/*

 * Copyright © 2018-2021, VideoLAN and dav1d authors

 * Copyright © 2018, Two Orioles, LLC

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions are met:

 *

 * 1. Redistributions of source code must retain the above copyright notice, this

 *    list of conditions and the following disclaimer.

 *

 * 2. Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 *

 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR

 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "config.h"

#include <errno.h>

#include <limits.h>

#include <stdio.h>

#include "dav1d/data.h"

#include "common/frame.h"

#include "common/intops.h"

#include "common/validate.h"

#include "src/decode.h"

#include "src/getbits.h"

#include "src/levels.h"

#include "src/log.h"

#include "src/obu.h"

#include "src/ref.h"

#include "src/thread_task.h"

static int check_trailing_bits(GetBits *const gb,

                               const int strict_std_compliance)

{

    const int trailing_one_bit = dav1d_get_bit(gb);

    if (gb->error)

        return DAV1D_ERR(EINVAL);

    if (!strict_std_compliance)

        return 0;

    if (!trailing_one_bit || gb->state)

        return DAV1D_ERR(EINVAL);

    ptrdiff_t size = gb->ptr_end - gb->ptr;

    while (size > 0 && gb->ptr[size - 1] == 0)

        size--;

    if (size)

        return DAV1D_ERR(EINVAL);

    return 0;

}

static NOINLINE int parse_seq_hdr(Dav1dSequenceHeader *const hdr,

                                  GetBits *const gb,

                                  const int strict_std_compliance)

{

#define DEBUG_SEQ_HDR 0

#if DEBUG_SEQ_HDR

    const unsigned init_bit_pos = dav1d_get_bits_pos(gb);

#endif

    memset(hdr, 0, sizeof(*hdr));

    hdr->profile = dav1d_get_bits(gb, 3);

    if (hdr->profile > 2) goto error;

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-profile: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    hdr->still_picture = dav1d_get_bit(gb);

    hdr->reduced_still_picture_header = dav1d_get_bit(gb);

    if (hdr->reduced_still_picture_header && !hdr->still_picture) goto error;

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-stillpicture_flags: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    if (hdr->reduced_still_picture_header) {

        hdr->num_operating_points = 1;

        hdr->operating_points[0].major_level = dav1d_get_bits(gb, 3);

        hdr->operating_points[0].minor_level = dav1d_get_bits(gb, 2);

        hdr->operating_points[0].initial_display_delay = 10;

    } else {

        hdr->timing_info_present = dav1d_get_bit(gb);

        if (hdr->timing_info_present) {

            hdr->num_units_in_tick = dav1d_get_bits(gb, 32);

            hdr->time_scale = dav1d_get_bits(gb, 32);

            if (strict_std_compliance && (!hdr->num_units_in_tick || !hdr->time_scale))

                goto error;

            hdr->equal_picture_interval = dav1d_get_bit(gb);

            if (hdr->equal_picture_interval) {

                const unsigned num_ticks_per_picture = dav1d_get_vlc(gb);

                if (num_ticks_per_picture == UINT32_MAX)

                    goto error;

                hdr->num_ticks_per_picture = num_ticks_per_picture + 1;

            }

            hdr->decoder_model_info_present = dav1d_get_bit(gb);

            if (hdr->decoder_model_info_present) {

                hdr->encoder_decoder_buffer_delay_length = dav1d_get_bits(gb, 5) + 1;

                hdr->num_units_in_decoding_tick = dav1d_get_bits(gb, 32);

                if (strict_std_compliance && !hdr->num_units_in_decoding_tick)

                    goto error;

                hdr->buffer_removal_delay_length = dav1d_get_bits(gb, 5) + 1;

                hdr->frame_presentation_delay_length = dav1d_get_bits(gb, 5) + 1;

            }

        }

#if DEBUG_SEQ_HDR

        printf("SEQHDR: post-timinginfo: off=%u\n",

               dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

        hdr->display_model_info_present = dav1d_get_bit(gb);

        hdr->num_operating_points = dav1d_get_bits(gb, 5) + 1;

        for (int i = 0; i < hdr->num_operating_points; i++) {

            struct Dav1dSequenceHeaderOperatingPoint *const op =

                &hdr->operating_points[i];

            op->idc = dav1d_get_bits(gb, 12);

            if (op->idc && (!(op->idc & 0xff) || !(op->idc & 0xf00)))

                goto error;

            op->major_level = 2 + dav1d_get_bits(gb, 3);

            op->minor_level = dav1d_get_bits(gb, 2);

            if (op->major_level > 3)

                op->tier = dav1d_get_bit(gb);

            if (hdr->decoder_model_info_present) {

                op->decoder_model_param_present = dav1d_get_bit(gb);

                if (op->decoder_model_param_present) {

                    struct Dav1dSequenceHeaderOperatingParameterInfo *const opi =

                        &hdr->operating_parameter_info[i];

                    opi->decoder_buffer_delay =

                        dav1d_get_bits(gb, hdr->encoder_decoder_buffer_delay_length);

                    opi->encoder_buffer_delay =

                        dav1d_get_bits(gb, hdr->encoder_decoder_buffer_delay_length);

                    opi->low_delay_mode = dav1d_get_bit(gb);

                }

            }

            if (hdr->display_model_info_present)

                op->display_model_param_present = dav1d_get_bit(gb);

            op->initial_display_delay =

                op->display_model_param_present ? dav1d_get_bits(gb, 4) + 1 : 10;

        }

#if DEBUG_SEQ_HDR

        printf("SEQHDR: post-operating-points: off=%u\n",

               dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    }

    hdr->width_n_bits = dav1d_get_bits(gb, 4) + 1;

    hdr->height_n_bits = dav1d_get_bits(gb, 4) + 1;

    hdr->max_width = dav1d_get_bits(gb, hdr->width_n_bits) + 1;

    hdr->max_height = dav1d_get_bits(gb, hdr->height_n_bits) + 1;

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-size: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    if (!hdr->reduced_still_picture_header) {

        hdr->frame_id_numbers_present = dav1d_get_bit(gb);

        if (hdr->frame_id_numbers_present) {

            hdr->delta_frame_id_n_bits = dav1d_get_bits(gb, 4) + 2;

            hdr->frame_id_n_bits = dav1d_get_bits(gb, 3) + hdr->delta_frame_id_n_bits + 1;

        }

    }

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-frame-id-numbers-present: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    hdr->sb128 = dav1d_get_bit(gb);

    hdr->filter_intra = dav1d_get_bit(gb);

    hdr->intra_edge_filter = dav1d_get_bit(gb);

    if (hdr->reduced_still_picture_header) {

        hdr->screen_content_tools = DAV1D_ADAPTIVE;

        hdr->force_integer_mv = DAV1D_ADAPTIVE;

    } else {

        hdr->inter_intra = dav1d_get_bit(gb);

        hdr->masked_compound = dav1d_get_bit(gb);

        hdr->warped_motion = dav1d_get_bit(gb);

        hdr->dual_filter = dav1d_get_bit(gb);

        hdr->order_hint = dav1d_get_bit(gb);

        if (hdr->order_hint) {

            hdr->jnt_comp = dav1d_get_bit(gb);

            hdr->ref_frame_mvs = dav1d_get_bit(gb);

        }

        hdr->screen_content_tools = dav1d_get_bit(gb) ? DAV1D_ADAPTIVE : dav1d_get_bit(gb);

    #if DEBUG_SEQ_HDR

        printf("SEQHDR: post-screentools: off=%u\n",

               dav1d_get_bits_pos(gb) - init_bit_pos);

    #endif

        hdr->force_integer_mv = hdr->screen_content_tools ?

                                dav1d_get_bit(gb) ? DAV1D_ADAPTIVE : dav1d_get_bit(gb) : 2;

        if (hdr->order_hint)

            hdr->order_hint_n_bits = dav1d_get_bits(gb, 3) + 1;

    }

    hdr->super_res = dav1d_get_bit(gb);

    hdr->cdef = dav1d_get_bit(gb);

    hdr->restoration = dav1d_get_bit(gb);

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-featurebits: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    hdr->hbd = dav1d_get_bit(gb);

    if (hdr->profile == 2 && hdr->hbd)

        hdr->hbd += dav1d_get_bit(gb);

    if (hdr->profile != 1)

        hdr->monochrome = dav1d_get_bit(gb);

    hdr->color_description_present = dav1d_get_bit(gb);

    if (hdr->color_description_present) {

        hdr->pri = dav1d_get_bits(gb, 8);

        hdr->trc = dav1d_get_bits(gb, 8);

        hdr->mtrx = dav1d_get_bits(gb, 8);

    } else {

        hdr->pri = DAV1D_COLOR_PRI_UNKNOWN;

        hdr->trc = DAV1D_TRC_UNKNOWN;

        hdr->mtrx = DAV1D_MC_UNKNOWN;

    }

    if (hdr->monochrome) {

        hdr->color_range = dav1d_get_bit(gb);

        hdr->layout = DAV1D_PIXEL_LAYOUT_I400;

        hdr->ss_hor = hdr->ss_ver = 1;

        hdr->chr = DAV1D_CHR_UNKNOWN;

    } else if (hdr->pri == DAV1D_COLOR_PRI_BT709 &&

               hdr->trc == DAV1D_TRC_SRGB &&

               hdr->mtrx == DAV1D_MC_IDENTITY)

    {

        hdr->layout = DAV1D_PIXEL_LAYOUT_I444;

        hdr->color_range = 1;

        if (hdr->profile != 1 && !(hdr->profile == 2 && hdr->hbd == 2))

            goto error;

    } else {

        hdr->color_range = dav1d_get_bit(gb);

        switch (hdr->profile) {

        case 0: hdr->layout = DAV1D_PIXEL_LAYOUT_I420;

                hdr->ss_hor = hdr->ss_ver = 1;

                break;

        case 1: hdr->layout = DAV1D_PIXEL_LAYOUT_I444;

                break;

        case 2:

            if (hdr->hbd == 2) {

                hdr->ss_hor = dav1d_get_bit(gb);

                if (hdr->ss_hor)

                    hdr->ss_ver = dav1d_get_bit(gb);

            } else

                hdr->ss_hor = 1;

            hdr->layout = hdr->ss_hor ?

                          hdr->ss_ver ? DAV1D_PIXEL_LAYOUT_I420 :

                                        DAV1D_PIXEL_LAYOUT_I422 :

                                        DAV1D_PIXEL_LAYOUT_I444;

            break;

        }

        hdr->chr = (hdr->ss_hor & hdr->ss_ver) ?

                   dav1d_get_bits(gb, 2) : DAV1D_CHR_UNKNOWN;

    }

    if (strict_std_compliance &&

        hdr->mtrx == DAV1D_MC_IDENTITY && hdr->layout != DAV1D_PIXEL_LAYOUT_I444)

    {

        goto error;

    }

    if (!hdr->monochrome)

        hdr->separate_uv_delta_q = dav1d_get_bit(gb);

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-colorinfo: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    hdr->film_grain_present = dav1d_get_bit(gb);

#if DEBUG_SEQ_HDR

    printf("SEQHDR: post-filmgrain: off=%u\n",

           dav1d_get_bits_pos(gb) - init_bit_pos);

#endif

    // We needn't bother flushing the OBU here: we'll check we didn't

    // overrun in the caller and will then discard gb, so there's no

    // point in setting its position properly.

    return check_trailing_bits(gb, strict_std_compliance);

error:

    return DAV1D_ERR(EINVAL);

}

int dav1d_parse_sequence_header(Dav1dSequenceHeader *const out,

                                const uint8_t *const ptr, const size_t sz)

{

    validate_input_or_ret(out != NULL, DAV1D_ERR(EINVAL));

    validate_input_or_ret(ptr != NULL, DAV1D_ERR(EINVAL));

    validate_input_or_ret(sz > 0 && sz <= SIZE_MAX / 2, DAV1D_ERR(EINVAL));

    GetBits gb;

    dav1d_init_get_bits(&gb, ptr, sz);

    int res = DAV1D_ERR(ENOENT);

    do {

        dav1d_get_bit(&gb); // obu_forbidden_bit

        const enum Dav1dObuType type = dav1d_get_bits(&gb, 4);

        const int has_extension = dav1d_get_bit(&gb);

        const int has_length_field = dav1d_get_bit(&gb);

        dav1d_get_bits(&gb, 1 + 8 * has_extension); // ignore

        const uint8_t *obu_end = gb.ptr_end;

        if (has_length_field) {

            const size_t len = dav1d_get_uleb128(&gb);

            if (len > (size_t)(obu_end - gb.ptr)) return DAV1D_ERR(EINVAL);

            obu_end = gb.ptr + len;

        }

        if (type == DAV1D_OBU_SEQ_HDR) {

            if ((res = parse_seq_hdr(out, &gb, 0)) < 0) return res;

            if (gb.ptr > obu_end) return DAV1D_ERR(EINVAL);

            dav1d_bytealign_get_bits(&gb);

        }

        if (gb.error) return DAV1D_ERR(EINVAL);

        assert(gb.state == 0 && gb.bits_left == 0);

        gb.ptr = obu_end;

    } while (gb.ptr < gb.ptr_end);

    return res;

}

static int read_frame_size(Dav1dContext *const c, GetBits *const gb,

                           const int use_ref)

{

    const Dav1dSequenceHeader *const seqhdr = c->seq_hdr;

    Dav1dFrameHeader *const hdr = c->frame_hdr;

    if (use_ref) {

        for (int i = 0; i < 7; i++) {

            if (dav1d_get_bit(gb)) {

                const Dav1dThreadPicture *const ref =

                    &c->refs[c->frame_hdr->refidx[i]].p;

                if (!ref->p.frame_hdr) return -1;

                hdr->width[1] = ref->p.frame_hdr->width[1];

                hdr->height = ref->p.frame_hdr->height;

                hdr->render_width = ref->p.frame_hdr->render_width;

                hdr->render_height = ref->p.frame_hdr->render_height;

                hdr->super_res.enabled = seqhdr->super_res && dav1d_get_bit(gb);

                if (hdr->super_res.enabled) {

                    const int d = hdr->super_res.width_scale_denominator =

                        9 + dav1d_get_bits(gb, 3);

                    hdr->width[0] = imax((hdr->width[1] * 8 + (d >> 1)) / d,

                                         imin(16, hdr->width[1]));

                } else {

                    hdr->super_res.width_scale_denominator = 8;

                    hdr->width[0] = hdr->width[1];

                }

                return 0;

            }

        }

    }

    if (hdr->frame_size_override) {

        hdr->width[1] = dav1d_get_bits(gb, seqhdr->width_n_bits) + 1;

        hdr->height = dav1d_get_bits(gb, seqhdr->height_n_bits) + 1;

    } else {

        hdr->width[1] = seqhdr->max_width;

        hdr->height = seqhdr->max_height;

    }

    hdr->super_res.enabled = seqhdr->super_res && dav1d_get_bit(gb);

    if (hdr->super_res.enabled) {

        const int d = hdr->super_res.width_scale_denominator = 9 + dav1d_get_bits(gb, 3);

        hdr->width[0] = imax((hdr->width[1] * 8 + (d >> 1)) / d, imin(16, hdr->width[1]));

    } else {

        hdr->super_res.width_scale_denominator = 8;

        hdr->width[0] = hdr->width[1];

    }

    hdr->have_render_size = dav1d_get_bit(gb);

    if (hdr->have_render_size) {

        hdr->render_width = dav1d_get_bits(gb, 16) + 1;

        hdr->render_height = dav1d_get_bits(gb, 16) + 1;

    } else {

        hdr->render_width = hdr->width[1];

        hdr->render_height = hdr->height;

    }

    return 0;

}

static inline int tile_log2(const int sz, const int tgt) {

    int k;

    for (k = 0; (sz << k) < tgt; k++) ;

    return k;

}

static const Dav1dLoopfilterModeRefDeltas default_mode_ref_deltas = {

    .mode_delta = { 0, 0 },

    .ref_delta = { 1, 0, 0, 0, -1, 0, -1, -1 },

};

static int parse_frame_hdr(Dav1dContext *const c, GetBits *const gb) {

#define DEBUG_FRAME_HDR 0

#if DEBUG_FRAME_HDR

    const uint8_t *const init_ptr = gb->ptr;

#endif

    const Dav1dSequenceHeader *const seqhdr = c->seq_hdr;

    Dav1dFrameHeader *const hdr = c->frame_hdr;

    if (!seqhdr->reduced_still_picture_header)

        hdr->show_existing_frame = dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-show_existing_frame: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (hdr->show_existing_frame) {

        hdr->existing_frame_idx = dav1d_get_bits(gb, 3);

        if (seqhdr->decoder_model_info_present && !seqhdr->equal_picture_interval)

            hdr->frame_presentation_delay = dav1d_get_bits(gb, seqhdr->frame_presentation_delay_length);

        if (seqhdr->frame_id_numbers_present) {

            hdr->frame_id = dav1d_get_bits(gb, seqhdr->frame_id_n_bits);

            Dav1dFrameHeader *const ref_frame_hdr = c->refs[hdr->existing_frame_idx].p.p.frame_hdr;

            if (!ref_frame_hdr || ref_frame_hdr->frame_id != hdr->frame_id) goto error;

        }

        return 0;

    }

    if (seqhdr->reduced_still_picture_header) {

        hdr->frame_type = DAV1D_FRAME_TYPE_KEY;

        hdr->show_frame = 1;

    } else {

        hdr->frame_type = dav1d_get_bits(gb, 2);

        hdr->show_frame = dav1d_get_bit(gb);

    }

    if (hdr->show_frame) {

        if (seqhdr->decoder_model_info_present && !seqhdr->equal_picture_interval)

            hdr->frame_presentation_delay = dav1d_get_bits(gb, seqhdr->frame_presentation_delay_length);

        hdr->showable_frame = hdr->frame_type != DAV1D_FRAME_TYPE_KEY;

    } else

        hdr->showable_frame = dav1d_get_bit(gb);

    hdr->error_resilient_mode =

        (hdr->frame_type == DAV1D_FRAME_TYPE_KEY && hdr->show_frame) ||

        hdr->frame_type == DAV1D_FRAME_TYPE_SWITCH ||

        seqhdr->reduced_still_picture_header || dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-frametype_bits: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    hdr->disable_cdf_update = dav1d_get_bit(gb);

    hdr->allow_screen_content_tools = seqhdr->screen_content_tools == DAV1D_ADAPTIVE ?

                                      dav1d_get_bit(gb) : seqhdr->screen_content_tools;

    if (hdr->allow_screen_content_tools)

        hdr->force_integer_mv = seqhdr->force_integer_mv == DAV1D_ADAPTIVE ?

                                dav1d_get_bit(gb) : seqhdr->force_integer_mv;

    if (IS_KEY_OR_INTRA(hdr))

        hdr->force_integer_mv = 1;

    if (seqhdr->frame_id_numbers_present)

        hdr->frame_id = dav1d_get_bits(gb, seqhdr->frame_id_n_bits);

    if (!seqhdr->reduced_still_picture_header)

        hdr->frame_size_override = hdr->frame_type == DAV1D_FRAME_TYPE_SWITCH ? 1 : dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-frame_size_override_flag: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (seqhdr->order_hint)

        hdr->frame_offset = dav1d_get_bits(gb, seqhdr->order_hint_n_bits);

    hdr->primary_ref_frame = !hdr->error_resilient_mode && IS_INTER_OR_SWITCH(hdr) ?

                             dav1d_get_bits(gb, 3) : DAV1D_PRIMARY_REF_NONE;

    if (seqhdr->decoder_model_info_present) {

        hdr->buffer_removal_time_present = dav1d_get_bit(gb);

        if (hdr->buffer_removal_time_present) {

            for (int i = 0; i < c->seq_hdr->num_operating_points; i++) {

                const struct Dav1dSequenceHeaderOperatingPoint *const seqop = &seqhdr->operating_points[i];

                struct Dav1dFrameHeaderOperatingPoint *const op = &hdr->operating_points[i];

                if (seqop->decoder_model_param_present) {

                    int in_temporal_layer = (seqop->idc >> hdr->temporal_id) & 1;

                    int in_spatial_layer  = (seqop->idc >> (hdr->spatial_id + 8)) & 1;

                    if (!seqop->idc || (in_temporal_layer && in_spatial_layer))

                        op->buffer_removal_time = dav1d_get_bits(gb, seqhdr->buffer_removal_delay_length);

                }

            }

        }

    }

    if (IS_KEY_OR_INTRA(hdr)) {

        hdr->refresh_frame_flags = (hdr->frame_type == DAV1D_FRAME_TYPE_KEY &&

                                    hdr->show_frame) ? 0xff : dav1d_get_bits(gb, 8);

        if (hdr->refresh_frame_flags != 0xff && hdr->error_resilient_mode && seqhdr->order_hint)

            for (int i = 0; i < 8; i++)

                dav1d_get_bits(gb, seqhdr->order_hint_n_bits);

        if (c->strict_std_compliance &&

            hdr->frame_type == DAV1D_FRAME_TYPE_INTRA && hdr->refresh_frame_flags == 0xff)

        {

            goto error;

        }

        if (read_frame_size(c, gb, 0) < 0) goto error;

        if (hdr->allow_screen_content_tools && !hdr->super_res.enabled)

            hdr->allow_intrabc = dav1d_get_bit(gb);

    } else {

        hdr->refresh_frame_flags = hdr->frame_type == DAV1D_FRAME_TYPE_SWITCH ? 0xff :

                                   dav1d_get_bits(gb, 8);

        if (hdr->error_resilient_mode && seqhdr->order_hint)

            for (int i = 0; i < 8; i++)

                dav1d_get_bits(gb, seqhdr->order_hint_n_bits);

        if (seqhdr->order_hint) {

            hdr->frame_ref_short_signaling = dav1d_get_bit(gb);

            if (hdr->frame_ref_short_signaling) {

                hdr->refidx[0] = dav1d_get_bits(gb, 3);

                hdr->refidx[1] = hdr->refidx[2] = -1;

                hdr->refidx[3] = dav1d_get_bits(gb, 3);

                /* +1 allows for unconditional stores, as unused

                 * values can be dumped into frame_offset[-1]. */

                int frame_offset_mem[8+1];

                int *const frame_offset = &frame_offset_mem[1];

                int earliest_ref = -1;

                for (int i = 0, earliest_offset = INT_MAX; i < 8; i++) {

                    const Dav1dFrameHeader *const refhdr = c->refs[i].p.p.frame_hdr;

                    if (!refhdr) goto error;

                    const int diff = get_poc_diff(seqhdr->order_hint_n_bits,

                                                  refhdr->frame_offset,

                                                  hdr->frame_offset);

                    frame_offset[i] = diff;

                    if (diff < earliest_offset) {

                        earliest_offset = diff;

                        earliest_ref = i;

                    }

                }

                frame_offset[hdr->refidx[0]] = INT_MIN; // = reference frame is used

                frame_offset[hdr->refidx[3]] = INT_MIN;

                assert(earliest_ref >= 0);

                int refidx = -1;

                for (int i = 0, latest_offset = 0; i < 8; i++) {

                    const int hint = frame_offset[i];

                    if (hint >= latest_offset) {

                        latest_offset = hint;

                        refidx = i;

                    }

                }

                frame_offset[refidx] = INT_MIN;

                hdr->refidx[6] = refidx;

                for (int i = 4; i < 6; i++) {

                    /* Unsigned compares to handle negative values. */

                    unsigned earliest_offset = UINT8_MAX;

                    refidx = -1;

                    for (int j = 0; j < 8; j++) {

                        const unsigned hint = frame_offset[j];

                        if (hint < earliest_offset) {

                            earliest_offset = hint;

                            refidx = j;

                        }

                    }

                    frame_offset[refidx] = INT_MIN;

                    hdr->refidx[i] = refidx;

                }

                for (int i = 1; i < 7; i++) {

                    refidx = hdr->refidx[i];

                    if (refidx < 0) {

                        unsigned latest_offset = ~UINT8_MAX;

                        for (int j = 0; j < 8; j++) {

                            const unsigned hint = frame_offset[j];

                            if (hint >= latest_offset) {

                                latest_offset = hint;

                                refidx = j;

                            }

                        }

                        frame_offset[refidx] = INT_MIN;

                        hdr->refidx[i] = refidx >= 0 ? refidx : earliest_ref;

                    }

                }

            }

        }

        for (int i = 0; i < 7; i++) {

            if (!hdr->frame_ref_short_signaling)

                hdr->refidx[i] = dav1d_get_bits(gb, 3);

            if (seqhdr->frame_id_numbers_present) {

                const unsigned delta_ref_frame_id = dav1d_get_bits(gb, seqhdr->delta_frame_id_n_bits) + 1;

                const unsigned ref_frame_id = (hdr->frame_id + (1 << seqhdr->frame_id_n_bits) - delta_ref_frame_id) & ((1 << seqhdr->frame_id_n_bits) - 1);

                Dav1dFrameHeader *const ref_frame_hdr = c->refs[hdr->refidx[i]].p.p.frame_hdr;

                if (!ref_frame_hdr || ref_frame_hdr->frame_id != ref_frame_id) goto error;

            }

        }

        const int use_ref = !hdr->error_resilient_mode &&

                            hdr->frame_size_override;

        if (read_frame_size(c, gb, use_ref) < 0) goto error;

        if (!hdr->force_integer_mv)

            hdr->hp = dav1d_get_bit(gb);

        hdr->subpel_filter_mode = dav1d_get_bit(gb) ? DAV1D_FILTER_SWITCHABLE :

                                                      dav1d_get_bits(gb, 2);

        hdr->switchable_motion_mode = dav1d_get_bit(gb);

        if (!hdr->error_resilient_mode && seqhdr->ref_frame_mvs &&

            seqhdr->order_hint && IS_INTER_OR_SWITCH(hdr))

        {

            hdr->use_ref_frame_mvs = dav1d_get_bit(gb);

        }

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-frametype-specific-bits: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (!seqhdr->reduced_still_picture_header && !hdr->disable_cdf_update)

        hdr->refresh_context = !dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-refresh_context: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // tile data

    hdr->tiling.uniform = dav1d_get_bit(gb);

    const int sbsz_min1 = (64 << seqhdr->sb128) - 1;

    const int sbsz_log2 = 6 + seqhdr->sb128;

    const int sbw = (hdr->width[0] + sbsz_min1) >> sbsz_log2;

    const int sbh = (hdr->height + sbsz_min1) >> sbsz_log2;

    const int max_tile_width_sb = 4096 >> sbsz_log2;

    const int max_tile_area_sb = 4096 * 2304 >> (2 * sbsz_log2);

    hdr->tiling.min_log2_cols = tile_log2(max_tile_width_sb, sbw);

    hdr->tiling.max_log2_cols = tile_log2(1, imin(sbw, DAV1D_MAX_TILE_COLS));

    hdr->tiling.max_log2_rows = tile_log2(1, imin(sbh, DAV1D_MAX_TILE_ROWS));

    const int min_log2_tiles = imax(tile_log2(max_tile_area_sb, sbw * sbh),

                              hdr->tiling.min_log2_cols);

    if (hdr->tiling.uniform) {

        for (hdr->tiling.log2_cols = hdr->tiling.min_log2_cols;

             hdr->tiling.log2_cols < hdr->tiling.max_log2_cols && dav1d_get_bit(gb);

             hdr->tiling.log2_cols++) ;

        const int tile_w = 1 + ((sbw - 1) >> hdr->tiling.log2_cols);

        hdr->tiling.cols = 0;

        for (int sbx = 0; sbx < sbw; sbx += tile_w, hdr->tiling.cols++)

            hdr->tiling.col_start_sb[hdr->tiling.cols] = sbx;

        hdr->tiling.min_log2_rows =

            imax(min_log2_tiles - hdr->tiling.log2_cols, 0);

        for (hdr->tiling.log2_rows = hdr->tiling.min_log2_rows;

             hdr->tiling.log2_rows < hdr->tiling.max_log2_rows && dav1d_get_bit(gb);

             hdr->tiling.log2_rows++) ;

        const int tile_h = 1 + ((sbh - 1) >> hdr->tiling.log2_rows);

        hdr->tiling.rows = 0;

        for (int sby = 0; sby < sbh; sby += tile_h, hdr->tiling.rows++)

            hdr->tiling.row_start_sb[hdr->tiling.rows] = sby;

    } else {

        hdr->tiling.cols = 0;

        int widest_tile = 0, max_tile_area_sb = sbw * sbh;

        for (int sbx = 0; sbx < sbw && hdr->tiling.cols < DAV1D_MAX_TILE_COLS; hdr->tiling.cols++) {

            const int tile_width_sb = imin(sbw - sbx, max_tile_width_sb);

            const int tile_w = (tile_width_sb > 1) ? 1 + dav1d_get_uniform(gb, tile_width_sb) : 1;

            hdr->tiling.col_start_sb[hdr->tiling.cols] = sbx;

            sbx += tile_w;

            widest_tile = imax(widest_tile, tile_w);

        }

        hdr->tiling.log2_cols = tile_log2(1, hdr->tiling.cols);

        if (min_log2_tiles) max_tile_area_sb >>= min_log2_tiles + 1;

        const int max_tile_height_sb = imax(max_tile_area_sb / widest_tile, 1);

        hdr->tiling.rows = 0;

        for (int sby = 0; sby < sbh && hdr->tiling.rows < DAV1D_MAX_TILE_ROWS; hdr->tiling.rows++) {

            const int tile_height_sb = imin(sbh - sby, max_tile_height_sb);

            const int tile_h = (tile_height_sb > 1) ? 1 + dav1d_get_uniform(gb, tile_height_sb) : 1;

            hdr->tiling.row_start_sb[hdr->tiling.rows] = sby;

            sby += tile_h;

        }

        hdr->tiling.log2_rows = tile_log2(1, hdr->tiling.rows);

    }

    hdr->tiling.col_start_sb[hdr->tiling.cols] = sbw;

    hdr->tiling.row_start_sb[hdr->tiling.rows] = sbh;

    if (hdr->tiling.log2_cols || hdr->tiling.log2_rows) {

        hdr->tiling.update = dav1d_get_bits(gb, hdr->tiling.log2_cols + hdr->tiling.log2_rows);

        if (hdr->tiling.update >= hdr->tiling.cols * hdr->tiling.rows)

            goto error;

        hdr->tiling.n_bytes = dav1d_get_bits(gb, 2) + 1;

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-tiling: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // quant data

    hdr->quant.yac = dav1d_get_bits(gb, 8);

    if (dav1d_get_bit(gb))

        hdr->quant.ydc_delta = dav1d_get_sbits(gb, 7);

    if (!seqhdr->monochrome) {

        // If the sequence header says that delta_q might be different

        // for U, V, we must check whether it actually is for this

        // frame.

        const int diff_uv_delta = seqhdr->separate_uv_delta_q ? dav1d_get_bit(gb) : 0;

        if (dav1d_get_bit(gb))

            hdr->quant.udc_delta = dav1d_get_sbits(gb, 7);

        if (dav1d_get_bit(gb))

            hdr->quant.uac_delta = dav1d_get_sbits(gb, 7);

        if (diff_uv_delta) {

            if (dav1d_get_bit(gb))

                hdr->quant.vdc_delta = dav1d_get_sbits(gb, 7);

            if (dav1d_get_bit(gb))

                hdr->quant.vac_delta = dav1d_get_sbits(gb, 7);

        } else {

            hdr->quant.vdc_delta = hdr->quant.udc_delta;

            hdr->quant.vac_delta = hdr->quant.uac_delta;

        }

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-quant: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    hdr->quant.qm = dav1d_get_bit(gb);

    if (hdr->quant.qm) {

        hdr->quant.qm_y = dav1d_get_bits(gb, 4);

        hdr->quant.qm_u = dav1d_get_bits(gb, 4);

        hdr->quant.qm_v = seqhdr->separate_uv_delta_q ? dav1d_get_bits(gb, 4) :

                                                        hdr->quant.qm_u;

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-qm: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // segmentation data

    hdr->segmentation.enabled = dav1d_get_bit(gb);

    if (hdr->segmentation.enabled) {

        if (hdr->primary_ref_frame == DAV1D_PRIMARY_REF_NONE) {

            hdr->segmentation.update_map = 1;

            hdr->segmentation.update_data = 1;

        } else {

            hdr->segmentation.update_map = dav1d_get_bit(gb);

            if (hdr->segmentation.update_map)

                hdr->segmentation.temporal = dav1d_get_bit(gb);

            hdr->segmentation.update_data = dav1d_get_bit(gb);

        }

        if (hdr->segmentation.update_data) {

            hdr->segmentation.seg_data.last_active_segid = -1;

            for (int i = 0; i < DAV1D_MAX_SEGMENTS; i++) {

                Dav1dSegmentationData *const seg =

                    &hdr->segmentation.seg_data.d[i];

                if (dav1d_get_bit(gb)) {

                    seg->delta_q = dav1d_get_sbits(gb, 9);

                    hdr->segmentation.seg_data.last_active_segid = i;

                }

                if (dav1d_get_bit(gb)) {

                    seg->delta_lf_y_v = dav1d_get_sbits(gb, 7);

                    hdr->segmentation.seg_data.last_active_segid = i;

                }

                if (dav1d_get_bit(gb)) {

                    seg->delta_lf_y_h = dav1d_get_sbits(gb, 7);

                    hdr->segmentation.seg_data.last_active_segid = i;

                }

                if (dav1d_get_bit(gb)) {

                    seg->delta_lf_u = dav1d_get_sbits(gb, 7);

                    hdr->segmentation.seg_data.last_active_segid = i;

                }

                if (dav1d_get_bit(gb)) {

                    seg->delta_lf_v = dav1d_get_sbits(gb, 7);

                    hdr->segmentation.seg_data.last_active_segid = i;

                }

                if (dav1d_get_bit(gb)) {

                    seg->ref = dav1d_get_bits(gb, 3);

                    hdr->segmentation.seg_data.last_active_segid = i;

                    hdr->segmentation.seg_data.preskip = 1;

                } else {

                    seg->ref = -1;

                }

                if ((seg->skip = dav1d_get_bit(gb))) {

                    hdr->segmentation.seg_data.last_active_segid = i;

                    hdr->segmentation.seg_data.preskip = 1;

                }

                if ((seg->globalmv = dav1d_get_bit(gb))) {

                    hdr->segmentation.seg_data.last_active_segid = i;

                    hdr->segmentation.seg_data.preskip = 1;

                }

            }

        } else {

            // segmentation.update_data was false so we should copy

            // segmentation data from the reference frame.

            assert(hdr->primary_ref_frame != DAV1D_PRIMARY_REF_NONE);

            const int pri_ref = hdr->refidx[hdr->primary_ref_frame];

            if (!c->refs[pri_ref].p.p.frame_hdr) goto error;

            hdr->segmentation.seg_data =

                c->refs[pri_ref].p.p.frame_hdr->segmentation.seg_data;

        }

    } else {

        for (int i = 0; i < DAV1D_MAX_SEGMENTS; i++)

            hdr->segmentation.seg_data.d[i].ref = -1;

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-segmentation: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // delta q

    if (hdr->quant.yac) {

        hdr->delta.q.present = dav1d_get_bit(gb);

        if (hdr->delta.q.present) {

            hdr->delta.q.res_log2 = dav1d_get_bits(gb, 2);

            if (!hdr->allow_intrabc) {

                hdr->delta.lf.present = dav1d_get_bit(gb);

                if (hdr->delta.lf.present) {

                    hdr->delta.lf.res_log2 = dav1d_get_bits(gb, 2);

                    hdr->delta.lf.multi = dav1d_get_bit(gb);

                }

            }

        }

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-delta_q_lf_flags: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // derive lossless flags

    const int delta_lossless = !hdr->quant.ydc_delta && !hdr->quant.udc_delta &&

        !hdr->quant.uac_delta && !hdr->quant.vdc_delta && !hdr->quant.vac_delta;

    hdr->all_lossless = 1;

    for (int i = 0; i < DAV1D_MAX_SEGMENTS; i++) {

        hdr->segmentation.qidx[i] = hdr->segmentation.enabled ?

            iclip_u8(hdr->quant.yac + hdr->segmentation.seg_data.d[i].delta_q) :

            hdr->quant.yac;

        hdr->segmentation.lossless[i] =

            !hdr->segmentation.qidx[i] && delta_lossless;

        hdr->all_lossless &= hdr->segmentation.lossless[i];

    }

    // loopfilter

    if (hdr->all_lossless || hdr->allow_intrabc) {

        hdr->loopfilter.mode_ref_delta_enabled = 1;

        hdr->loopfilter.mode_ref_delta_update = 1;

        hdr->loopfilter.mode_ref_deltas = default_mode_ref_deltas;

    } else {

        hdr->loopfilter.level_y[0] = dav1d_get_bits(gb, 6);

        hdr->loopfilter.level_y[1] = dav1d_get_bits(gb, 6);

        if (!seqhdr->monochrome &&

            (hdr->loopfilter.level_y[0] || hdr->loopfilter.level_y[1]))

        {

            hdr->loopfilter.level_u = dav1d_get_bits(gb, 6);

            hdr->loopfilter.level_v = dav1d_get_bits(gb, 6);

        }

        hdr->loopfilter.sharpness = dav1d_get_bits(gb, 3);

        if (hdr->primary_ref_frame == DAV1D_PRIMARY_REF_NONE) {

            hdr->loopfilter.mode_ref_deltas = default_mode_ref_deltas;

        } else {

            const int ref = hdr->refidx[hdr->primary_ref_frame];

            if (!c->refs[ref].p.p.frame_hdr) goto error;

            hdr->loopfilter.mode_ref_deltas =

                c->refs[ref].p.p.frame_hdr->loopfilter.mode_ref_deltas;

        }

        hdr->loopfilter.mode_ref_delta_enabled = dav1d_get_bit(gb);

        if (hdr->loopfilter.mode_ref_delta_enabled) {

            hdr->loopfilter.mode_ref_delta_update = dav1d_get_bit(gb);

            if (hdr->loopfilter.mode_ref_delta_update) {

                for (int i = 0; i < 8; i++)

                    if (dav1d_get_bit(gb))

                        hdr->loopfilter.mode_ref_deltas.ref_delta[i] =

                            dav1d_get_sbits(gb, 7);

                for (int i = 0; i < 2; i++)

                    if (dav1d_get_bit(gb))

                        hdr->loopfilter.mode_ref_deltas.mode_delta[i] =

                            dav1d_get_sbits(gb, 7);

            }

        }

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-lpf: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // cdef

    if (!hdr->all_lossless && seqhdr->cdef && !hdr->allow_intrabc) {

        hdr->cdef.damping = dav1d_get_bits(gb, 2) + 3;

        hdr->cdef.n_bits = dav1d_get_bits(gb, 2);

        for (int i = 0; i < (1 << hdr->cdef.n_bits); i++) {

            hdr->cdef.y_strength[i] = dav1d_get_bits(gb, 6);

            if (!seqhdr->monochrome)

                hdr->cdef.uv_strength[i] = dav1d_get_bits(gb, 6);

        }

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-cdef: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    // restoration

    if ((!hdr->all_lossless || hdr->super_res.enabled) &&

        seqhdr->restoration && !hdr->allow_intrabc)

    {

        hdr->restoration.type[0] = dav1d_get_bits(gb, 2);

        if (!seqhdr->monochrome) {

            hdr->restoration.type[1] = dav1d_get_bits(gb, 2);

            hdr->restoration.type[2] = dav1d_get_bits(gb, 2);

        }

        if (hdr->restoration.type[0] || hdr->restoration.type[1] ||

            hdr->restoration.type[2])

        {

            // Log2 of the restoration unit size.

            hdr->restoration.unit_size[0] = 6 + seqhdr->sb128;

            if (dav1d_get_bit(gb)) {

                hdr->restoration.unit_size[0]++;

                if (!seqhdr->sb128)

                    hdr->restoration.unit_size[0] += dav1d_get_bit(gb);

            }

            hdr->restoration.unit_size[1] = hdr->restoration.unit_size[0];

            if ((hdr->restoration.type[1] || hdr->restoration.type[2]) &&

                seqhdr->ss_hor == 1 && seqhdr->ss_ver == 1)

            {

                hdr->restoration.unit_size[1] -= dav1d_get_bit(gb);

            }

        } else {

            hdr->restoration.unit_size[0] = 8;

        }

    }

#if DEBUG_FRAME_HDR

    printf("HDR: post-restoration: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (!hdr->all_lossless)

        hdr->txfm_mode = dav1d_get_bit(gb) ? DAV1D_TX_SWITCHABLE : DAV1D_TX_LARGEST;

#if DEBUG_FRAME_HDR

    printf("HDR: post-txfmmode: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (IS_INTER_OR_SWITCH(hdr))

        hdr->switchable_comp_refs = dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-refmode: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (hdr->switchable_comp_refs && IS_INTER_OR_SWITCH(hdr) && seqhdr->order_hint) {

        const int poc = hdr->frame_offset;

        int off_before = -1, off_after = -1;

        int off_before_idx, off_after_idx;

        for (int i = 0; i < 7; i++) {

            if (!c->refs[hdr->refidx[i]].p.p.frame_hdr) goto error;

            const int refpoc = c->refs[hdr->refidx[i]].p.p.frame_hdr->frame_offset;

            const int diff = get_poc_diff(seqhdr->order_hint_n_bits, refpoc, poc);

            if (diff > 0) {

                if (off_after < 0 || get_poc_diff(seqhdr->order_hint_n_bits,

                                                  off_after, refpoc) > 0)

                {

                    off_after = refpoc;

                    off_after_idx = i;

                }

            } else if (diff < 0 && (off_before < 0 ||

                                    get_poc_diff(seqhdr->order_hint_n_bits,

                                                 refpoc, off_before) > 0))

            {

                off_before = refpoc;

                off_before_idx = i;

            }

        }

        if ((off_before | off_after) >= 0) {

            hdr->skip_mode_refs[0] = imin(off_before_idx, off_after_idx);

            hdr->skip_mode_refs[1] = imax(off_before_idx, off_after_idx);

            hdr->skip_mode_allowed = 1;

        } else if (off_before >= 0) {

            int off_before2 = -1;

            int off_before2_idx;

            for (int i = 0; i < 7; i++) {

                if (!c->refs[hdr->refidx[i]].p.p.frame_hdr) goto error;

                const int refpoc = c->refs[hdr->refidx[i]].p.p.frame_hdr->frame_offset;

                if (get_poc_diff(seqhdr->order_hint_n_bits,

                                 refpoc, off_before) < 0) {

                    if (off_before2 < 0 || get_poc_diff(seqhdr->order_hint_n_bits,

                                                        refpoc, off_before2) > 0)

                    {

                        off_before2 = refpoc;

                        off_before2_idx = i;

                    }

                }

            }

            if (off_before2 >= 0) {

                hdr->skip_mode_refs[0] = imin(off_before_idx, off_before2_idx);

                hdr->skip_mode_refs[1] = imax(off_before_idx, off_before2_idx);

                hdr->skip_mode_allowed = 1;

            }

        }

    }

    if (hdr->skip_mode_allowed)

        hdr->skip_mode_enabled = dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-extskip: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    if (!hdr->error_resilient_mode && IS_INTER_OR_SWITCH(hdr) && seqhdr->warped_motion)

        hdr->warp_motion = dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-warpmotionbit: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    hdr->reduced_txtp_set = dav1d_get_bit(gb);

#if DEBUG_FRAME_HDR

    printf("HDR: post-reducedtxtpset: off=%td\n",

           (gb->ptr - init_ptr) * 8 - gb->bits_left);

#endif

    for (int i = 0; i < 7; i++)

        hdr->gmv[i] = dav1d_default_wm_params;