/*

 * Copyright (c) 2019 James Almer <jamrial@gmail.com>

 *

 * 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

 */

/**

 * @file

 * This bitstream filter splits AV1 Temporal Units into packets containing

 * just one frame, plus any leading and trailing OBUs that may be present at

 * the beginning or end, respectively.

 *

 * Temporal Units already containing only one frame will be passed through

 * unchanged. When splitting can't be performed, the Temporal Unit will be

 * passed through containing only the remaining OBUs starting from the first

 * one after the last successfully split frame.

 */

#include "libavutil/avassert.h"

#include "bsf.h"

#include "bsf_internal.h"

#include "cbs.h"

#include "cbs_av1.h"

typedef struct AV1FSplitContext {

    AVPacket *buffer_pkt;

    CodedBitstreamContext *cbc;

    CodedBitstreamFragment temporal_unit;

    int nb_frames;

    int cur_frame;

    int cur_frame_idx;

    int last_frame_idx;

} AV1FSplitContext;

static int av1_frame_split_filter(AVBSFContext *ctx, AVPacket *out)

{

    AV1FSplitContext *s = ctx->priv_data;

    CodedBitstreamFragment *td = &s->temporal_unit;

    int i, ret;

    int split = !!s->buffer_pkt->data;

    if (!s->buffer_pkt->data) {

        int nb_frames = 0;

        ret = ff_bsf_get_packet_ref(ctx, s->buffer_pkt);

        if (ret < 0)

            return ret;

        ret = ff_cbs_read_packet(s->cbc, td, s->buffer_pkt);

        if (ret < 0) {

            av_log(ctx, AV_LOG_WARNING, "Failed to parse temporal unit.\n");

            goto passthrough;

        }

        for (i = 0; i < td->nb_units; i++) {

            CodedBitstreamUnit *unit = &td->units[i];

            if (unit->type == AV1_OBU_FRAME ||

                unit->type == AV1_OBU_FRAME_HEADER)

                nb_frames++;

            else if (unit->type == AV1_OBU_TILE_LIST) {

                av_log(ctx, AV_LOG_VERBOSE, "Large scale tiles are unsupported.\n");

                goto passthrough;

            }

        }

        if (nb_frames > 1) {

            s->cur_frame = 0;

            s->cur_frame_idx = s->last_frame_idx = 0;

            s->nb_frames = nb_frames;

            split = 1;

        }

    }

    if (split) {

        AV1RawFrameHeader *frame = NULL;

        int cur_frame_type = -1, size = 0;

        for (i = s->cur_frame_idx; i < td->nb_units; i++) {

            CodedBitstreamUnit *unit = &td->units[i];

            size += unit->data_size;

            if (unit->type == AV1_OBU_FRAME) {

                AV1RawOBU *obu = unit->content;

                if (frame) {

                    av_log(ctx, AV_LOG_WARNING, "Frame OBU found when Tile data for a "

                                                "previous frame was expected.\n");

                    goto passthrough;

                }

                frame = &obu->obu.frame.header;

                cur_frame_type = obu->header.obu_type;

                s->last_frame_idx = s->cur_frame_idx;

                s->cur_frame_idx  = i + 1;

                s->cur_frame++;

                // split here unless it's the last frame, in which case

                // include every trailing OBU

                if (s->cur_frame < s->nb_frames)

                    break;

            } else if (unit->type == AV1_OBU_FRAME_HEADER) {

                AV1RawOBU *obu = unit->content;

                if (frame) {

                    av_log(ctx, AV_LOG_WARNING, "Frame Header OBU found when Tile data for a "

                                                "previous frame was expected.\n");

                    goto passthrough;

                }

                frame = &obu->obu.frame_header;

                cur_frame_type = obu->header.obu_type;

                s->last_frame_idx = s->cur_frame_idx;

                s->cur_frame++;

                // split here if show_existing_frame unless it's the last

                // frame, in which case include every trailing OBU

                if (frame->show_existing_frame &&

                    s->cur_frame < s->nb_frames) {

                    s->cur_frame_idx = i + 1;

                    break;

                }

            } else if (unit->type == AV1_OBU_TILE_GROUP) {

                AV1RawOBU *obu = unit->content;

                AV1RawTileGroup *group = &obu->obu.tile_group;

                if (!frame || cur_frame_type != AV1_OBU_FRAME_HEADER) {

                    av_log(ctx, AV_LOG_WARNING, "Unexpected Tile Group OBU found before a "

                                                "Frame Header.\n");

                    goto passthrough;

                }

                if ((group->tg_end == (frame->tile_cols * frame->tile_rows) - 1) &&

                    // include every trailing OBU with the last frame

                    s->cur_frame < s->nb_frames) {

                    s->cur_frame_idx = i + 1;

                    break;

                }

            }

        }

        av_assert0(frame && s->cur_frame <= s->nb_frames);

        ret = av_packet_ref(out, s->buffer_pkt);

        if (ret < 0)

            goto fail;

        out->data = (uint8_t *)td->units[s->last_frame_idx].data;

        out->size = size;

        // skip the frame in the buffer packet if it's split successfully, so it's not present

        // if the packet is passed through in case of failure when splitting another frame.

        s->buffer_pkt->data += size;

        s->buffer_pkt->size -= size;

        if (!frame->show_existing_frame && !frame->show_frame)

            out->pts = AV_NOPTS_VALUE;

        if (s->cur_frame == s->nb_frames) {

            av_packet_unref(s->buffer_pkt);

            ff_cbs_fragment_reset(td);

        }

        return 0;

    }

passthrough:

    av_packet_move_ref(out, s->buffer_pkt);

    ret = 0;

fail:

    if (ret < 0) {

        av_packet_unref(out);

        av_packet_unref(s->buffer_pkt);

    }

    ff_cbs_fragment_reset(td);

    return ret;

}

static const CodedBitstreamUnitType decompose_unit_types[] = {

    AV1_OBU_TEMPORAL_DELIMITER,

    AV1_OBU_SEQUENCE_HEADER,

    AV1_OBU_FRAME_HEADER,

    AV1_OBU_TILE_GROUP,

    AV1_OBU_FRAME,

};

static int av1_frame_split_init(AVBSFContext *ctx)

{

    AV1FSplitContext *s = ctx->priv_data;

    CodedBitstreamFragment *td = &s->temporal_unit;

    int ret;

    s->buffer_pkt = av_packet_alloc();

    if (!s->buffer_pkt)

        return AVERROR(ENOMEM);

    ret = ff_cbs_init(&s->cbc, AV_CODEC_ID_AV1, ctx);

    if (ret < 0)

        return ret;

    s->cbc->decompose_unit_types    = decompose_unit_types;

    s->cbc->nb_decompose_unit_types = FF_ARRAY_ELEMS(decompose_unit_types);

    if (!ctx->par_in->extradata_size)

        return 0;

    ret = ff_cbs_read_extradata(s->cbc, td, ctx->par_in);

    if (ret < 0)

        av_log(ctx, AV_LOG_WARNING, "Failed to parse extradata.\n");

    ff_cbs_fragment_reset(td);

    return 0;

}

static void av1_frame_split_flush(AVBSFContext *ctx)

{

    AV1FSplitContext *s = ctx->priv_data;

    av_packet_unref(s->buffer_pkt);

    ff_cbs_fragment_reset(&s->temporal_unit);

}

static void av1_frame_split_close(AVBSFContext *ctx)

{

    AV1FSplitContext *s = ctx->priv_data;

    av_packet_free(&s->buffer_pkt);

    ff_cbs_fragment_free(&s->temporal_unit);

    ff_cbs_close(&s->cbc);

}

static const enum AVCodecID av1_frame_split_codec_ids[] = {

    AV_CODEC_ID_AV1, AV_CODEC_ID_NONE,

};

const FFBitStreamFilter ff_av1_frame_split_bsf = {

    .p.name         = "av1_frame_split",

    .p.codec_ids    = av1_frame_split_codec_ids,

    .priv_data_size = sizeof(AV1FSplitContext),

    .init           = av1_frame_split_init,

    .flush          = av1_frame_split_flush,

    .close          = av1_frame_split_close,

    .filter         = av1_frame_split_filter,

};