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fosphor: Review the GL frequency mapping and switch zoom to {center,span} 

Previously we were hiding the extrema bin, now we display it "half" on
each side which sort of maps better to the concept of circular spectrum

At the same time we move the zoom spec to {center,span} rather than
{start,stop} since it makes more sense and matches the channel specs

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
This commit is contained in:
Sylvain Munaut 2020-01-31 10:21:53 +01:00
parent e8a64b7297
commit 09b31b4acf
4 changed files with 37 additions and 44 deletions
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4
lib/fosphor/fosphor.c
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@ -191,8 +191,8 @@ fosphor_render_defaults(struct fosphor_render *render)
render->histo_wf_ratio = 0.5f;
render->freq_n_div = 10;
render->freq_start = 0.0f;
render->freq_stop = 1.0f;
render->freq_center = 0.5f;
render->freq_span = 1.0f;
render->wf_span = 1.0f;
}

6
lib/fosphor/fosphor.h
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@ -82,9 +82,9 @@ struct fosphor_render
int options; /*!< \brief Options (See FRO_??? constants) */
float histo_wf_ratio; /*!< \brief Ratio histogram/waterfall ]0,1[ */
int freq_n_div; /*!< \brief Number of frequency divisions */
float freq_start; /*!< \brief Frequency zoom start [0,1[ */
float freq_stop; /*!< \brief Frequency zoom stop ]0,1] */
float wf_span; /*!< \brief Waterfall time zoom ]0,1] */
float freq_center; /*!< \brief Frequency zoom center ]0,1[ */
float freq_span; /*!< \brief Frequency zoom span ]0,1] */
float wf_span; /*!< \brief Waterfall time zoom ]0,1] */
/*! \brief Displayed channels */
struct fosphor_channel channels[FOSPHOR_MAX_CHANNELS];

62
lib/fosphor/gl.c
View File

@ -368,31 +368,30 @@ fosphor_gl_draw(struct fosphor *self, struct fosphor_render *render)
struct fosphor_gl_state *gl = self->gl;
struct freq_axis freq_axis;
float x[2], y[2], u[2], v[2];
float tw, bw;
float tw;
int i;
/* Utils */
tw = 1.0f / (float)FOSPHOR_FFT_LEN; /* Texel width */
bw = 1.0f / (float)(FOSPHOR_FFT_LEN-1); /* Bin width (displayed) */
tw = 1.0f / (float)(FOSPHOR_FFT_LEN); /* Texel width */
/* Texture mapping notes:
*
* - The texture have the "DC" bin at texel 0, however we want it to
* be displayed centered and to do so, texture coordinates are used.
* - One of the bin is not displayed (the one at u=0.5f) because
* it is neither positive freq, nor negative ones, but both. To
* compensate for this, the (1.0f - tw) factor is used.
* - The center of the extrema bin (which is neither positive or
* negative) is mapped to the border of the texture.
*
* Vertex mapping notes:
*
* - We want the vertex to appear at the center of the displayed bins
* - The vertex 'X' coordinates are filled in by the display kernel as
* ((bin #) ^ (N >> 1)) / (N >> 1) - 1
* - So the DC bin is 0.0f and the undisplayed bin is -1. The others
* are spread between [ -1+2*tw to 1-2*tw ]
* - So the DC bin is 0.0 and the undisplayed bin is -1.0. The others
* are spread between [ -1.0 + (tw/2.0) to 1.0 - (tw/2.0) ]
* - For display, that range is first remapped to [0 to 1], then to
* [ bw/2 to 1-bw/2 ] (where bw is normalized displayed bin width)
* so that each point maps to the center of the bin on the textures.
* [ tw to 1-tw ] (we skip 1 tw on each side. One half tw because of
* the half not displayed extrema bin, and another half to center
* inside the first displayed bin on each side)
* - Finally the zoom is applied and then the transform to map on the
* requested screen area
*/
@ -406,8 +405,8 @@ fosphor_gl_draw(struct fosphor *self, struct fosphor_render *render)
y[0] = render->_y_wf[0];
y[1] = render->_y_wf[1];
u[0] = 0.5f + tw + ((1.0f - tw) * render->freq_start);
u[1] = 0.5f + tw + ((1.0f - tw) * render->freq_stop);
u[0] = 0.5f + (tw / 2.0f) + render->freq_center - (render->freq_span / 2.0f);
u[1] = 0.5f + (tw / 2.0f) + render->freq_center + (render->freq_span / 2.0f);
v[1] = (float)render->_wf_pos / 1024.0f;
v[0] = v[1] - render->wf_span;
@ -440,8 +439,8 @@ fosphor_gl_draw(struct fosphor *self, struct fosphor_render *render)
y[0] = render->_y_histo[0];
y[1] = render->_y_histo[1];
u[0] = 0.5f + tw + ((1.0f - tw) * render->freq_start);
u[1] = 0.5f + tw + ((1.0f - tw) * render->freq_stop);
u[0] = 0.5f + (tw / 2.0f) + render->freq_center - (render->freq_span / 2.0f);
u[1] = 0.5f + (tw / 2.0f) + render->freq_center + (render->freq_span / 2.0f);
v[0] = 0.0f;
v[1] = 1.0f;
@ -487,8 +486,14 @@ fosphor_gl_draw(struct fosphor *self, struct fosphor_render *render)
int idx[2], len;
/* Select end-points */
idx[0] = 1 + (int)ceilf (render->freq_start * (float)(FOSPHOR_FFT_LEN - 1) - 0.5f);
idx[1] = 1 + (int)floorf(render->freq_stop * (float)(FOSPHOR_FFT_LEN - 1) - 0.5f);
idx[0] = ceilf ((float)(FOSPHOR_FFT_LEN) * (render->freq_center - (render->freq_span / 2.0f)));
idx[1] = floorf((float)(FOSPHOR_FFT_LEN) * (render->freq_center + (render->freq_span / 2.0f)));
if (idx[0] < 1)
idx[0] = 1;
if (idx[1] >= FOSPHOR_FFT_LEN)
idx[1] = FOSPHOR_FFT_LEN - 1;
len = idx[1] - idx[0] + 1;
/* Setup */
@ -512,12 +517,12 @@ fosphor_gl_draw(struct fosphor *self, struct fosphor_render *render)
glTranslatef(0.0f, self->power.offset, 0.0f);
/* Spectrum range selection */
glScalef(1.0f / (render->freq_stop - render->freq_start), 1.0f, 1.0f);
glTranslatef(-render->freq_start, 0.0f, 0.0f);
glScalef(1.0f / render->freq_span, 1.0f, 1.0f);
glTranslatef(- render->freq_center + render->freq_span / 2.0f, 0.0f, 0.0f);
/* Map the center of each N-1 bins */
glTranslatef(0.5f * bw, 0.0f, 0.0f);
glScalef(1.0f - bw, 1.0f, 1.0f);
glTranslatef(tw, 0.0f, 0.0f);
glScalef(1.0f - 2.0 * tw, 1.0f, 1.0f);
/* Spectrum x scaling to [0.0 -> 1.0] range */
glTranslatef(0.5f, 0.0f, 0.0f);
@ -559,21 +564,14 @@ fosphor_gl_draw(struct fosphor *self, struct fosphor_render *render)
}
/* Setup frequency axis */
if (render->freq_start != 0.0f || render->freq_stop != 1.0f)
if (render->freq_center != 0.5f || render->freq_span != 1.0f)
{
/* The freq_{start,stop} have some imprecisions due to the floating
* point nature. To avoid this crapping the display of the axis, we
* try to 'round' them */
double freq_start = round(1e7 * render->freq_start) / 1e7;
double freq_stop = round(1e7 * render->freq_stop) / 1e7;
double rel_center = ((freq_stop + freq_start) / 2.0) - 0.5;
double rel_span = (freq_stop - freq_start);
double view_center = self->frequency.center + self->frequency.span * (double)(render->freq_center - 0.5f);
double view_span = self->frequency.span * (double)render->freq_span;
freq_axis_build(&freq_axis,
self->frequency.center + rel_center * self->frequency.span,
self->frequency.span * rel_span,
view_center,
view_span,
render->freq_n_div
);
}

9
lib/fosphor/main.c
View File

@ -195,8 +195,6 @@ glfw_render(GLFWwindow *wnd)
static void
_update_fosphor(void)
{
float f;
/* Configure the screen zones */
if (g_as->zoom_enable)
{
@ -231,11 +229,8 @@ _update_fosphor(void)
g_as->render_main.channels[0].center = (float)g_as->zoom_center;
g_as->render_main.channels[0].width = (float)g_as->zoom_width;
f = (float)(g_as->zoom_center - g_as->zoom_width / 2.0);
g_as->render_zoom.freq_start = f > 0.0f ? (f < 1.0f ? f : 1.0f) : 0.0f;
f = (float)(g_as->zoom_center + g_as->zoom_width / 2.0);
g_as->render_zoom.freq_stop = f > 0.0f ? (f < 1.0f ? f : 1.0f) : 0.0f;
g_as->render_zoom.freq_center = g_as->zoom_center;
g_as->render_zoom.freq_span = g_as->zoom_width;
/* Update render options */
fosphor_render_refresh(&g_as->render_main);