wtvdec.c

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/*
 * Windows Television (WTV) demuxer
 * Copyright (c) 2010-2011 Peter Ross <pross@xvid.org>
 *
 * 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
 * Windows Television (WTV) demuxer
 * @author Peter Ross <pross@xvid.org>
 */
 
#include <inttypes.h>
#include <time.h>
 
#include "libavutil/channel_layout.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/intfloat.h"
#include "libavutil/mem.h"
#include "libavutil/time_internal.h"
#include "avformat.h"
#include "demux.h"
#include "internal.h"
#include "wtv.h"
#include "mpegts.h"
 
/* Macros for formatting GUIDs */
#define PRI_PRETTY_GUID \
    "%08"PRIx32"-%04"PRIx16"-%04"PRIx16"-%02x%02x%02x%02x%02x%02x%02x%02x"
#define ARG_PRETTY_GUID(g) \
    AV_RL32(g),AV_RL16(g+4),AV_RL16(g+6),g[8],g[9],g[10],g[11],g[12],g[13],g[14],g[15]
#define LEN_PRETTY_GUID 35
 
/*
 * File system routines
 */
 
typedef struct WtvFile {
    AVIOContext *pb_filesystem;  /**< file system (AVFormatContext->pb) */
 
    int sector_bits;     /**< sector shift bits; used to convert sector number into pb_filesystem offset */
    uint32_t *sectors;   /**< file allocation table */
    int nb_sectors;      /**< number of sectors */
 
    int error;
    int64_t position;
    int64_t length;
} WtvFile;
 
static int64_t seek_by_sector(AVIOContext *pb, int64_t sector, int64_t offset)
{
    return avio_seek(pb, (sector << WTV_SECTOR_BITS) + offset, SEEK_SET);
}
 
/**
 * @return bytes read, AVERROR_EOF on end of file, or <0 on error
 */
static int wtvfile_read_packet(void *opaque, uint8_t *buf, int buf_size)
{
    WtvFile *wf = opaque;
    AVIOContext *pb = wf->pb_filesystem;
    int nread = 0, n = 0;
 
    if (wf->error || pb->error)
        return -1;
    if (wf->position >= wf->length || avio_feof(pb))
        return AVERROR_EOF;
 
    buf_size = FFMIN(buf_size, wf->length - wf->position);
    while(nread < buf_size) {
        int remaining_in_sector = (1 << wf->sector_bits) - (wf->position & ((1 << wf->sector_bits) - 1));
        int read_request        = FFMIN(buf_size - nread, remaining_in_sector);
 
        n = avio_read(pb, buf, read_request);
        if (n <= 0)
            break;
        nread += n;
        buf += n;
        wf->position += n;
        if (n == remaining_in_sector) {
            int i = wf->position >> wf->sector_bits;
            if (i >= wf->nb_sectors ||
                (wf->sectors[i] != wf->sectors[i - 1] + (1 << (wf->sector_bits - WTV_SECTOR_BITS)) &&
                seek_by_sector(pb, wf->sectors[i], 0) < 0)) {
                wf->error = 1;
                break;
            }
        }
    }
    return nread ? nread : n;
}
 
/**
 * @return position (or file length)
 */
static int64_t wtvfile_seek(void *opaque, int64_t offset, int whence)
{
    WtvFile *wf = opaque;
    AVIOContext *pb = wf->pb_filesystem;
 
    if (whence == AVSEEK_SIZE)
        return wf->length;
    else if (whence == SEEK_CUR)
        offset = wf->position + offset;
    else if (whence == SEEK_END)
        offset = wf->length;
 
    wf->error = offset < 0 || offset >= wf->length ||
                seek_by_sector(pb, wf->sectors[offset >> wf->sector_bits],
                               offset & ((1 << wf->sector_bits) - 1)) < 0;
    wf->position = offset;
    return offset;
}
 
/**
 * read non-zero integers (le32) from input stream
 * @param pb
 * @param[out] data destination
 * @param     count maximum number of integers to read
 * @return    total number of integers read
 */
static int read_ints(AVIOContext *pb, uint32_t *data, int count)
{
    int i, total = 0;
    for (i = 0; i < count; i++) {
        if ((data[total] = avio_rl32(pb)))
           total++;
    }
    return total;
}
 
/**
 * Open file
 * @param first_sector  First sector
 * @param length        Length of file (bytes)
 * @param depth         File allocation table depth
 * @return NULL on error
 */
static AVIOContext * wtvfile_open_sector(unsigned first_sector, uint64_t length, int depth, AVFormatContext *s)
{
    AVIOContext *pb;
    WtvFile *wf;
    uint8_t *buffer;
    int64_t size;
 
    if (seek_by_sector(s->pb, first_sector, 0) < 0)
        return NULL;
 
    wf = av_mallocz(sizeof(WtvFile));
    if (!wf)
        return NULL;
 
    if (depth == 0) {
        wf->sectors = av_malloc(sizeof(uint32_t));
        if (!wf->sectors) {
            av_free(wf);
            return NULL;
        }
        wf->sectors[0]  = first_sector;
        wf->nb_sectors  = 1;
    } else if (depth == 1) {
        wf->sectors = av_malloc(WTV_SECTOR_SIZE);
        if (!wf->sectors) {
            av_free(wf);
            return NULL;
        }
        wf->nb_sectors  = read_ints(s->pb, wf->sectors, WTV_SECTOR_SIZE / 4);
    } else if (depth == 2) {
        uint32_t sectors1[WTV_SECTOR_SIZE / 4];
        int nb_sectors1 = read_ints(s->pb, sectors1, WTV_SECTOR_SIZE / 4);
        int i;
 
        wf->sectors = av_malloc_array(nb_sectors1, 1 << WTV_SECTOR_BITS);
        if (!wf->sectors) {
            av_free(wf);
            return NULL;
        }
        wf->nb_sectors = 0;
        for (i = 0; i < nb_sectors1; i++) {
            if (seek_by_sector(s->pb, sectors1[i], 0) < 0)
                break;
            wf->nb_sectors += read_ints(s->pb, wf->sectors + i * WTV_SECTOR_SIZE / 4, WTV_SECTOR_SIZE / 4);
        }
    } else {
        av_log(s, AV_LOG_ERROR, "unsupported file allocation table depth (0x%x)\n", depth);
        av_free(wf);
        return NULL;
    }
    wf->sector_bits = length & (1ULL<<63) ? WTV_SECTOR_BITS : WTV_BIGSECTOR_BITS;
 
    if (!wf->nb_sectors) {
        av_freep(&wf->sectors);
        av_freep(&wf);
        return NULL;
    }
 
    size = avio_size(s->pb);
    if (size >= 0 && (int64_t)wf->sectors[wf->nb_sectors - 1] << WTV_SECTOR_BITS > size)
        av_log(s, AV_LOG_WARNING, "truncated file\n");
 
    /* check length */
    length &= 0xFFFFFFFFFFFF;
    if (length > ((int64_t)wf->nb_sectors << wf->sector_bits)) {
        av_log(s, AV_LOG_WARNING, "reported file length (0x%"PRIx64") exceeds number of available sectors (0x%"PRIx64")\n", length, (int64_t)wf->nb_sectors << wf->sector_bits);
        length = (int64_t)wf->nb_sectors <<  wf->sector_bits;
    }
    wf->length = length;
 
    /* seek to initial sector */
    wf->position = 0;
    if (seek_by_sector(s->pb, wf->sectors[0], 0) < 0) {
        av_freep(&wf->sectors);
        av_freep(&wf);
        return NULL;
    }
 
    wf->pb_filesystem = s->pb;
    buffer = av_malloc(1 << wf->sector_bits);
    if (!buffer) {
        av_freep(&wf->sectors);
        av_freep(&wf);
        return NULL;
    }
 
    pb = avio_alloc_context(buffer, 1 << wf->sector_bits, 0, wf,
                           wtvfile_read_packet, NULL, wtvfile_seek);
    if (!pb) {
        av_freep(&buffer);
        av_freep(&wf->sectors);
        av_freep(&wf);
    }
    return pb;
}
 
/**
 * Open file using filename
 * @param[in]  buf       directory buffer
 * @param      buf_size  directory buffer size
 * @param[in]  filename
 * @param      filename_size size of filename
 * @return NULL on error
 */
static AVIOContext * wtvfile_open2(AVFormatContext *s, const uint8_t *buf, int buf_size, const uint8_t *filename, int filename_size)
{
    const uint8_t *buf_end = buf + buf_size;
 
    while(buf + 48 <= buf_end) {
        int dir_length, name_size, first_sector, depth;
        uint64_t file_length;
        const uint8_t *name;
        if (ff_guidcmp(buf, ff_dir_entry_guid)) {
            av_log(s, AV_LOG_ERROR, "unknown guid "FF_PRI_GUID", expected dir_entry_guid; "
                   "remaining directory entries ignored\n", FF_ARG_GUID(buf));
            break;
        }
        dir_length  = AV_RL16(buf + 16);
        file_length = AV_RL64(buf + 24);
        name_size   = 2 * AV_RL32(buf + 32);
        if (name_size < 0) {
            av_log(s, AV_LOG_ERROR,
                   "bad filename length, remaining directory entries ignored\n");
            break;
        }
        if (dir_length == 0) {
            av_log(s, AV_LOG_ERROR,
                   "bad dir length, remaining directory entries ignored\n");
            break;
        }
        if (48 + (int64_t)name_size > buf_end - buf) {
            av_log(s, AV_LOG_ERROR, "filename exceeds buffer size; remaining directory entries ignored\n");
            break;
        }
        first_sector = AV_RL32(buf + 40 + name_size);
        depth        = AV_RL32(buf + 44 + name_size);
 
        /* compare file name; test optional null terminator */
        name = buf + 40;
        if (name_size >= filename_size &&
            !memcmp(name, filename, filename_size) &&
            (name_size < filename_size + 2 || !AV_RN16(name + filename_size)))
            return wtvfile_open_sector(first_sector, file_length, depth, s);
 
        buf += dir_length;
    }
    return NULL;
}
 
#define wtvfile_open(s, buf, buf_size, filename) \
    wtvfile_open2(s, buf, buf_size, filename, sizeof(filename))
 
/**
 * Close file opened with wtvfile_open_sector(), or wtv_open()
 */
static void wtvfile_close(AVIOContext *pb)
{
    WtvFile *wf = pb->opaque;
    av_freep(&wf->sectors);
    av_freep(&pb->opaque);
    av_freep(&pb->buffer);
    avio_context_free(&pb);
}
 
/*
 * Main demuxer
 */
 
typedef struct WtvStream {
    int seen_data;
} WtvStream;
 
typedef struct WtvContext {
    AVIOContext *pb;       /**< timeline file */
    int64_t epoch;
    int64_t pts;             /**< pts for next data chunk */
    int64_t last_valid_pts;  /**< latest valid pts, used for interactive seeking */
 
    /* maintain private seek index, as the AVIndexEntry->pos is relative to the
       start of the 'timeline' file, not the file system (AVFormatContext->pb) */
    AVIndexEntry *index_entries;
    int nb_index_entries;
    unsigned int index_entries_allocated_size;
} WtvContext;
 
/* WTV GUIDs */
static const ff_asf_guid EVENTID_SubtitleSpanningEvent =
    {0x48,0xC0,0xCE,0x5D,0xB9,0xD0,0x63,0x41,0x87,0x2C,0x4F,0x32,0x22,0x3B,0xE8,0x8A};
static const ff_asf_guid EVENTID_LanguageSpanningEvent =
    {0x6D,0x66,0x92,0xE2,0x02,0x9C,0x8D,0x44,0xAA,0x8D,0x78,0x1A,0x93,0xFD,0xC3,0x95};
static const ff_asf_guid EVENTID_AudioDescriptorSpanningEvent =
    {0x1C,0xD4,0x7B,0x10,0xDA,0xA6,0x91,0x46,0x83,0x69,0x11,0xB2,0xCD,0xAA,0x28,0x8E};
static const ff_asf_guid EVENTID_CtxADescriptorSpanningEvent =
    {0xE6,0xA2,0xB4,0x3A,0x47,0x42,0x34,0x4B,0x89,0x6C,0x30,0xAF,0xA5,0xD2,0x1C,0x24};
static const ff_asf_guid EVENTID_CSDescriptorSpanningEvent =
    {0xD9,0x79,0xE7,0xEf,0xF0,0x97,0x86,0x47,0x80,0x0D,0x95,0xCF,0x50,0x5D,0xDC,0x66};
static const ff_asf_guid EVENTID_DVBScramblingControlSpanningEvent =
    {0xC4,0xE1,0xD4,0x4B,0xA1,0x90,0x09,0x41,0x82,0x36,0x27,0xF0,0x0E,0x7D,0xCC,0x5B};
static const ff_asf_guid EVENTID_StreamIDSpanningEvent =
    {0x68,0xAB,0xF1,0xCA,0x53,0xE1,0x41,0x4D,0xA6,0xB3,0xA7,0xC9,0x98,0xDB,0x75,0xEE};
static const ff_asf_guid EVENTID_TeletextSpanningEvent =
    {0x50,0xD9,0x99,0x95,0x33,0x5F,0x17,0x46,0xAF,0x7C,0x1E,0x54,0xB5,0x10,0xDA,0xA3};
static const ff_asf_guid EVENTID_AudioTypeSpanningEvent =
    {0xBE,0xBF,0x1C,0x50,0x49,0xB8,0xCE,0x42,0x9B,0xE9,0x3D,0xB8,0x69,0xFB,0x82,0xB3};
 
/* Windows media GUIDs */
 
/* Media types */
static const ff_asf_guid mediasubtype_mpeg1payload =
    {0x81,0xEB,0x36,0xE4,0x4F,0x52,0xCE,0x11,0x9F,0x53,0x00,0x20,0xAF,0x0B,0xA7,0x70};
static const ff_asf_guid mediatype_mpeg2_sections =
    {0x6C,0x17,0x5F,0x45,0x06,0x4B,0xCE,0x47,0x9A,0xEF,0x8C,0xAE,0xF7,0x3D,0xF7,0xB5};
static const ff_asf_guid mediatype_mpeg2_pes =
    {0x20,0x80,0x6D,0xE0,0x46,0xDB,0xCF,0x11,0xB4,0xD1,0x00,0x80,0x5F,0x6C,0xBB,0xEA};
static const ff_asf_guid mediatype_mstvcaption =
    {0x89,0x8A,0x8B,0xB8,0x49,0xB0,0x80,0x4C,0xAD,0xCF,0x58,0x98,0x98,0x5E,0x22,0xC1};
 
/* Media subtypes */
static const ff_asf_guid mediasubtype_dvb_subtitle =
    {0xC3,0xCB,0xFF,0x34,0xB3,0xD5,0x71,0x41,0x90,0x02,0xD4,0xC6,0x03,0x01,0x69,0x7F};
static const ff_asf_guid mediasubtype_teletext =
    {0xE3,0x76,0x2A,0xF7,0x0A,0xEB,0xD0,0x11,0xAC,0xE4,0x00,0x00,0xC0,0xCC,0x16,0xBA};
static const ff_asf_guid mediasubtype_dtvccdata =
    {0xAA,0xDD,0x2A,0xF5,0xF0,0x36,0xF5,0x43,0x95,0xEA,0x6D,0x86,0x64,0x84,0x26,0x2A};
static const ff_asf_guid mediasubtype_mpeg2_sections =
    {0x79,0x85,0x9F,0x4A,0xF8,0x6B,0x92,0x43,0x8A,0x6D,0xD2,0xDD,0x09,0xFA,0x78,0x61};
 
static int read_probe(const AVProbeData *p)
{
    return ff_guidcmp(p->buf, ff_wtv_guid) ? 0 : AVPROBE_SCORE_MAX;
}
 
/**
 * Convert win32 FILETIME to ISO-8601 string
 * @return <0 on error
 */
static int filetime_to_iso8601(char *buf, int buf_size, int64_t value)
{
    time_t t = (value / 10000000LL) - 11644473600LL;
    struct tm tmbuf;
    struct tm *tm = gmtime_r(&t, &tmbuf);
    if (!tm)
        return -1;
    if (!strftime(buf, buf_size, "%Y-%m-%d %H:%M:%S", tm))
        return -1;
    return 0;
}
 
/**
 * Convert crazy time (100ns since 1 Jan 0001) to ISO-8601 string
 * @return <0 on error
 */
static int crazytime_to_iso8601(char *buf, int buf_size, int64_t value)
{
    time_t t = (value / 10000000LL) - 719162LL*86400LL;
    struct tm tmbuf;
    struct tm *tm = gmtime_r(&t, &tmbuf);
    if (!tm)
        return -1;
    if (!strftime(buf, buf_size, "%Y-%m-%d %H:%M:%S", tm))
        return -1;
    return 0;
}
 
/**
 * Convert OLE DATE to ISO-8601 string
 * @return <0 on error
 */
static int oledate_to_iso8601(char *buf, int buf_size, int64_t value)
{
    time_t t = (av_int2double(value) - 25569.0) * 86400;
    struct tm tmbuf;
    struct tm *tm= gmtime_r(&t, &tmbuf);
    if (!tm)
        return -1;
    if (!strftime(buf, buf_size, "%Y-%m-%d %H:%M:%S", tm))
        return -1;
    return 0;
}
 
static void get_attachment(AVFormatContext *s, AVIOContext *pb, int length)
{
    char mime[1024];
    char description[1024];
    unsigned int filesize;
    AVStream *st;
    int64_t pos = avio_tell(pb);
 
    avio_get_str16le(pb, INT_MAX, mime, sizeof(mime));
    if (strcmp(mime, "image/jpeg"))
        goto done;
 
    avio_r8(pb);
    avio_get_str16le(pb, INT_MAX, description, sizeof(description));
    filesize = avio_rl32(pb);
    if (!filesize)
        goto done;
 
    if (ff_add_attached_pic(s, NULL, pb, NULL, filesize) < 0)
        goto done;
    st = s->streams[s->nb_streams - 1];
    av_dict_set(&st->metadata, "title", description, 0);
    st->codecpar->codec_id   = AV_CODEC_ID_MJPEG;
    st->id = -1;
done:
    avio_seek(pb, pos + length, SEEK_SET);
}
 
static void get_tag(AVFormatContext *s, AVIOContext *pb, const char *key, int type, int length)
{
    char buf[LEN_PRETTY_GUID + 1], *bufp = buf;
    unsigned dict_flags = 0;
 
    if (!strcmp(key, "WM/MediaThumbType")) {
        avio_skip(pb, length);
        return;
    }
 
    if (type == 0 && length == 4) {
        snprintf(buf, sizeof(buf), "%u", avio_rl32(pb));
    } else if (type == 1) {
        int buflen = FFMIN(length + length / 2U + 1, INT_MAX);
        bufp = av_malloc(buflen);
        if (!bufp)
            return;
        avio_get_str16le(pb, length, bufp, buflen);
        if (!*bufp) {
           av_free(bufp);
           return;
        }
        dict_flags = AV_DICT_DONT_STRDUP_VAL;
    } else if (type == 3 && length == 4) {
        strcpy(buf, avio_rl32(pb) ? "true" : "false");
    } else if (type == 4 && length == 8) {
        int64_t num = avio_rl64(pb);
        if (!strcmp(key, "WM/EncodingTime") ||
            !strcmp(key, "WM/MediaOriginalBroadcastDateTime")) {
            if (filetime_to_iso8601(buf, sizeof(buf), num) < 0)
                return;
        } else if (!strcmp(key, "WM/WMRVEncodeTime") ||
                   !strcmp(key, "WM/WMRVEndTime")) {
            if (crazytime_to_iso8601(buf, sizeof(buf), num) < 0)
                return;
        } else if (!strcmp(key, "WM/WMRVExpirationDate")) {
            if (oledate_to_iso8601(buf, sizeof(buf), num) < 0)
                return;
        } else if (!strcmp(key, "WM/WMRVBitrate"))
            snprintf(buf, sizeof(buf), "%f", av_int2double(num));
        else
            snprintf(buf, sizeof(buf), "%"PRIi64, num);
    } else if (type == 5 && length == 2) {
        snprintf(buf, sizeof(buf), "%u", avio_rl16(pb));
    } else if (type == 6 && length == 16) {
        ff_asf_guid guid;
        avio_read(pb, guid, 16);
        snprintf(buf, sizeof(buf), PRI_PRETTY_GUID, ARG_PRETTY_GUID(guid));
    } else if (type == 2 && !strcmp(key, "WM/Picture")) {
        get_attachment(s, pb, length);
        return;
    } else {
        av_log(s, AV_LOG_WARNING, "unsupported metadata entry; key:%s, type:%d, length:0x%x\n", key, type, length);
        avio_skip(pb, length);
        return;
    }
 
    av_dict_set(&s->metadata, key, bufp, dict_flags);
}
 
/**
 * Parse metadata entries
 */
static void parse_legacy_attrib(AVFormatContext *s, AVIOContext *pb)
{
    ff_asf_guid guid;
    int length, type;
    while(!avio_feof(pb)) {
        char key[1024];
        ff_get_guid(pb, &guid);
        type   = avio_rl32(pb);
        length = avio_rl32(pb);
        if (length <= 0)
            break;
        if (ff_guidcmp(&guid, ff_metadata_guid)) {
            av_log(s, AV_LOG_WARNING, "unknown guid "FF_PRI_GUID", expected metadata_guid; "
                   "remaining metadata entries ignored\n", FF_ARG_GUID(guid));
            break;
        }
        avio_get_str16le(pb, INT_MAX, key, sizeof(key));
        get_tag(s, pb, key, type, length);
    }
 
    ff_metadata_conv(&s->metadata, NULL, ff_asf_metadata_conv);
}
 
/**
 * parse VIDEOINFOHEADER2 structure
 * @return bytes consumed
 */
static int parse_videoinfoheader2(AVFormatContext *s, AVStream *st)
{
    WtvContext *wtv = s->priv_data;
    AVIOContext *pb = wtv->pb;
 
    avio_skip(pb, 72);  // picture aspect ratio is unreliable
    st->codecpar->codec_tag = ff_get_bmp_header(pb, st, NULL);
 
    return 72 + 40;
}
 
/**
 * Parse MPEG1WAVEFORMATEX extradata structure
 */
static void parse_mpeg1waveformatex(AVStream *st)
{
    /* fwHeadLayer */
    switch (AV_RL16(st->codecpar->extradata)) {
    case 0x0001 : st->codecpar->codec_id = AV_CODEC_ID_MP1; break;
    case 0x0002 : st->codecpar->codec_id = AV_CODEC_ID_MP2; break;
    case 0x0004 : st->codecpar->codec_id = AV_CODEC_ID_MP3; break;
    }
 
    st->codecpar->bit_rate = AV_RL32(st->codecpar->extradata + 2); /* dwHeadBitrate */
 
    /* dwHeadMode */
    switch (AV_RL16(st->codecpar->extradata + 6)) {
    case 1 :
    case 2 :
    case 4 : st->codecpar->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
             break;
    case 8 : st->codecpar->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
             break;
    }
}
 
/**
 * Initialise stream
 * @param st Stream to initialise, or NULL to create and initialise new stream
 * @return NULL on error
 */
static AVStream * new_stream(AVFormatContext *s, AVStream *st, int sid, int codec_type)
{
    if (st) {
        if (st->codecpar->extradata) {
            av_freep(&st->codecpar->extradata);
            st->codecpar->extradata_size = 0;
        }
    } else {
        WtvStream *wst = av_mallocz(sizeof(WtvStream));
        if (!wst)
            return NULL;
        st = avformat_new_stream(s, NULL);
        if (!st) {
            av_free(wst);
            return NULL;
        }
        st->id = sid;
        st->priv_data = wst;
    }
    st->codecpar->codec_type = codec_type;
    ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL;
    avpriv_set_pts_info(st, 64, 1, 10000000);
    return st;
}
 
/**
 * parse Media Type structure and populate stream
 * @param st         Stream, or NULL to create new stream
 * @param mediatype  Mediatype GUID
 * @param subtype    Subtype GUID
 * @param formattype Format GUID
 * @param size       Size of format buffer
 * @return NULL on error
 */
static AVStream * parse_media_type(AVFormatContext *s, AVStream *st, int sid,
                                   ff_asf_guid mediatype, ff_asf_guid subtype,
                                   ff_asf_guid formattype, uint64_t size)
{
    WtvContext *wtv = s->priv_data;
    AVIOContext *pb = wtv->pb;
    if (!ff_guidcmp(subtype, ff_mediasubtype_cpfilters_processed) &&
        !ff_guidcmp(formattype, ff_format_cpfilters_processed)) {
        ff_asf_guid actual_subtype;
        ff_asf_guid actual_formattype;
 
        if (size < 32) {
            av_log(s, AV_LOG_WARNING, "format buffer size underflow\n");
            avio_skip(pb, size);
            return NULL;
        }
 
        avio_skip(pb, size - 32);
        ff_get_guid(pb, &actual_subtype);
        ff_get_guid(pb, &actual_formattype);
        if (avio_feof(pb))
            return NULL;
        avio_seek(pb, -size, SEEK_CUR);
 
        st = parse_media_type(s, st, sid, mediatype, actual_subtype, actual_formattype, size - 32);
        avio_skip(pb, 32);
        return st;
    } else if (!ff_guidcmp(mediatype, ff_mediatype_audio)) {
        st = new_stream(s, st, sid, AVMEDIA_TYPE_AUDIO);
        if (!st)
            return NULL;
        if (!ff_guidcmp(formattype, ff_format_waveformatex)) {
            int ret = ff_get_wav_header(s, pb, st->codecpar, size, 0);
            if (ret < 0)
                return NULL;
        } else {
            if (ff_guidcmp(formattype, ff_format_none))
                av_log(s, AV_LOG_WARNING, "unknown formattype:"FF_PRI_GUID"\n", FF_ARG_GUID(formattype));
            avio_skip(pb, size);
        }
 
        if (!memcmp(subtype + 4, (const uint8_t[]){FF_MEDIASUBTYPE_BASE_GUID}, 12)) {
            st->codecpar->codec_id = ff_wav_codec_get_id(AV_RL32(subtype), st->codecpar->bits_per_coded_sample);
        } else if (!ff_guidcmp(subtype, mediasubtype_mpeg1payload)) {
            if (st->codecpar->extradata && st->codecpar->extradata_size >= 22)
                parse_mpeg1waveformatex(st);
            else
                av_log(s, AV_LOG_WARNING, "MPEG1WAVEFORMATEX underflow\n");
        } else {
            st->codecpar->codec_id = ff_codec_guid_get_id(ff_codec_wav_guids, subtype);
            if (st->codecpar->codec_id == AV_CODEC_ID_NONE)
                av_log(s, AV_LOG_WARNING, "unknown subtype:"FF_PRI_GUID"\n", FF_ARG_GUID(subtype));
        }
        return st;
    } else if (!ff_guidcmp(mediatype, ff_mediatype_video)) {
        st = new_stream(s, st, sid, AVMEDIA_TYPE_VIDEO);
        if (!st)
            return NULL;
        if (!ff_guidcmp(formattype, ff_format_videoinfo2)) {
            int consumed = parse_videoinfoheader2(s, st);
            avio_skip(pb, FFMAX(size - consumed, 0));
        } else if (!ff_guidcmp(formattype, ff_format_mpeg2_video)) {
            uint64_t consumed = parse_videoinfoheader2(s, st);
            /* ignore extradata; files produced by windows media center contain meaningless mpeg1 sequence header */
            avio_skip(pb, FFMAX(size - consumed, 0));
        } else {
            if (ff_guidcmp(formattype, ff_format_none))
                av_log(s, AV_LOG_WARNING, "unknown formattype:"FF_PRI_GUID"\n", FF_ARG_GUID(formattype));
            avio_skip(pb, size);
        }
 
        if (!memcmp(subtype + 4, (const uint8_t[]){FF_MEDIASUBTYPE_BASE_GUID}, 12)) {
            st->codecpar->codec_id = ff_codec_get_id(ff_codec_bmp_tags, AV_RL32(subtype));
        } else {
            st->codecpar->codec_id = ff_codec_guid_get_id(ff_video_guids, subtype);
        }
        if (st->codecpar->codec_id == AV_CODEC_ID_NONE)
            av_log(s, AV_LOG_WARNING, "unknown subtype:"FF_PRI_GUID"\n", FF_ARG_GUID(subtype));
        return st;
    } else if (!ff_guidcmp(mediatype, mediatype_mpeg2_pes) &&
               !ff_guidcmp(subtype, mediasubtype_dvb_subtitle)) {
        st = new_stream(s, st, sid, AVMEDIA_TYPE_SUBTITLE);
        if (!st)
            return NULL;
        if (ff_guidcmp(formattype, ff_format_none))
            av_log(s, AV_LOG_WARNING, "unknown formattype:"FF_PRI_GUID"\n", FF_ARG_GUID(formattype));
        avio_skip(pb, size);
        st->codecpar->codec_id = AV_CODEC_ID_DVB_SUBTITLE;
        return st;
    } else if (!ff_guidcmp(mediatype, mediatype_mstvcaption) &&
               (!ff_guidcmp(subtype, mediasubtype_teletext) || !ff_guidcmp(subtype, mediasubtype_dtvccdata))) {
        st = new_stream(s, st, sid, AVMEDIA_TYPE_SUBTITLE);
        if (!st)
            return NULL;
        if (ff_guidcmp(formattype, ff_format_none))
            av_log(s, AV_LOG_WARNING, "unknown formattype:"FF_PRI_GUID"\n", FF_ARG_GUID(formattype));
        avio_skip(pb, size);
        st->codecpar->codec_id = !ff_guidcmp(subtype, mediasubtype_teletext) ? AV_CODEC_ID_DVB_TELETEXT : AV_CODEC_ID_EIA_608;
        return st;
    } else if (!ff_guidcmp(mediatype, mediatype_mpeg2_sections) &&
               !ff_guidcmp(subtype, mediasubtype_mpeg2_sections)) {
        if (ff_guidcmp(formattype, ff_format_none))
            av_log(s, AV_LOG_WARNING, "unknown formattype:"FF_PRI_GUID"\n", FF_ARG_GUID(formattype));
        avio_skip(pb, size);
        return NULL;
    }
 
    av_log(s, AV_LOG_WARNING, "unknown media type, mediatype:"FF_PRI_GUID
                              ", subtype:"FF_PRI_GUID", formattype:"FF_PRI_GUID"\n",
                              FF_ARG_GUID(mediatype), FF_ARG_GUID(subtype), FF_ARG_GUID(formattype));
    avio_skip(pb, size);
    return NULL;
}
 
enum {
    SEEK_TO_DATA = 0,
    SEEK_TO_PTS,
};
 
/**
 * Try to seek over a broken chunk
 * @return <0 on error
 */
static int recover(WtvContext *wtv, uint64_t broken_pos)
{
    AVIOContext *pb = wtv->pb;
    int i;
    for (i = 0; i < wtv->nb_index_entries; i++) {
        if (wtv->index_entries[i].pos > broken_pos) {
            int64_t ret = avio_seek(pb, wtv->index_entries[i].pos, SEEK_SET);
            if (ret < 0)
                return ret;
            wtv->pts = wtv->index_entries[i].timestamp;
            return 0;
         }
     }
     return AVERROR(EIO);
}
 
/**
 * Parse WTV chunks
 * @param mode SEEK_TO_DATA or SEEK_TO_PTS
 * @param seekts timestamp
 * @param[out] len_ptr Length of data chunk
 * @return stream index of data chunk, or <0 on error
 */
static int parse_chunks(AVFormatContext *s, int mode, int64_t seekts, int *len_ptr)
{
    WtvContext *wtv = s->priv_data;
    AVIOContext *pb = wtv->pb;
    while (!avio_feof(pb)) {
        ff_asf_guid g;
        int len, sid, consumed;
 
        ff_get_guid(pb, &g);
        len = avio_rl32(pb);
        if (len < 32 || len > INT_MAX - 7) {
            int ret;
            if (avio_feof(pb))
                return AVERROR_EOF;
            av_log(s, AV_LOG_WARNING, "encountered broken chunk\n");
            if ((ret = recover(wtv, avio_tell(pb) - 20)) < 0)
                return ret;
            continue;
        }
        sid = avio_rl32(pb) & 0x7FFF;
        avio_skip(pb, 8);
        consumed = 32;
 
        if (!ff_guidcmp(g, ff_SBE2_STREAM_DESC_EVENT)) {
            if (ff_find_stream_index(s, sid) < 0) {
                ff_asf_guid mediatype, subtype, formattype;
                int size;
                avio_skip(pb, 28);
                ff_get_guid(pb, &mediatype);
                ff_get_guid(pb, &subtype);
                avio_skip(pb, 12);
                ff_get_guid(pb, &formattype);
                size = avio_rl32(pb);
                if (size < 0 || size > INT_MAX - 92 - consumed)
                    return AVERROR_INVALIDDATA;
                parse_media_type(s, 0, sid, mediatype, subtype, formattype, size);
                consumed += 92 + size;
            }
        } else if (!ff_guidcmp(g, ff_stream2_guid)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0 && s->streams[stream_index]->priv_data && !((WtvStream*)s->streams[stream_index]->priv_data)->seen_data) {
                ff_asf_guid mediatype, subtype, formattype;
                int size;
                avio_skip(pb, 12);
                ff_get_guid(pb, &mediatype);
                ff_get_guid(pb, &subtype);
                avio_skip(pb, 12);
                ff_get_guid(pb, &formattype);
                size = avio_rl32(pb);
                if (size < 0 || size > INT_MAX - 76 - consumed)
                    return AVERROR_INVALIDDATA;
                parse_media_type(s, s->streams[stream_index], sid, mediatype, subtype, formattype, size);
                consumed += 76 + size;
            }
        } else if (!ff_guidcmp(g, EVENTID_AudioDescriptorSpanningEvent) ||
                   !ff_guidcmp(g, EVENTID_CtxADescriptorSpanningEvent) ||
                   !ff_guidcmp(g, EVENTID_CSDescriptorSpanningEvent) ||
                   !ff_guidcmp(g, EVENTID_StreamIDSpanningEvent) ||
                   !ff_guidcmp(g, EVENTID_SubtitleSpanningEvent) ||
                   !ff_guidcmp(g, EVENTID_TeletextSpanningEvent)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0) {
                AVStream *st = s->streams[stream_index];
                uint8_t buf[258];
                const uint8_t *pbuf = buf;
                int buf_size;
 
                avio_skip(pb, 8);
                consumed += 8;
                if (!ff_guidcmp(g, EVENTID_CtxADescriptorSpanningEvent) ||
                    !ff_guidcmp(g, EVENTID_CSDescriptorSpanningEvent)) {
                    avio_skip(pb, 6);
                    consumed += 6;
                }
 
                buf_size = FFMIN(len - consumed, sizeof(buf));
                avio_read(pb, buf, buf_size);
                consumed += buf_size;
                ff_parse_mpeg2_descriptor(s, st, 0, &pbuf, buf + buf_size, NULL, 0, 0, NULL);
            }
        } else if (!ff_guidcmp(g, EVENTID_AudioTypeSpanningEvent)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0) {
                AVStream *st = s->streams[stream_index];
                int audio_type;
                avio_skip(pb, 8);
                audio_type = avio_r8(pb);
                if (audio_type == 2)
                    st->disposition |= AV_DISPOSITION_HEARING_IMPAIRED;
                else if (audio_type == 3)
                    st->disposition |= AV_DISPOSITION_VISUAL_IMPAIRED;
                consumed += 9;
            }
        } else if (!ff_guidcmp(g, EVENTID_DVBScramblingControlSpanningEvent)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0) {
                avio_skip(pb, 12);
                if (avio_rl32(pb))
                    av_log(s, AV_LOG_WARNING, "DVB scrambled stream detected (st:%d), decoding will likely fail\n", stream_index);
                consumed += 16;
            }
        } else if (!ff_guidcmp(g, EVENTID_LanguageSpanningEvent)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0) {
                AVStream *st = s->streams[stream_index];
                uint8_t language[4];
                avio_skip(pb, 12);
                avio_read(pb, language, 3);
                if (language[0]) {
                    language[3] = 0;
                    av_dict_set(&st->metadata, "language", language, 0);
                    if (!strcmp(language, "nar") || !strcmp(language, "NAR"))
                        st->disposition |= AV_DISPOSITION_VISUAL_IMPAIRED;
                }
                consumed += 15;
            }
        } else if (!ff_guidcmp(g, ff_timestamp_guid)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0) {
                avio_skip(pb, 8);
                wtv->pts = avio_rl64(pb);
                consumed += 16;
                if (wtv->pts == -1)
                    wtv->pts = AV_NOPTS_VALUE;
                else {
                    wtv->last_valid_pts = wtv->pts;
                    if (wtv->epoch == AV_NOPTS_VALUE || wtv->pts < wtv->epoch)
                        wtv->epoch = wtv->pts;
                    if (mode == SEEK_TO_PTS && wtv->pts >= seekts) {
                        avio_skip(pb, WTV_PAD8(len) - consumed);
                        return 0;
                    }
                }
            }
        } else if (!ff_guidcmp(g, ff_data_guid)) {
            int stream_index = ff_find_stream_index(s, sid);
            if (mode == SEEK_TO_DATA && stream_index >= 0 && len > 32 && s->streams[stream_index]->priv_data) {
                WtvStream *wst = s->streams[stream_index]->priv_data;
                wst->seen_data = 1;
                if (len_ptr) {
                    *len_ptr = len;
                }
                return stream_index;
            }
        } else if (!ff_guidcmp(g, /* DSATTRIB_WMDRMProtectionInfo */ (const ff_asf_guid){0x83,0x95,0x74,0x40,0x9D,0x6B,0xEC,0x4E,0xB4,0x3C,0x67,0xA1,0x80,0x1E,0x1A,0x9B})) {
            int stream_index = ff_find_stream_index(s, sid);
            if (stream_index >= 0)
                av_log(s, AV_LOG_WARNING, "encrypted stream detected (st:%d), decoding will likely fail\n", stream_index);
        } else if (
            !ff_guidcmp(g, /* DSATTRIB_CAPTURE_STREAMTIME */ (const ff_asf_guid){0x14,0x56,0x1A,0x0C,0xCD,0x30,0x40,0x4F,0xBC,0xBF,0xD0,0x3E,0x52,0x30,0x62,0x07}) ||
            !ff_guidcmp(g, /* DSATTRIB_PBDATAG_ATTRIBUTE */ (const ff_asf_guid){0x79,0x66,0xB5,0xE0,0xB9,0x12,0xCC,0x43,0xB7,0xDF,0x57,0x8C,0xAA,0x5A,0x7B,0x63}) ||
            !ff_guidcmp(g, /* DSATTRIB_PicSampleSeq */ (const ff_asf_guid){0x02,0xAE,0x5B,0x2F,0x8F,0x7B,0x60,0x4F,0x82,0xD6,0xE4,0xEA,0x2F,0x1F,0x4C,0x99}) ||
            !ff_guidcmp(g, /* DSATTRIB_TRANSPORT_PROPERTIES */ ff_DSATTRIB_TRANSPORT_PROPERTIES) ||
            !ff_guidcmp(g, /* dvr_ms_vid_frame_rep_data */ (const ff_asf_guid){0xCC,0x32,0x64,0xDD,0x29,0xE2,0xDB,0x40,0x80,0xF6,0xD2,0x63,0x28,0xD2,0x76,0x1F}) ||
            !ff_guidcmp(g, /* EVENTID_ChannelChangeSpanningEvent */ (const ff_asf_guid){0xE5,0xC5,0x67,0x90,0x5C,0x4C,0x05,0x42,0x86,0xC8,0x7A,0xFE,0x20,0xFE,0x1E,0xFA}) ||
            !ff_guidcmp(g, /* EVENTID_ChannelInfoSpanningEvent */ (const ff_asf_guid){0x80,0x6D,0xF3,0x41,0x32,0x41,0xC2,0x4C,0xB1,0x21,0x01,0xA4,0x32,0x19,0xD8,0x1B}) ||
            !ff_guidcmp(g, /* EVENTID_ChannelTypeSpanningEvent */ (const ff_asf_guid){0x51,0x1D,0xAB,0x72,0xD2,0x87,0x9B,0x48,0xBA,0x11,0x0E,0x08,0xDC,0x21,0x02,0x43}) ||
            !ff_guidcmp(g, /* EVENTID_PIDListSpanningEvent */ (const ff_asf_guid){0x65,0x8F,0xFC,0x47,0xBB,0xE2,0x34,0x46,0x9C,0xEF,0xFD,0xBF,0xE6,0x26,0x1D,0x5C}) ||
            !ff_guidcmp(g, /* EVENTID_SignalAndServiceStatusSpanningEvent */ (const ff_asf_guid){0xCB,0xC5,0x68,0x80,0x04,0x3C,0x2B,0x49,0xB4,0x7D,0x03,0x08,0x82,0x0D,0xCE,0x51}) ||
            !ff_guidcmp(g, /* EVENTID_StreamTypeSpanningEvent */ (const ff_asf_guid){0xBC,0x2E,0xAF,0x82,0xA6,0x30,0x64,0x42,0xA8,0x0B,0xAD,0x2E,0x13,0x72,0xAC,0x60}) ||
            !ff_guidcmp(g, (const ff_asf_guid){0x1E,0xBE,0xC3,0xC5,0x43,0x92,0xDC,0x11,0x85,0xE5,0x00,0x12,0x3F,0x6F,0x73,0xB9}) ||
            !ff_guidcmp(g, (const ff_asf_guid){0x3B,0x86,0xA2,0xB1,0xEB,0x1E,0xC3,0x44,0x8C,0x88,0x1C,0xA3,0xFF,0xE3,0xE7,0x6A}) ||
            !ff_guidcmp(g, (const ff_asf_guid){0x4E,0x7F,0x4C,0x5B,0xC4,0xD0,0x38,0x4B,0xA8,0x3E,0x21,0x7F,0x7B,0xBF,0x52,0xE7}) ||
            !ff_guidcmp(g, (const ff_asf_guid){0x63,0x36,0xEB,0xFE,0xA1,0x7E,0xD9,0x11,0x83,0x08,0x00,0x07,0xE9,0x5E,0xAD,0x8D}) ||
            !ff_guidcmp(g, (const ff_asf_guid){0x70,0xE9,0xF1,0xF8,0x89,0xA4,0x4C,0x4D,0x83,0x73,0xB8,0x12,0xE0,0xD5,0xF8,0x1E}) ||
            !ff_guidcmp(g, ff_index_guid) ||
            !ff_guidcmp(g, ff_sync_guid) ||
            !ff_guidcmp(g, ff_stream1_guid) ||
            !ff_guidcmp(g, (const ff_asf_guid){0xF7,0x10,0x02,0xB9,0xEE,0x7C,0xED,0x4E,0xBD,0x7F,0x05,0x40,0x35,0x86,0x18,0xA1})) {
            //ignore known guids
        } else
            av_log(s, AV_LOG_WARNING, "unsupported chunk:"FF_PRI_GUID"\n", FF_ARG_GUID(g));
 
        if (avio_feof(pb))
            break;
 
        avio_skip(pb, WTV_PAD8(len) - consumed);
    }
    return AVERROR_EOF;
}
 
static int read_header(AVFormatContext *s)
{
    WtvContext *wtv = s->priv_data;
    unsigned root_sector;
    int root_size;
    uint8_t root[WTV_SECTOR_SIZE];
    AVIOContext *pb;
    int64_t timeline_pos;
    int64_t ret;
 
    wtv->epoch          =
    wtv->pts            =
    wtv->last_valid_pts = AV_NOPTS_VALUE;
 
    /* read root directory sector */
    avio_skip(s->pb, 0x30);
    root_size = avio_rl32(s->pb);
    if (root_size > sizeof(root)) {
        av_log(s, AV_LOG_ERROR, "root directory size exceeds sector size\n");
        return AVERROR_INVALIDDATA;
    }
    avio_skip(s->pb, 4);
    root_sector = avio_rl32(s->pb);
 
    ret = seek_by_sector(s->pb, root_sector, 0);
    if (ret < 0)
        return ret;
    root_size = avio_read(s->pb, root, root_size);
    if (root_size < 0)
        return AVERROR_INVALIDDATA;
 
    /* parse chunks up until first data chunk */
    wtv->pb = wtvfile_open(s, root, root_size, ff_timeline_le16);
    if (!wtv->pb) {
        av_log(s, AV_LOG_ERROR, "timeline data missing\n");
        return AVERROR_INVALIDDATA;
    }
 
    ret = parse_chunks(s, SEEK_TO_DATA, 0, 0);
    if (ret < 0) {
        wtvfile_close(wtv->pb);
        return ret;
    }
    avio_seek(wtv->pb, -32, SEEK_CUR);
 
    timeline_pos = avio_tell(s->pb); // save before opening another file
 
    /* read metadata */
    pb = wtvfile_open(s, root, root_size, ff_table_0_entries_legacy_attrib_le16);
    if (pb) {
        parse_legacy_attrib(s, pb);
        wtvfile_close(pb);
    }
 
    s->ctx_flags |= AVFMTCTX_NOHEADER; // Needed for noStreams.wtv
 
    /* read seek index */
    if (s->nb_streams) {
        AVStream *st = s->streams[0];
        pb = wtvfile_open(s, root, root_size, ff_table_0_entries_time_le16);
        if (pb) {
            while(1) {
                uint64_t timestamp = avio_rl64(pb);
                uint64_t frame_nb  = avio_rl64(pb);
                if (avio_feof(pb))
                    break;
                ff_add_index_entry(&wtv->index_entries, &wtv->nb_index_entries, &wtv->index_entries_allocated_size,
                                   0, timestamp, frame_nb, 0, AVINDEX_KEYFRAME);
            }
            wtvfile_close(pb);
 
            if (wtv->nb_index_entries) {
                pb = wtvfile_open(s, root, root_size, ff_timeline_table_0_entries_Events_le16);
                if (pb) {
                    AVIndexEntry *e = wtv->index_entries;
                    AVIndexEntry *e_end = wtv->index_entries + wtv->nb_index_entries - 1;
                    uint64_t last_position = 0;
                    while (1) {
                        uint64_t frame_nb = avio_rl64(pb);
                        uint64_t position = avio_rl64(pb);
                        while (e <= e_end && frame_nb > e->size) {
                            e->pos = last_position;
                            e++;
                        }
                        if (avio_feof(pb))
                            break;
                        last_position = position;
                    }
                    e_end->pos = last_position;
                    wtvfile_close(pb);
                    st->duration = e_end->timestamp;
                }
            }
        }
    }
 
    avio_seek(s->pb, timeline_pos, SEEK_SET);
    return 0;
}
 
static int read_packet(AVFormatContext *s, AVPacket *pkt)
{
    WtvContext *wtv = s->priv_data;
    AVIOContext *pb = wtv->pb;
    int stream_index, len, ret;
 
    stream_index = parse_chunks(s, SEEK_TO_DATA, 0, &len);
    if (stream_index < 0)
        return stream_index;
 
    ret = av_get_packet(pb, pkt, len - 32);
    if (ret < 0)
        return ret;
    pkt->stream_index = stream_index;
    pkt->pts          = wtv->pts;
    avio_skip(pb, WTV_PAD8(len) - len);
    return 0;
}
 
static int read_seek(AVFormatContext *s, int stream_index,
                     int64_t ts, int flags)
{
    WtvContext *wtv = s->priv_data;
    AVIOContext *pb = wtv->pb;
    AVStream *st = s->streams[0];
    int64_t ts_relative;
    int i;
 
    if ((flags & AVSEEK_FLAG_FRAME) || (flags & AVSEEK_FLAG_BYTE))
        return AVERROR(ENOSYS);
 
    /* timestamp adjustment is required because wtv->pts values are absolute,
     * whereas AVIndexEntry->timestamp values are relative to epoch. */
    ts_relative = ts;
    if (wtv->epoch != AV_NOPTS_VALUE)
        ts_relative -= wtv->epoch;
 
    i = ff_index_search_timestamp(wtv->index_entries, wtv->nb_index_entries, ts_relative, flags);
    if (i < 0) {
        if (wtv->last_valid_pts == AV_NOPTS_VALUE || ts < wtv->last_valid_pts) {
            if (avio_seek(pb, 0, SEEK_SET) < 0)
                return -1;
        } else if (st->duration != AV_NOPTS_VALUE && ts_relative > st->duration && wtv->nb_index_entries) {
            if (avio_seek(pb, wtv->index_entries[wtv->nb_index_entries - 1].pos, SEEK_SET) < 0)
                return -1;
        }
        if (parse_chunks(s, SEEK_TO_PTS, ts, 0) < 0)
            return AVERROR(ERANGE);
        return 0;
    }
    if (avio_seek(pb, wtv->index_entries[i].pos, SEEK_SET) < 0)
        return -1;
    wtv->pts = wtv->index_entries[i].timestamp;
    if (wtv->epoch != AV_NOPTS_VALUE)
        wtv->pts += wtv->epoch;
    wtv->last_valid_pts = wtv->pts;
    return 0;
}
 
static int read_close(AVFormatContext *s)
{
    WtvContext *wtv = s->priv_data;
    av_freep(&wtv->index_entries);
    wtvfile_close(wtv->pb);
    return 0;
}
 
const FFInputFormat ff_wtv_demuxer = {
    .p.name         = "wtv",
    .p.long_name    = NULL_IF_CONFIG_SMALL("Windows Television (WTV)"),
    .p.flags        = AVFMT_SHOW_IDS,
    .priv_data_size = sizeof(WtvContext),
    .read_probe     = read_probe,
    .read_header    = read_header,
    .read_packet    = read_packet,
    .read_seek      = read_seek,
    .read_close     = read_close,
};