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/*

 * Copyright (c) 2012 Justin Ruggles

 *

 * 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

 * Vorbis audio parser

 *

 * Determines the duration for each packet.

 */

#include "get_bits.h"

#include "parser.h"

#include "xiph.h"

#include "vorbis_parser.h"

static int parse_id_header(AVCodecContext *avctx, VorbisParseContext *s,

                           const uint8_t *buf, int buf_size)

{

    /* Id header should be 30 bytes */

    if (buf_size < 30) {

        av_log(avctx, AV_LOG_ERROR, "Id header is too short\n");

        return AVERROR_INVALIDDATA;

    }

    /* make sure this is the Id header */

    if (buf[0] != 1) {

        av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Id header\n");

        return AVERROR_INVALIDDATA;

    }

    /* check for header signature */

    if (memcmp(&buf[1], "vorbis", 6)) {

        av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Id header\n");

        return AVERROR_INVALIDDATA;

    }

    if (!(buf[29] & 0x1)) {

        av_log(avctx, AV_LOG_ERROR, "Invalid framing bit in Id header\n");

        return AVERROR_INVALIDDATA;

    }

    s->blocksize[0] = 1 << (buf[28] & 0xF);

    s->blocksize[1] = 1 << (buf[28] >>  4);

    return 0;

}

static int parse_setup_header(AVCodecContext *avctx, VorbisParseContext *s,

                              const uint8_t *buf, int buf_size)

{

    GetBitContext gb, gb0;

    uint8_t *rev_buf;

    int i, ret = 0;

    int got_framing_bit, mode_count, got_mode_header, last_mode_count = 0;

    /* avoid overread */

    if (buf_size < 7) {

        av_log(avctx, AV_LOG_ERROR, "Setup header is too short\n");

        return AVERROR_INVALIDDATA;

    }

    /* make sure this is the Setup header */

    if (buf[0] != 5) {

        av_log(avctx, AV_LOG_ERROR, "Wrong packet type in Setup header\n");

        return AVERROR_INVALIDDATA;

    }

    /* check for header signature */

    if (memcmp(&buf[1], "vorbis", 6)) {

        av_log(avctx, AV_LOG_ERROR, "Invalid packet signature in Setup header\n");

        return AVERROR_INVALIDDATA;

    }

    /* reverse bytes so we can easily read backwards with get_bits() */

    if (!(rev_buf = av_malloc(buf_size))) {

        av_log(avctx, AV_LOG_ERROR, "Out of memory\n");

        return AVERROR(ENOMEM);

    }

    for (i = 0; i < buf_size; i++)

        rev_buf[i] = buf[buf_size - 1 - i];

    init_get_bits(&gb, rev_buf, buf_size * 8);

    got_framing_bit = 0;

    while (get_bits_left(&gb) > 97) {

        if (get_bits1(&gb)) {

            got_framing_bit = get_bits_count(&gb);

            break;

        }

    }

    if (!got_framing_bit) {

        av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");

        ret = AVERROR_INVALIDDATA;

        goto bad_header;

    }

    /* Now we search backwards to find possible valid mode counts. This is not

     * fool-proof because we could have false positive matches and read too

     * far, but there isn't really any way to be sure without parsing through

     * all the many variable-sized fields before the modes. This approach seems

     * to work well in testing, and it is similar to how it is handled in

     * liboggz. */

    mode_count = 0;

    got_mode_header = 0;

    while (get_bits_left(&gb) >= 97) {

        if (get_bits(&gb, 8) > 63 || get_bits(&gb, 16) || get_bits(&gb, 16))

            break;

        skip_bits(&gb, 1);

        mode_count++;

        if (mode_count > 64)

            break;

        gb0 = gb;

        if (get_bits(&gb0, 6) + 1 == mode_count) {

            got_mode_header = 1;

            last_mode_count = mode_count;

        }

    }

    if (!got_mode_header) {

        av_log(avctx, AV_LOG_ERROR, "Invalid Setup header\n");

        ret = AVERROR_INVALIDDATA;

        goto bad_header;

    }

    /* All samples I've seen use <= 2 modes, so ask for a sample if we find

     * more than that, as it is most likely a false positive. If we get any

     * we may need to approach this the long way and parse the whole Setup

     * header, but I hope very much that it never comes to that. */

    if (last_mode_count > 2) {

        avpriv_request_sample(avctx,

                              "%d modes (either a false positive or a "

                              "sample from an unknown encoder)",

                              last_mode_count);

    }

    /* We're limiting the mode count to 63 so that we know that the previous

     * block flag will be in the first packet byte. */

    if (last_mode_count > 63) {

        av_log(avctx, AV_LOG_ERROR, "Unsupported mode count: %d\n",

               last_mode_count);

        ret = AVERROR_INVALIDDATA;

        goto bad_header;

    }

    s->mode_count = mode_count = last_mode_count;

    /* Determine the number of bits required to code the mode and turn that

     * into a bitmask to directly access the mode from the first frame byte. */

    s->mode_mask = ((1 << (av_log2(mode_count - 1) + 1)) - 1) << 1;

    /* The previous window flag is the next bit after the mode */

    s->prev_mask = (s->mode_mask | 0x1) + 1;

    init_get_bits(&gb, rev_buf, buf_size * 8);

    skip_bits_long(&gb, got_framing_bit);

    for (i = mode_count - 1; i >= 0; i--) {

        skip_bits_long(&gb, 40);

        s->mode_blocksize[i] = get_bits1(&gb);

    }

bad_header:

    av_free(rev_buf);

    return ret;

}

int avpriv_vorbis_parse_extradata(AVCodecContext *avctx, VorbisParseContext *s)

{

    uint8_t *header_start[3];

    int header_len[3];

    int ret;

    s->avctx = avctx;

    s->extradata_parsed = 1;

    if ((ret = avpriv_split_xiph_headers(avctx->extradata,

                                         avctx->extradata_size, 30,

                                         header_start, header_len)) < 0) {

        av_log(avctx, AV_LOG_ERROR, "Extradata corrupt.\n");

        return ret;

    }

    if ((ret = parse_id_header(avctx, s, header_start[0], header_len[0])) < 0)

        return ret;

    if ((ret = parse_setup_header(avctx, s, header_start[2], header_len[2])) < 0)

        return ret;

    s->valid_extradata = 1;

    s->previous_blocksize = s->blocksize[s->mode_blocksize[0]];

    return 0;

}

int avpriv_vorbis_parse_frame(VorbisParseContext *s, const uint8_t *buf,

                              int buf_size)

{

    int duration = 0;

    if (s->valid_extradata && buf_size > 0) {

        int mode, current_blocksize;

        int previous_blocksize = s->previous_blocksize;

        if (buf[0] & 1) {

            av_log(s->avctx, AV_LOG_ERROR, "Invalid packet\n");

            return AVERROR_INVALIDDATA;

        }

        if (s->mode_count == 1)

            mode = 0;

        else

            mode = (buf[0] & s->mode_mask) >> 1;

        if (mode >= s->mode_count) {

            av_log(s->avctx, AV_LOG_ERROR, "Invalid mode in packet\n");

            return AVERROR_INVALIDDATA;

        }

        if(s->mode_blocksize[mode]){

            int flag = !!(buf[0] & s->prev_mask);

            previous_blocksize = s->blocksize[flag];

        }

        current_blocksize     = s->blocksize[s->mode_blocksize[mode]];

        duration              = (previous_blocksize + current_blocksize) >> 2;

        s->previous_blocksize = current_blocksize;

    }

    return duration;

}

void avpriv_vorbis_parse_reset(VorbisParseContext *s)

{

    if (s->valid_extradata)

        s->previous_blocksize = s->blocksize[0];

}

#if CONFIG_VORBIS_PARSER

static int vorbis_parse(AVCodecParserContext *s1, AVCodecContext *avctx,

                        const uint8_t **poutbuf, int *poutbuf_size,

                        const uint8_t *buf, int buf_size)

{

    VorbisParseContext *s = s1->priv_data;

    int duration;

    if (!s->extradata_parsed && avctx->extradata && avctx->extradata_size)

        if (avpriv_vorbis_parse_extradata(avctx, s))

            goto end;

    if ((duration = avpriv_vorbis_parse_frame(s, buf, buf_size)) >= 0)

        s1->duration = duration;

end:

    /* always return the full packet. this parser isn't doing any splitting or

       combining, only packet analysis */

    *poutbuf      = buf;

    *poutbuf_size = buf_size;

    return buf_size;

}

AVCodecParser ff_vorbis_parser = {

    .codec_ids      = { AV_CODEC_ID_VORBIS },

    .priv_data_size = sizeof(VorbisParseContext),

    .parser_parse   = vorbis_parse,

};

#endif /* CONFIG_VORBIS_PARSER */