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Introduce di_cvt_compute()
Same as di_gtf_compute(), but for CVT. Code imported from edid-decode, fixed up [1] [2], edited for code style and extended to return all output parameters. Will help with CVT timing code descriptors in EDID [3]. [1]: https://lore.kernel.org/linux-media/20221005121221.14882-1-contact@emersion.fr/T/#u [2]: https://lore.kernel.org/linux-media/20221028142405.81894-1-contact@emersion.fr/T/#u [3]: https://gitlab.freedesktop.org/emersion/libdisplay-info/-/merge_requests/93 Signed-off-by: Simon Ser <contact@emersion.fr>
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Simon Ser
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155
cvt.c
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155
cvt.c
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/*
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* Copyright 2006-2012 Red Hat, Inc.
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* Copyright 2018-2021 Cisco Systems, Inc. and/or its affiliates. All rights reserved.
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*
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* Originally imported from edid-decode.
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*/
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#include <math.h>
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#include <libdisplay-info/cvt.h>
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/**
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* The size of the top and bottom overscan margin as a percentage of the active
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* vertical image.
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*/
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#define MARGIN_PERC 1.8
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#define MIN_VSYNC_BP 550.0
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#define MIN_V_PORCH 3
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/**
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* Minimum vertical backporch for CVT and CVT RBv1.
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*/
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#define MIN_V_BPORCH 7
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/**
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* Fixed vertical backporch for CVT RBv2 and RBv3.
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*/
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#define FIXED_V_BPORCH 6
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#define C_PRIME 30.0
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#define M_PRIME 300.0
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/**
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* Minimum VBlank period (in µs) for RB timings.
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*/
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#define RB_MIN_VBLANK 460.0
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void
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di_cvt_compute(struct di_cvt_timing *t, const struct di_cvt_options *options)
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{
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enum di_cvt_reduced_blanking_version rb = options->red_blank_ver;
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double cell_gran, h_pixels_rnd, v_lines_rnd, hor_margin, vert_margin,
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interlace, total_active_pixels, v_field_rate_rqd, clock_step,
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h_blank, rb_v_fporch, refresh_multiplier, rb_min_vblank, h_sync,
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v_sync, pixel_freq, v_blank, v_sync_bp, additional_hblank,
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h_period_est, ideal_duty_cycle, total_pixels, vbi_lines,
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rb_v_bporch, rb_min_vbi, total_v_lines, freq, h_front_porch,
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v_back_porch, act_h_freq;
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cell_gran = rb == DI_CVT_REDUCED_BLANKING_V2 ? 1 : 8;
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h_pixels_rnd = floor(options->h_pixels / cell_gran) * cell_gran;
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v_lines_rnd = options->int_rqd ? floor(options->v_lines / 2.0) : options->v_lines;
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hor_margin = options->margins_rqd
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? floor((h_pixels_rnd * MARGIN_PERC / 100.0) / cell_gran) * cell_gran
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: 0;
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vert_margin = options->margins_rqd
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? floor(MARGIN_PERC / 100.0 * v_lines_rnd)
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: 0;
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interlace = options->int_rqd ? 0.5 : 0;
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total_active_pixels = h_pixels_rnd + hor_margin * 2;
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v_field_rate_rqd = options->int_rqd
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? options->ip_freq_rqd * 2
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: options->ip_freq_rqd;
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clock_step = rb >= DI_CVT_REDUCED_BLANKING_V2 ? 0.001 : 0.25;
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h_blank = rb == DI_CVT_REDUCED_BLANKING_V1 ? 160 : 80;
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rb_v_fporch = rb == DI_CVT_REDUCED_BLANKING_V1 ? 3 : 1;
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refresh_multiplier = (rb == DI_CVT_REDUCED_BLANKING_V2 && options->video_opt) ? 1000.0 / 1001.0 : 1;
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rb_min_vblank = rb == DI_CVT_REDUCED_BLANKING_V3 ? options->vblank : RB_MIN_VBLANK;
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if (rb_min_vblank < RB_MIN_VBLANK)
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rb_min_vblank = RB_MIN_VBLANK;
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h_sync = 32;
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if (rb == DI_CVT_REDUCED_BLANKING_V3) {
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additional_hblank = options->additional_hblank;
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if (additional_hblank < 0)
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additional_hblank = 0;
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else if (additional_hblank > 120)
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additional_hblank = 120;
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h_blank += additional_hblank;
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}
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/* Determine VSync Width from aspect ratio */
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if ((options->v_lines * 4 / 3) == options->h_pixels)
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v_sync = 4;
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else if ((options->v_lines * 16 / 9) == options->h_pixels)
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v_sync = 5;
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else if ((options->v_lines * 16 / 10) == options->h_pixels)
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v_sync = 6;
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else if (!(options->v_lines % 4) && ((options->v_lines * 5 / 4) == options->h_pixels))
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v_sync = 7;
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else if ((options->v_lines * 15 / 9) == options->h_pixels)
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v_sync = 7;
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else /* Custom */
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v_sync = 10;
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if (rb >= DI_CVT_REDUCED_BLANKING_V2)
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v_sync = 8;
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if (rb == DI_CVT_REDUCED_BLANKING_NONE) {
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h_period_est = (1.0 / v_field_rate_rqd - MIN_VSYNC_BP / 1000000.0) /
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(v_lines_rnd + vert_margin * 2 + MIN_V_PORCH + interlace) * 1000000.0;
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v_sync_bp = floor(MIN_VSYNC_BP / h_period_est) + 1;
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if (v_sync_bp < v_sync + MIN_V_BPORCH)
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v_sync_bp = v_sync + MIN_V_BPORCH;
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v_blank = v_sync_bp + MIN_V_PORCH;
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total_v_lines = v_lines_rnd + vert_margin * 2 + v_sync_bp +
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interlace + MIN_V_PORCH;
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ideal_duty_cycle = C_PRIME - M_PRIME * h_period_est / 1000.0;
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if (ideal_duty_cycle < 20)
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ideal_duty_cycle = 20;
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h_blank = floor(total_active_pixels * ideal_duty_cycle /
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(100.0 - ideal_duty_cycle) /
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(2 * cell_gran)) * 2 * cell_gran;
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total_pixels = total_active_pixels + h_blank;
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h_sync = floor(total_pixels * 0.08 / cell_gran) * cell_gran;
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pixel_freq = floor(total_pixels / h_period_est / clock_step) * clock_step;
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} else {
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h_period_est = (1000000.0 / v_field_rate_rqd - rb_min_vblank) /
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(v_lines_rnd + vert_margin * 2);
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vbi_lines = floor(rb_min_vblank / h_period_est) + 1;
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rb_v_bporch = rb == DI_CVT_REDUCED_BLANKING_V1 ? MIN_V_BPORCH : FIXED_V_BPORCH;
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rb_min_vbi = rb_v_fporch + v_sync + rb_v_bporch;
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v_blank = vbi_lines < rb_min_vbi ? rb_min_vbi : vbi_lines;
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total_v_lines = v_blank + v_lines_rnd + vert_margin * 2 + interlace;
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if (rb == DI_CVT_REDUCED_BLANKING_V3 && options->early_vsync_rqd)
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rb_v_bporch = floor(vbi_lines / 2.0);
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if (rb == DI_CVT_REDUCED_BLANKING_V1)
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v_sync_bp = v_blank - rb_v_fporch;
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else
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v_sync_bp = v_sync + rb_v_bporch;
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total_pixels = h_blank + total_active_pixels;
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freq = v_field_rate_rqd * total_v_lines * total_pixels * refresh_multiplier;
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if (rb == DI_CVT_REDUCED_BLANKING_V3)
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pixel_freq = ceil(freq / 1000000.0 / clock_step) * clock_step;
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else
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pixel_freq = floor(freq / 1000000.0 / clock_step) * clock_step;
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}
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if (rb >= DI_CVT_REDUCED_BLANKING_V2)
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h_front_porch = 8;
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else
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h_front_porch = (h_blank / 2.0) - h_sync;
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v_back_porch = v_sync_bp - v_sync;
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act_h_freq = 1000 * pixel_freq / total_pixels;
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*t = (struct di_cvt_timing){
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.act_pixel_freq = pixel_freq,
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.total_active_pixels = total_active_pixels,
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.v_lines_rnd = v_lines_rnd,
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.h_front_porch = h_front_porch,
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.h_sync = h_sync,
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.h_back_porch = h_blank - h_front_porch - h_sync,
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.v_front_porch = v_blank - v_back_porch - v_sync,
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.v_back_porch = v_back_porch,
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.v_sync = v_sync,
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.act_frame_rate = 1000 * act_h_freq / total_v_lines,
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};
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}
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76
include/libdisplay-info/cvt.h
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76
include/libdisplay-info/cvt.h
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#ifndef DI_CVT_H
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#define DI_CVT_H
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/**
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* Low-level API for VESA Coordinated Video Timings (CVT) version 2.0.
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*/
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#include <stdbool.h>
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#include <stdint.h>
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enum di_cvt_reduced_blanking_version {
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DI_CVT_REDUCED_BLANKING_NONE,
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DI_CVT_REDUCED_BLANKING_V1,
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DI_CVT_REDUCED_BLANKING_V2,
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DI_CVT_REDUCED_BLANKING_V3,
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};
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/**
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* Input parameters, defined in table 3-1.
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*/
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struct di_cvt_options {
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/* Version of the reduced blanking timing formula to be used */
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enum di_cvt_reduced_blanking_version red_blank_ver;
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/* Desired active (visible) horizontal pixels and vertical lines per
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* frame */
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int32_t h_pixels, v_lines;
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/* Target vertical refresh rate (in Hz) */
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double ip_freq_rqd;
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/* Whether to generate a "video-optimized" timing variant (RBv2 only) */
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bool video_opt;
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/* Desired VBlank time (in µs, RBv3 only, must be greater than 460) */
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double vblank;
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/* Desired additional number of pixels to add to the base HBlank
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* duration (RBv3 only, must be a multiple of 8 between 0 and 120) */
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int32_t additional_hblank;
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/* Indicates whether the VSync location is early (RBv3 only) */
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bool early_vsync_rqd;
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/* Whether interlaced is required (no RB and RBv1 only) */
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bool int_rqd;
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/* Whether margins are required (no RB and RBv1 only) */
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bool margins_rqd;
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};
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/**
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* Output parameters, defined in table 3-4.
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*/
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struct di_cvt_timing {
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/* Pixel clock frequency (in MHz) */
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double act_pixel_freq;
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/* Total number of active (visible) pixels per line */
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double total_active_pixels;
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/* Total number of active (visible) vertical lines per frame */
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double v_lines_rnd;
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/* Number of pixels in the horizontal front porch period */
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double h_front_porch;
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/* Number of pixels in the HSync period */
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double h_sync;
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/* Number of pixels in the horizontal back porch period */
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double h_back_porch;
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/* Number of lines in the vertical front porch period */
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double v_front_porch;
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/* Number of lines in the VSync period */
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double v_sync;
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/* Number of lines in the vertical back porch period */
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double v_back_porch;
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/* Frame rate (in Hz) */
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double act_frame_rate;
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};
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/**
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* Compute a timing via the CVT formula.
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*/
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void
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di_cvt_compute(struct di_cvt_timing *t, const struct di_cvt_options *options);
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#endif
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@ -51,6 +51,7 @@ di_lib = library(
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'display-info',
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[
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'cta.c',
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'cvt.c',
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'displayid.c',
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'dmt-table.c',
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'edid.c',
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