUBEMAP_1_6}, 0, 0, FLAGS, "out" },
{ "sg", "stereographic", 0, AV_OPT_TYPE_CONST, {.i64=STEREOGRAPHIC}, 0, 0, FLAGS, "out" },
{ "mercator", "mercator", 0, AV_OPT_TYPE_CONST, {.i64=MERCATOR}, 0, 0, FLAGS, "out" },
{ "ball", "ball", 0, AV_OPT_TYPE_CONST, {.i64=BALL}, 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" },
@ -1582,6 +1584,80 @@ static void mercator_to_xyz(const V360Context *s,
vec[2] = -cos_theta * cos_phi;
}
/**
* Calculate frame position in ball format for corresponding 3D coordinates on sphere.
*
* @param s filter 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 void xyz_to_ball(const V360Context *s,
const float *vec, int width, int height,
uint16_t us[4][4], uint16_t vs[4][4], float *du, float *dv)
{
const float l = hypotf(vec[0], vec[1]);
const float r = sinf(acosf(-vec[2]) * 0.5f);
float uf, vf;
int ui, vi;
uf = (1.f - r * vec[0] / l) * width / 2.f;
vf = (1.f + r * vec[1] / l) * height / 2.f;
ui = floorf(uf);
vi = floorf(vf);
*du = uf - ui;
*dv = vf - vi;
for (int i = -1; i < 3; i++) {
for (int j = -1; j < 3; j++) {
us[i + 1][j + 1] = mod(ui + j, width);
vs[i + 1][j + 1] = av_clip(vi + i, 0, height - 1);
}
}
}
/**
* Calculate 3D coordinates on sphere for corresponding frame position in ball format.
*
* @param s filter 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 void ball_to_xyz(const V360Context *s,
int i, int j, int width, int height,
float *vec)
{
const float x = (2.f * i) / width - 1.f;
const float y = (2.f * j) / height - 1.f;
const float l = hypotf(x, y);
if (l <= 1.f) {
const float phi = atan2f(x, y);
const float theta = 2.f * asinf(l);
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] = sin_theta * sin_phi;
vec[1] = -sin_theta * cos_phi;
vec[2] = -cos_theta;
} else {
vec[0] = 0.f;
vec[1] = -1.f;
vec[2] = 0.f;
}
}
/**
* Prepare data for processing equi-angular cubemap input format.
*
@ -2429,6 +2505,12 @@ static int config_output(AVFilterLink *outlink)
wf = w;
hf = h;
break;
case BALL:
s->in_transform = xyz_to_ball;
err = 0;
wf = w;
hf = h / 2.f;
break;
default:
av_log(ctx, AV_LOG_ERROR, "Specified input format is not handled.\n");
return AVERROR_BUG;
@ -2499,6 +2581,12 @@ static int config_output(AVFilterLink *outlink)
w = roundf(wf);
h = roundf(hf);
break;
case BALL:
s->out_transform = ball_to_xyz;
prepare_out = NULL;
w = roundf(wf);
h = roundf(hf * 2.f);
break;
default:
av_log(ctx, AV_LOG_ERROR, "Specified output format is not handled.\n");
return AVERROR_BUG;