/*

 * VC-1 and WMV3 parser

 * Copyright (c) 2006-2007 Konstantin Shishkov

 * Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer

 *

 * 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

 * VC-1 and WMV3 parser

 */

#include "libavutil/attributes.h"

#include "libavutil/avassert.h"

#include "parser.h"

#include "parser_internal.h"

#include "vc1.h"

#include "get_bits.h"

#include "vc1dsp.h"

/** The maximum number of bytes of a sequence, entry point or

 *  frame header whose values we pay any attention to */

#define UNESCAPED_THRESHOLD 37

/** The maximum number of bytes of a sequence, entry point or

 *  frame header which must be valid memory (because they are

 *  used to update the bitstream cache in skip_bits() calls)

 */

#define UNESCAPED_LIMIT 144

typedef enum {

    NO_MATCH,

    ONE_ZERO,

    TWO_ZEROS,

    ONE

} VC1ParseSearchState;

typedef struct VC1ParseContext {

    ParseContext pc;

    VC1Context v;

    uint8_t prev_start_code;

    size_t bytes_to_skip;

    uint8_t unesc_buffer[UNESCAPED_LIMIT];

    size_t unesc_index;

    VC1ParseSearchState search_state;

} VC1ParseContext;

static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,

                               const uint8_t *buf, int buf_size)

{

    /* Parse the header we just finished unescaping */

    VC1ParseContext *vpc = s->priv_data;

    GetBitContext gb;

    int ret;

    vpc->v.s.avctx = avctx;

    ret = init_get_bits8(&gb, buf, buf_size);

    av_assert1(ret >= 0); // buf_size is bounded by UNESCAPED_THRESHOLD

    switch (vpc->prev_start_code) {

    case VC1_CODE_SEQHDR & 0xFF:

        ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);

        break;

    case VC1_CODE_ENTRYPOINT & 0xFF:

        ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);

        break;

    case VC1_CODE_FRAME & 0xFF:

        if(vpc->v.profile < PROFILE_ADVANCED)

            ret = ff_vc1_parse_frame_header    (&vpc->v, &gb);

        else

            ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);

        if (ret < 0)

            break;

        /* keep AV_PICTURE_TYPE_BI internal to VC1 */

        if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)

            s->pict_type = AV_PICTURE_TYPE_B;

        else

            s->pict_type = vpc->v.s.pict_type;

        if (vpc->v.broadcast){

            // process pulldown flags

            s->repeat_pict = 1;

            // Pulldown flags are only valid when 'broadcast' has been set.

            if (vpc->v.rff){

                // repeat field

                s->repeat_pict = 2;

            }else if (vpc->v.rptfrm){

                // repeat frames

                s->repeat_pict = vpc->v.rptfrm * 2 + 1;

            }

        }else{

            s->repeat_pict = 0;

        }

        if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)

            s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;

        else

            s->field_order = AV_FIELD_PROGRESSIVE;

        break;

    }

    s->format = vpc->v.chromaformat == 1 ? AV_PIX_FMT_YUV420P

                                         : AV_PIX_FMT_NONE;

    if (avctx->width && avctx->height) {

        s->width        = avctx->width;

        s->height       = avctx->height;

        s->coded_width  = FFALIGN(avctx->coded_width,  16);

        s->coded_height = FFALIGN(avctx->coded_height, 16);

    }

}

static int vc1_parse(AVCodecParserContext *s,

                           AVCodecContext *avctx,

                           const uint8_t **poutbuf, int *poutbuf_size,

                           const uint8_t *buf, int buf_size)

{

    /* Here we do the searching for frame boundaries and headers at

     * the same time. Only a minimal amount at the start of each

     * header is unescaped. */

    VC1ParseContext *vpc = s->priv_data;

    int pic_found = vpc->pc.frame_start_found;

    uint8_t *unesc_buffer = vpc->unesc_buffer;

    size_t unesc_index = vpc->unesc_index;

    VC1ParseSearchState search_state = vpc->search_state;

    int start_code_found = 0;

    int next = END_NOT_FOUND;

    int i = vpc->bytes_to_skip;

    if (pic_found && buf_size == 0) {

        /* EOF considered as end of frame */

        memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);

        vc1_extract_header(s, avctx, unesc_buffer, unesc_index);

        next = 0;

    }

    while (i < buf_size) {

        uint8_t b;

        start_code_found = 0;

        while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {

            b = buf[i++];

            unesc_buffer[unesc_index++] = b;

            if (search_state <= ONE_ZERO)

                search_state = b ? NO_MATCH : search_state + 1;

            else if (search_state == TWO_ZEROS) {

                if (b == 1)

                    search_state = ONE;

                else if (b > 1) {

                    if (b == 3)

                        unesc_index--; // swallow emulation prevention byte

                    search_state = NO_MATCH;

                }

            }

            else { // search_state == ONE

                // Header unescaping terminates early due to detection of next start code

                search_state = NO_MATCH;

                start_code_found = 1;

                break;

            }

        }

        if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&

                unesc_index >= UNESCAPED_THRESHOLD &&

                vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))

        {

            // No need to keep scanning the rest of the buffer for

            // start codes if we know it contains a complete frame and

            // we've already unescaped all we need of the frame header

            vc1_extract_header(s, avctx, unesc_buffer, unesc_index);

            unesc_index = 0;

            break;

        }

        if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {

            while (i < buf_size) {

                if (search_state == NO_MATCH) {

                    i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);

                    if (i < buf_size) {

                        search_state = ONE_ZERO;

                    }

                    i++;

                } else {

                    b = buf[i++];

                    if (search_state == ONE_ZERO)

                        search_state = b ? NO_MATCH : TWO_ZEROS;

                    else if (search_state == TWO_ZEROS) {

                        if (b >= 1)

                            search_state = b == 1 ? ONE : NO_MATCH;

                    }

                    else { // search_state == ONE

                        search_state = NO_MATCH;

                        start_code_found = 1;

                        break;

                    }

                }

            }

        }

        if (start_code_found) {

            vc1_extract_header(s, avctx, unesc_buffer, unesc_index);

            vpc->prev_start_code = b;

            unesc_index = 0;

            if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {

                if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {

                    pic_found = 1;

                }

                else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)

                                   && b != (VC1_CODE_ENDOFSEQ & 0xFF)) {

                    next = i - 4;

                    pic_found = b == (VC1_CODE_FRAME & 0xFF);

                    break;

                }

            }

        }

    }

    vpc->pc.frame_start_found = pic_found;

    vpc->unesc_index = unesc_index;

    vpc->search_state = search_state;

    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {

        next = buf_size;

    } else {

        if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {

            vpc->bytes_to_skip = 0;

            *poutbuf = NULL;

            *poutbuf_size = 0;

            return buf_size;

        }

    }

    /* If we return with a valid pointer to a combined frame buffer

     * then on the next call then we'll have been unhelpfully rewound

     * by up to 4 bytes (depending upon whether the start code

     * overlapped the input buffer, and if so by how much). We don't

     * want this: it will either cause spurious second detections of

     * the start code we've already seen, or cause extra bytes to be

     * inserted at the start of the unescaped buffer. */

    vpc->bytes_to_skip = 4;

    if (next < 0 && next != END_NOT_FOUND)

        vpc->bytes_to_skip += next;

    *poutbuf = buf;

    *poutbuf_size = buf_size;

    return next;

}

static av_cold int vc1_parse_init(AVCodecParserContext *s)

{

    VC1ParseContext *vpc = s->priv_data;

    vpc->v.s.slice_context_count = 1;

    vpc->v.first_pic_header_flag = 1;

    vpc->v.parse_only = 1;

    vpc->prev_start_code = 0;

    vpc->bytes_to_skip = 0;

    vpc->unesc_index = 0;

    vpc->search_state = NO_MATCH;

    ff_vc1dsp_init(&vpc->v.vc1dsp); /* startcode_find_candidate */

    return 0;

}

const FFCodecParser ff_vc1_parser = {

    PARSER_CODEC_LIST(AV_CODEC_ID_VC1),

    .priv_data_size = sizeof(VC1ParseContext),

    .init           = vc1_parse_init,

    .parse          = vc1_parse,

    .close          = ff_parse_close,

};