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avfilter/vf_v360: add stereographic output projection

This commit is contained in:
Paul B Mahol 2019-09-08 18:17:57 +02:00
parent a13b61b7fd
commit 973051e3bd
2 changed files with 38 additions and 0 deletions
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1
libavfilter/v360.h
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@ -31,6 +31,7 @@ enum Projections {
DUAL_FISHEYE,
BARREL,
CUBEMAP_1_6,
STEREOGRAPHIC,
NB_PROJECTIONS,
};

37
libavfilter/vf_v360.c
View File

@ -74,6 +74,7 @@ static const AVOption v360_options[] = {
{ "barrel", "barrel facebook's 360 format", 0, AV_OPT_TYPE_CONST, {.i64=BARREL}, 0, 0, FLAGS, "out" },
{ "fb", "barrel facebook's 360 format", 0, AV_OPT_TYPE_CONST, {.i64=BARREL}, 0, 0, FLAGS, "out" },
{ "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" },
{ "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" },
@ -1377,6 +1378,36 @@ static void equirect_to_xyz(const V360Context *s,
vec[2] = -cos_theta * cos_phi;
}
/**
* Calculate 3D coordinates on sphere for corresponding frame position in stereographic format.
*
* @param s filter context
* @param i horizontal position on frame [0, height)
* @param j vertical position on frame [0, width)
* @param width frame width
* @param height frame height
* @param vec coordinates on sphere
*/
static void stereographic_to_xyz(const V360Context *s,
int i, int j, int width, int height,
float *vec)
{
const float z = 0.5f * s->h_fov * M_PI / 180.f;
const float x = z * (2.f * i / width - 1.f);
const float y = z * (2.f * j / height - 1.f);
const float xy = x * x + y * y;
float norm;
vec[0] = 2.f * x / (1.f + xy);
vec[1] = (-1.f + xy) / (1.f + xy);
vec[2] = 2.f * y / (1.f + xy);
norm = sqrtf(vec[0] * vec[0] + vec[1] * vec[1] + vec[2] * vec[2]);
vec[0] /= norm;
vec[1] /= norm;
vec[2] /= norm;
}
/**
* Calculate frame position in equirectangular format for corresponding 3D coordinates on sphere.
*
@ -2194,6 +2225,12 @@ static int config_output(AVFilterLink *outlink)
w = roundf(wf / 4.f * 5.f);
h = roundf(hf);
break;
case STEREOGRAPHIC:
out_transform = stereographic_to_xyz;
err = 0;
w = FFMAX(roundf(wf), roundf(hf));
h = w;
break;
default:
av_log(ctx, AV_LOG_ERROR, "Specified output format is not handled.\n");
return AVERROR_BUG;