gain_map.c

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/*
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
 
#include "gain_map.h"
#include "mem.h"
 
static void gain_map_params_default(AVGainMapParams *p)
{
    *p = (AVGainMapParams) {
        .base_hdr_headroom      = { 0, 1 },
        .alternate_hdr_headroom = { 0, 1 },
        .nb_channels = 1,
    };
 
    /* Pre-fill all three channels as a convenience */
    for (int c = 0; c < 3; c++) {
        p->channels[c] = (struct AVGainMapChannel) {
            .gain_map_min       = { 0, 1 },
            .gain_map_max       = { 0, 1 },
            .gamma              = { 1, 1 },
            .base_offset        = { 1, 64 },
            .alternate_offset   = { 1, 64 },
        };
    }
}
 
#define CHECK(cond) do { if (!(cond)) return AVERROR_INVALIDDATA; } while (0)
#define CHECK_SIGNED(q)   CHECK((q).den > 0);
#define CHECK_UNSIGNED(q) CHECK((q).num >= 0 && (q).den > 0);
 
int av_gain_map_params_validate(const AVGainMapParams *p)
{
    CHECK(0 <= p->version && p->version <= AV_ISO21496_VERSION);
    CHECK(p->nb_channels == 1 || p->nb_channels == 3);
    CHECK_UNSIGNED(p->base_hdr_headroom);
    CHECK_UNSIGNED(p->alternate_hdr_headroom);
 
    for (int c = 0; c < p->nb_channels; c++) {
        const struct AVGainMapChannel *const ch = &p->channels[c];
        CHECK_SIGNED(ch->gain_map_min);
        CHECK_SIGNED(ch->gain_map_max);
        CHECK_UNSIGNED(ch->gamma);
        CHECK(ch->gamma.num != 0);
        /**
         * Note: The ISO spec declares these as signed, but a negative value
         * makes no numeric sense and would result in infinities in the
         * middle of the valid signal range; so just constrain them to be
         * unsigned as a safeguard. Note that the Adobe hdrgm spec explicitly
         * requires them to be nonnegative as well, so this avoids an
         * inconsistency.
         */
        CHECK_UNSIGNED(ch->base_offset);
        CHECK_UNSIGNED(ch->alternate_offset);
        CHECK(av_cmp_q(ch->gain_map_min, ch->gain_map_max) <= 0);
    }
 
    return 0;
}
 
int av_gain_map_channels_identical(const AVGainMapParams *p)
{
    static_assert(sizeof(p->channels[0]) == sizeof(int[2]) * 5,
                  "AVGainMapChannel struct is tightly packed");
 
    return !memcmp(&p->channels[0], &p->channels[1], sizeof(p->channels[0])) &&
           !memcmp(&p->channels[0], &p->channels[2], sizeof(p->channels[0]));
}
 
AVGainMapParams *av_gain_map_params_alloc(size_t *size)
{
    AVGainMapParams *p = av_malloc(sizeof(AVGainMapParams));
    if (!p)
        return NULL;
 
    gain_map_params_default(p);
 
    if (size)
        *size = sizeof(*p);
 
    return p;
}
 
AVGainMapParams *av_gain_map_params_create_side_data(AVFrameSideData ***fsd, int *nb_sd)
{
    AVFrameSideData *sd;
    sd = av_frame_side_data_new(fsd, nb_sd, AV_FRAME_DATA_GAIN_MAP_PARAMS,
                                sizeof(AVGainMapParams),
                                AV_FRAME_SIDE_DATA_FLAG_REPLACE);
    if (!sd)
        return NULL;
 
    AVGainMapParams *const p = (AVGainMapParams *) sd->data;
    gain_map_params_default(p);
    return p;
}