FFmpeg/libavcodec/hevc_parser.c

/*
 * HEVC Annex B format parser
 *
 * Copyright (C) 2012 - 2013 Guillaume Martres
 *
 * 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 "libavutil/common.h"
#include "parser.h"
#include "hevc.h"

#define START_CODE 0x000001 ///< start_code_prefix_one_3bytes

/**
 * Find the end of the current frame in the bitstream.
 * @return the position of the first byte of the next frame, or END_NOT_FOUND
 */
static int hevc_find_frame_end(AVCodecParserContext *s, const uint8_t *buf, int buf_size)
{
    int i;
    ParseContext *pc = s->priv_data;

    for (i = 0; i < buf_size; i++) {
        int nut;

        pc->state64 = (pc->state64 << 8) | buf[i];

        if (((pc->state64 >> 3 * 8) & 0xFFFFFF) != START_CODE)
            continue;

        nut = (pc->state64 >> 2 * 8 + 1) & 0x3F;
        // Beginning of access unit
        if ((nut >= NAL_VPS && nut <= NAL_AUD) || nut == NAL_SEI_PREFIX ||
            (nut >= 41 && nut <= 44) || (nut >= 48 && nut <= 55)) {
            if (pc->frame_start_found) {
                pc->frame_start_found = 0;
                return i - 5;
            }
        } else if (nut <= NAL_RASL_R ||
                   (nut >= NAL_BLA_W_LP && nut <= NAL_CRA_NUT)) {
            int first_slice_segment_in_pic_flag = buf[i] >> 7;
            if (first_slice_segment_in_pic_flag) {
                if (!pc->frame_start_found) {
                    pc->frame_start_found = 1;
                    s->key_frame = nut >= NAL_BLA_W_LP && nut <= NAL_CRA_NUT;
                } else { // First slice of next frame found
                    pc->frame_start_found = 0;
                    return i - 5;
                }
            }
        }
    }

    return END_NOT_FOUND;
}

static int hevc_parse(AVCodecParserContext *s,
                      AVCodecContext *avctx,
                      const uint8_t **poutbuf, int *poutbuf_size,
                      const uint8_t *buf, int buf_size)
{
    int next;
    ParseContext *pc = s->priv_data;

    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
        next = buf_size;
    } else {
        next = hevc_find_frame_end(s, buf, buf_size);
        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
            *poutbuf = NULL;
            *poutbuf_size = 0;
            return buf_size;
        }
    }

    *poutbuf = buf;
    *poutbuf_size = buf_size;
    return next;
}

// Split after the parameter sets at the beginning of the stream if they exist.
static int hevc_split(AVCodecContext *avctx, const uint8_t *buf, int buf_size)
{
    int i;
    uint32_t state = -1;
    int has_ps = 0;

    for (i = 0; i < buf_size; i++) {
        state = (state << 8) | buf[i];
        if (((state >> 8) & 0xFFFFFF) == START_CODE) {
            int nut = (state >> 1) & 0x3F;
            if (nut >= NAL_VPS && nut <= NAL_PPS) {
                has_ps = 1;
            } else if (has_ps) {
                return i - 3;
            } else { // no parameter set at the beginning of the stream
                return 0;
            }
        }
    }
    return 0;
}

AVCodecParser ff_hevc_parser = {
    .codec_ids      = { AV_CODEC_ID_HEVC },
    .priv_data_size = sizeof(ParseContext),
    .parser_parse   = hevc_parse,
    .parser_close   = ff_parse_close,
    .split          = hevc_split,
};