/*
 * FLV demuxer
 * Copyright (c) 2003 The Libav Project
 *
 * This demuxer will generate a 1 byte extradata for VP6F content.
 * It is composed of:
 *  - upper 4 bits: difference between encoded width and visible width
 *  - lower 4 bits: difference between encoded height and visible height
 *
 * This file is part of Libav.
 *
 * Libav 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.
 *
 * Libav 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 Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/avstring.h"
#include "libavutil/channel_layout.h"
#include "libavutil/dict.h"
#include "libavutil/opt.h"
#include "libavutil/intfloat.h"
#include "libavutil/mathematics.h"
#include "libavcodec/bytestream.h"
#include "libavcodec/mpeg4audio.h"
#include "avformat.h"
#include "internal.h"
#include "avio_internal.h"
#include "flv.h"

#define KEYFRAMES_TAG            "keyframes"
#define KEYFRAMES_TIMESTAMP_TAG  "times"
#define KEYFRAMES_BYTEOFFSET_TAG "filepositions"

#define VALIDATE_INDEX_TS_THRESH 2500

typedef struct FLVContext {
    const AVClass *class; ///< Class for private options.
    int trust_metadata;   ///< configure streams according onMetaData
    int wrong_dts;        ///< wrong dts due to negative cts
    uint8_t *new_extradata[2];
    int new_extradata_size[2];
    int last_sample_rate;
    int last_channels;
    struct {
        int64_t dts;
        int64_t pos;
    } validate_index[2];
    int validate_next;
    int validate_count;
    int searched_for_end;
} FLVContext;

static int flv_probe(AVProbeData *p)
{
    const uint8_t *d;

    d = p->buf;
    if (d[0] == 'F' &&
        d[1] == 'L' &&
        d[2] == 'V' &&
        d[3] < 5 && d[5] == 0 &&
        AV_RB32(d + 5) > 8) {
        return AVPROBE_SCORE_MAX;
    }
    return 0;
}

static AVStream *create_stream(AVFormatContext *s, int codec_type)
{
    AVStream *st = avformat_new_stream(s, NULL);
    if (!st)
        return NULL;
    st->codecpar->codec_type = codec_type;
    avpriv_set_pts_info(st, 32, 1, 1000); /* 32 bit pts in ms */
    return st;
}

static int flv_same_audio_codec(AVCodecParameters *apar, int flags)
{
    int bits_per_coded_sample = (flags & FLV_AUDIO_SAMPLESIZE_MASK) ? 16 : 8;
    int flv_codecid           = flags & FLV_AUDIO_CODECID_MASK;
    int codec_id;

    if (!apar->codec_id && !apar->codec_tag)
        return 1;

    if (apar->bits_per_coded_sample != bits_per_coded_sample)
        return 0;

    switch (flv_codecid) {
    // no distinction between S16 and S8 PCM codec flags
    case FLV_CODECID_PCM:
        codec_id = bits_per_coded_sample == 8
                   ? AV_CODEC_ID_PCM_U8
#if HAVE_BIGENDIAN
                   : AV_CODEC_ID_PCM_S16BE;
#else
                   : AV_CODEC_ID_PCM_S16LE;
#endif
        return codec_id == apar->codec_id;
    case FLV_CODECID_PCM_LE:
        codec_id = bits_per_coded_sample == 8
                   ? AV_CODEC_ID_PCM_U8
                   : AV_CODEC_ID_PCM_S16LE;
        return codec_id == apar->codec_id;
    case FLV_CODECID_AAC:
        return apar->codec_id == AV_CODEC_ID_AAC;
    case FLV_CODECID_ADPCM:
        return apar->codec_id == AV_CODEC_ID_ADPCM_SWF;
    case FLV_CODECID_SPEEX:
        return apar->codec_id == AV_CODEC_ID_SPEEX;
    case FLV_CODECID_MP3:
        return apar->codec_id == AV_CODEC_ID_MP3;
    case FLV_CODECID_NELLYMOSER_8KHZ_MONO:
    case FLV_CODECID_NELLYMOSER_16KHZ_MONO:
    case FLV_CODECID_NELLYMOSER:
        return apar->codec_id == AV_CODEC_ID_NELLYMOSER;
    case FLV_CODECID_PCM_MULAW:
        return apar->sample_rate == 8000 &&
               apar->codec_id    == AV_CODEC_ID_PCM_MULAW;
    case FLV_CODECID_PCM_ALAW:
        return apar->sample_rate == 8000 &&
               apar->codec_id    == AV_CODEC_ID_PCM_ALAW;
    default:
        return apar->codec_tag == (flv_codecid >> FLV_AUDIO_CODECID_OFFSET);
    }
}

static void flv_set_audio_codec(AVFormatContext *s, AVStream *astream,
                                AVCodecParameters *apar, int flv_codecid)
{
    switch (flv_codecid) {
    // no distinction between S16 and S8 PCM codec flags
    case FLV_CODECID_PCM:
        apar->codec_id = apar->bits_per_coded_sample == 8
                           ? AV_CODEC_ID_PCM_U8
#if HAVE_BIGENDIAN
                           : AV_CODEC_ID_PCM_S16BE;
#else
                           : AV_CODEC_ID_PCM_S16LE;
#endif
        break;
    case FLV_CODECID_PCM_LE:
        apar->codec_id = apar->bits_per_coded_sample == 8
                           ? AV_CODEC_ID_PCM_U8
                           : AV_CODEC_ID_PCM_S16LE;
        break;
    case FLV_CODECID_AAC:
        apar->codec_id = AV_CODEC_ID_AAC;
        break;
    case FLV_CODECID_ADPCM:
        apar->codec_id = AV_CODEC_ID_ADPCM_SWF;
        break;
    case FLV_CODECID_SPEEX:
        apar->codec_id    = AV_CODEC_ID_SPEEX;
        apar->sample_rate = 16000;
        break;
    case FLV_CODECID_MP3:
        apar->codec_id      = AV_CODEC_ID_MP3;
        astream->need_parsing = AVSTREAM_PARSE_FULL;
        break;
    case FLV_CODECID_NELLYMOSER_8KHZ_MONO:
        // in case metadata does not otherwise declare samplerate
        apar->sample_rate = 8000;
        apar->codec_id    = AV_CODEC_ID_NELLYMOSER;
        break;
    case FLV_CODECID_NELLYMOSER_16KHZ_MONO:
        apar->sample_rate = 16000;
        apar->codec_id    = AV_CODEC_ID_NELLYMOSER;
        break;
    case FLV_CODECID_NELLYMOSER:
        apar->codec_id = AV_CODEC_ID_NELLYMOSER;
        break;
    case FLV_CODECID_PCM_MULAW:
        apar->sample_rate = 8000;
        apar->codec_id    = AV_CODEC_ID_PCM_MULAW;
        break;
    case FLV_CODECID_PCM_ALAW:
        apar->sample_rate = 8000;
        apar->codec_id    = AV_CODEC_ID_PCM_ALAW;
        break;
    default:
        av_log(s, AV_LOG_INFO, "Unsupported audio codec (%x)\n",
               flv_codecid >> FLV_AUDIO_CODECID_OFFSET);
        apar->codec_tag = flv_codecid >> FLV_AUDIO_CODECID_OFFSET;
    }
}

static int flv_same_video_codec(AVCodecParameters *vpar, int flags)
{
    int flv_codecid = flags & FLV_VIDEO_CODECID_MASK;

    if (!vpar->codec_id && !vpar->codec_tag)
        return 1;

    switch (flv_codecid) {
    case FLV_CODECID_H263:
        return vpar->codec_id == AV_CODEC_ID_FLV1;
    case FLV_CODECID_SCREEN:
        return vpar->codec_id == AV_CODEC_ID_FLASHSV;
    case FLV_CODECID_SCREEN2:
        return vpar->codec_id == AV_CODEC_ID_FLASHSV2;
    case FLV_CODECID_VP6:
        return vpar->codec_id == AV_CODEC_ID_VP6F;
    case FLV_CODECID_VP6A:
        return vpar->codec_id == AV_CODEC_ID_VP6A;
    case FLV_CODECID_H264:
        return vpar->codec_id == AV_CODEC_ID_H264;
    default:
        return vpar->codec_tag == flv_codecid;
    }
}

static int flv_set_video_codec(AVFormatContext *s, AVStream *vstream,
                               int flv_codecid, int read)
{
    AVCodecParameters *par = vstream->codecpar;
    switch (flv_codecid) {
    case FLV_CODECID_H263:
        par->codec_id = AV_CODEC_ID_FLV1;
        break;
    case FLV_CODECID_SCREEN:
        par->codec_id = AV_CODEC_ID_FLASHSV;
        break;
    case FLV_CODECID_SCREEN2:
        par->codec_id = AV_CODEC_ID_FLASHSV2;
        break;
    case FLV_CODECID_VP6:
        par->codec_id = AV_CODEC_ID_VP6F;
    case FLV_CODECID_VP6A:
        if (flv_codecid == FLV_CODECID_VP6A)
            par->codec_id = AV_CODEC_ID_VP6A;
        if (read) {
            if (par->extradata_size != 1) {
                par->extradata = av_malloc(1);
                if (par->extradata)
                    par->extradata_size = 1;
            }
            if (par->extradata)
                par->extradata[0] = avio_r8(s->pb);
            else
                avio_skip(s->pb, 1);
        }
        return 1;     // 1 byte body size adjustment for flv_read_packet()
    case FLV_CODECID_H264:
        par->codec_id = AV_CODEC_ID_H264;
        return 3;     // not 4, reading packet type will consume one byte
    default:
        av_log(s, AV_LOG_INFO, "Unsupported video codec (%x)\n", flv_codecid);
        par->codec_tag = flv_codecid;
    }

    return 0;
}

static int amf_get_string(AVIOContext *ioc, char *buffer, int buffsize)
{
    int length = avio_rb16(ioc);
    if (length >= buffsize) {
        avio_skip(ioc, length);
        return -1;
    }

    avio_read(ioc, buffer, length);

    buffer[length] = '\0';

    return length;
}

static int parse_keyframes_index(AVFormatContext *s, AVIOContext *ioc,
                                 AVStream *vstream, int64_t max_pos)
{
    FLVContext *flv       = s->priv_data;
    unsigned int arraylen = 0, timeslen = 0, fileposlen = 0, i;
    double num_val;
    char str_val[256];
    int64_t *times         = NULL;
    int64_t *filepositions = NULL;
    int ret                = AVERROR(ENOSYS);
    int64_t initial_pos    = avio_tell(ioc);

    if (s->flags & AVFMT_FLAG_IGNIDX)
        return 0;

    while (avio_tell(ioc) < max_pos - 2 &&
           amf_get_string(ioc, str_val, sizeof(str_val)) > 0) {
        int64_t *current_array;

        // Expect array object in context
        if (avio_r8(ioc) != AMF_DATA_TYPE_ARRAY)
            break;

        arraylen = avio_rb32(ioc);
        if (arraylen >> 28)
            break;

        /* Expect only 'times' or 'filepositions' sub-arrays in other
         * case refuse to use such metadata for indexing. */
        if (!strcmp(KEYFRAMES_TIMESTAMP_TAG, str_val) && !times) {
            if (!(times = av_mallocz(sizeof(*times) * arraylen))) {
                ret = AVERROR(ENOMEM);
                goto finish;
            }
            timeslen      = arraylen;
            current_array = times;
        } else if (!strcmp(KEYFRAMES_BYTEOFFSET_TAG, str_val) &&
                   !filepositions) {
            if (!(filepositions = av_mallocz(sizeof(*filepositions) * arraylen))) {
                ret = AVERROR(ENOMEM);
                goto finish;
            }
            fileposlen    = arraylen;
            current_array = filepositions;
        } else
            // unexpected metatag inside keyframes, will not use such
            // metadata for indexing
            break;

        for (i = 0; i < arraylen && avio_tell(ioc) < max_pos - 1; i++) {
            if (avio_r8(ioc) != AMF_DATA_TYPE_NUMBER)
                goto finish;
            num_val          = av_int2double(avio_rb64(ioc));
            current_array[i] = num_val;
        }
        if (times && filepositions) {
            // All done, exiting at a position allowing amf_parse_object
            // to finish parsing the object
            ret = 0;
            break;
        }
    }

    if (!ret && timeslen == fileposlen) {
        for (i = 0; i < fileposlen; i++) {
            av_add_index_entry(vstream, filepositions[i], times[i] * 1000,
                               0, 0, AVINDEX_KEYFRAME);
            if (i < 2) {
                flv->validate_index[i].pos = filepositions[i];
                flv->validate_index[i].dts = times[i] * 1000;
                flv->validate_count        = i + 1;
            }
        }
    } else
        av_log(s, AV_LOG_WARNING, "Invalid keyframes object, skipping.\n");

finish:
    av_freep(&times);
    av_freep(&filepositions);
    // If we got unexpected data, but successfully reset back to
    // the start pos, the caller can continue parsing
    if (ret < 0 && avio_seek(ioc, initial_pos, SEEK_SET) > 0)
        return 0;
    return ret;
}

static int amf_parse_object(AVFormatContext *s, AVStream *astream,
                            AVStream *vstream, const char *key,
                            int64_t max_pos, int depth)
{
    AVCodecParameters *apar, *vpar;
    FLVContext *flv = s->priv_data;
    AVIOContext *ioc;
    AMFDataType amf_type;
    char str_val[256];
    double num_val;

    num_val  = 0;
    ioc      = s->pb;
    amf_type = avio_r8(ioc);

    switch (amf_type) {
    case AMF_DATA_TYPE_NUMBER:
        num_val = av_int2double(avio_rb64(ioc));
        break;
    case AMF_DATA_TYPE_BOOL:
        num_val = avio_r8(ioc);
        break;
    case AMF_DATA_TYPE_STRING:
        if (amf_get_string(ioc, str_val, sizeof(str_val)) < 0)
            return -1;
        break;
    case AMF_DATA_TYPE_OBJECT:
        if ((vstream || astream) && key &&
            !strcmp(KEYFRAMES_TAG, key) && depth == 1)
            if (parse_keyframes_index(s, ioc, vstream ? vstream : astream,
                                      max_pos) < 0)
                return -1;

        while (avio_tell(ioc) < max_pos - 2 &&
               amf_get_string(ioc, str_val, sizeof(str_val)) > 0)
            if (amf_parse_object(s, astream, vstream, str_val, max_pos,
                                 depth + 1) < 0)
                return -1;     // if we couldn't skip, bomb out.
        if (avio_r8(ioc) != AMF_END_OF_OBJECT)
            return -1;
        break;
    case AMF_DATA_TYPE_NULL:
    case AMF_DATA_TYPE_UNDEFINED:
    case AMF_DATA_TYPE_UNSUPPORTED:
        break;     // these take up no additional space
    case AMF_DATA_TYPE_MIXEDARRAY:
        avio_skip(ioc, 4);     // skip 32-bit max array index
        while (avio_tell(ioc) < max_pos - 2 &&
               amf_get_string(ioc, str_val, sizeof(str_val)) > 0)
            // this is the only case in which we would want a nested
            // parse to not skip over the object
            if (amf_parse_object(s, astream, vstream, str_val, max_pos,
                                 depth + 1) < 0)
                return -1;
        if (avio_r8(ioc) != AMF_END_OF_OBJECT)
            return -1;
        break;
    case AMF_DATA_TYPE_ARRAY:
    {
        unsigned int arraylen, i;

        arraylen = avio_rb32(ioc);
        for (i = 0; i < arraylen && avio_tell(ioc) < max_pos - 1; i++)
            if (amf_parse_object(s, NULL, NULL, NULL, max_pos,
                                 depth + 1) < 0)
                return -1;      // if we couldn't skip, bomb out.
    }
    break;
    case AMF_DATA_TYPE_DATE:
        avio_skip(ioc, 8 + 2);  // timestamp (double) and UTC offset (int16)
        break;
    default:                    // unsupported type, we couldn't skip
        return -1;
    }

    if (key) {
        // stream info doesn't live any deeper than the first object
        if (depth == 1) {
            apar = astream ? astream->codecpar : NULL;
            vpar = vstream ? vstream->codecpar : NULL;

            if (amf_type == AMF_DATA_TYPE_NUMBER ||
                amf_type == AMF_DATA_TYPE_BOOL) {
                if (!strcmp(key, "duration"))
                    s->duration = num_val * AV_TIME_BASE;
                else if (!strcmp(key, "videodatarate") && vpar &&
                         0 <= (int)(num_val * 1024.0))
                    vpar->bit_rate = num_val * 1024.0;
                else if (!strcmp(key, "audiodatarate") && apar &&
                         0 <= (int)(num_val * 1024.0))
                    apar->bit_rate = num_val * 1024.0;
                else if (!strcmp(key, "datastream")) {
                    AVStream *st = create_stream(s, AVMEDIA_TYPE_DATA);
                    if (!st)
                        return AVERROR(ENOMEM);
                    st->codecpar->codec_id = AV_CODEC_ID_TEXT;
                } else if (flv->trust_metadata) {
                    if (!strcmp(key, "videocodecid") && vpar) {
                        flv_set_video_codec(s, vstream, num_val, 0);
                    } else if (!strcmp(key, "audiocodecid") && apar) {
                        int id = ((int)num_val) << FLV_AUDIO_CODECID_OFFSET;
                        flv_set_audio_codec(s, astream, apar, id);
                    } else if (!strcmp(key, "audiosamplerate") && apar) {
                        apar->sample_rate = num_val;
                    } else if (!strcmp(key, "audiosamplesize") && apar) {
                        apar->bits_per_coded_sample = num_val;
                    } else if (!strcmp(key, "stereo") && apar) {
                        apar->channels       = num_val + 1;
                        apar->channel_layout = apar->channels == 2 ?
                                               AV_CH_LAYOUT_STEREO :
                                               AV_CH_LAYOUT_MONO;
                    } else if (!strcmp(key, "width") && vpar) {
                        vpar->width = num_val;
                    } else if (!strcmp(key, "height") && vpar) {
                        vpar->height = num_val;
                    }
                }
            }
        }

        if (!strcmp(key, "duration")        ||
            !strcmp(key, "filesize")        ||
            !strcmp(key, "width")           ||
            !strcmp(key, "height")          ||
            !strcmp(key, "videodatarate")   ||
            !strcmp(key, "framerate")       ||
            !strcmp(key, "videocodecid")    ||
            !strcmp(key, "audiodatarate")   ||
            !strcmp(key, "audiosamplerate") ||
            !strcmp(key, "audiosamplesize") ||
            !strcmp(key, "stereo")          ||
            !strcmp(key, "audiocodecid")    ||
            !strcmp(key, "datastream"))
            return 0;

        s->event_flags |= AVFMT_EVENT_FLAG_METADATA_UPDATED;
        if (amf_type == AMF_DATA_TYPE_BOOL) {
            av_strlcpy(str_val, num_val > 0 ? "true" : "false",
                       sizeof(str_val));
            av_dict_set(&s->metadata, key, str_val, 0);
        } else if (amf_type == AMF_DATA_TYPE_NUMBER) {
            snprintf(str_val, sizeof(str_val), "%.f", num_val);
            av_dict_set(&s->metadata, key, str_val, 0);
        } else if (amf_type == AMF_DATA_TYPE_STRING)
            av_dict_set(&s->metadata, key, str_val, 0);
    }

    return 0;
}

static int flv_read_metabody(AVFormatContext *s, int64_t next_pos)
{
    AMFDataType type;
    AVStream *stream, *astream, *vstream;
    AVIOContext *ioc;
    int i;
    // only needs to hold the string "onMetaData".
    // Anything longer is something we don't want.
    char buffer[11];

    astream = NULL;
    vstream = NULL;
    ioc     = s->pb;

    // first object needs to be "onMetaData" string
    type = avio_r8(ioc);
    if (type != AMF_DATA_TYPE_STRING ||
        amf_get_string(ioc, buffer, sizeof(buffer)) < 0)
        return -1;

    if (!strcmp(buffer, "onTextData"))
        return 1;

    if (strcmp(buffer, "onMetaData") && strcmp(buffer, "onCuePoint"))
        return -1;

    // find the streams now so that amf_parse_object doesn't need to do
    // the lookup every time it is called.
    for (i = 0; i < s->nb_streams; i++) {
        stream = s->streams[i];
        if (stream->codecpar->codec_type == AVMEDIA_TYPE_AUDIO)
            astream = stream;
        else if (stream->codecpar->codec_type == AVMEDIA_TYPE_VIDEO)
            vstream = stream;
    }

    // parse the second object (we want a mixed array)
    if (amf_parse_object(s, astream, vstream, buffer, next_pos, 0) < 0)
        return -1;

    return 0;
}

static int flv_read_header(AVFormatContext *s)
{
    int offset;

    avio_skip(s->pb, 4);
    avio_r8(s->pb); // flags

    s->ctx_flags |= AVFMTCTX_NOHEADER;

    offset = avio_rb32(s->pb);
    avio_seek(s->pb, offset, SEEK_SET);
    avio_skip(s->pb, 4);

    s->start_time = 0;

    return 0;
}

static int flv_read_close(AVFormatContext *s)
{
    FLVContext *flv = s->priv_data;
    av_freep(&flv->new_extradata[0]);
    av_freep(&flv->new_extradata[1]);
    return 0;
}

static int flv_get_extradata(AVFormatContext *s, AVStream *st, int size)
{
    av_free(st->codecpar->extradata);
    st->codecpar->extradata = av_mallocz(size + AV_INPUT_BUFFER_PADDING_SIZE);
    if (!st->codecpar->extradata)
        return AVERROR(ENOMEM);
    st->codecpar->extradata_size = size;
    avio_read(s->pb, st->codecpar->extradata, st->codecpar->extradata_size);
    return 0;
}

static int flv_queue_extradata(FLVContext *flv, AVIOContext *pb, int stream,
                               int size)
{
    av_free(flv->new_extradata[stream]);
    flv->new_extradata[stream] = av_mallocz(size +
                                            AV_INPUT_BUFFER_PADDING_SIZE);
    if (!flv->new_extradata[stream])
        return AVERROR(ENOMEM);
    flv->new_extradata_size[stream] = size;
    avio_read(pb, flv->new_extradata[stream], size);
    return 0;
}

static void clear_index_entries(AVFormatContext *s, int64_t pos)
{
    int i, j, out;
    av_log(s, AV_LOG_WARNING,
           "Found invalid index entries, clearing the index.\n");
    for (i = 0; i < s->nb_streams; i++) {
        AVStream *st = s->streams[i];
        /* Remove all index entries that point to >= pos */
        out = 0;
        for (j = 0; j < st->nb_index_entries; j++)
            if (st->index_entries[j].pos < pos)
                st->index_entries[out++] = st->index_entries[j];
        st->nb_index_entries = out;
    }
}

static int amf_skip_tag(AVIOContext *pb, AMFDataType type)
{
    int nb = -1, ret, parse_name = 1;

    switch (type) {
    case AMF_DATA_TYPE_NUMBER:
        avio_skip(pb, 8);
        break;
    case AMF_DATA_TYPE_BOOL:
        avio_skip(pb, 1);
        break;
    case AMF_DATA_TYPE_STRING:
        avio_skip(pb, avio_rb16(pb));
        break;
    case AMF_DATA_TYPE_ARRAY:
        parse_name = 0;
    case AMF_DATA_TYPE_MIXEDARRAY:
        nb = avio_rb32(pb);
    case AMF_DATA_TYPE_OBJECT:
        while(!pb->eof_reached && (nb-- > 0 || type != AMF_DATA_TYPE_ARRAY)) {
            if (parse_name) {
                int size = avio_rb16(pb);
                if (!size) {
                    avio_skip(pb, 1);
                    break;
                }
                avio_skip(pb, size);
            }
            if ((ret = amf_skip_tag(pb, avio_r8(pb))) < 0)
                return ret;
        }
        break;
    case AMF_DATA_TYPE_NULL:
    case AMF_DATA_TYPE_OBJECT_END:
        break;
    default:
        return AVERROR_INVALIDDATA;
    }
    return 0;
}

static int flv_data_packet(AVFormatContext *s, AVPacket *pkt,
                           int64_t dts, int64_t next)
{
    AVIOContext *pb = s->pb;
    AVStream *st    = NULL;
    char buf[20];
    int ret = AVERROR_INVALIDDATA;
    int i, length = -1;

    switch (avio_r8(pb)) {
    case AMF_DATA_TYPE_MIXEDARRAY:
        avio_seek(pb, 4, SEEK_CUR);
    case AMF_DATA_TYPE_OBJECT:
        break;
    default:
        goto skip;
    }

    while ((ret = amf_get_string(pb, buf, sizeof(buf))) > 0) {
        AMFDataType type = avio_r8(pb);
        if (type == AMF_DATA_TYPE_STRING && !strcmp(buf, "text")) {
            length = avio_rb16(pb);
            ret    = av_get_packet(pb, pkt, length);
            if (ret < 0)
                goto skip;
            else
                break;
        } else {
            if ((ret = amf_skip_tag(pb, type)) < 0)
                goto skip;
        }
    }

    if (length < 0) {
        ret = AVERROR_INVALIDDATA;
        goto skip;
    }

    for (i = 0; i < s->nb_streams; i++) {
        st = s->streams[i];
        if (st->codecpar->codec_type == AVMEDIA_TYPE_DATA)
            break;
    }

    if (i == s->nb_streams) {
        st = create_stream(s, AVMEDIA_TYPE_DATA);
        if (!st)
            return AVERROR(ENOMEM);
        st->codecpar->codec_id = AV_CODEC_ID_TEXT;
    }

    pkt->dts  = dts;
    pkt->pts  = dts;
    pkt->size = ret;

    pkt->stream_index = st->index;
    pkt->flags       |= AV_PKT_FLAG_KEY;

skip:
    avio_seek(s->pb, next + 4, SEEK_SET);

    return ret;
}

static int flv_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    FLVContext *flv = s->priv_data;
    int ret, i, size, flags, is_audio;
    enum FlvTagType type;
    int64_t next, pos;
    int64_t dts, pts = AV_NOPTS_VALUE;
    int sample_rate = 0, channels = 0;
    AVStream *st    = NULL;

    /* pkt size is repeated at end. skip it */
    for (;; avio_skip(s->pb, 4)) {
        pos  = avio_tell(s->pb);
        type = avio_r8(s->pb);
        size = avio_rb24(s->pb);
        dts  = avio_rb24(s->pb);
        dts |= avio_r8(s->pb) << 24;
        av_log(s, AV_LOG_TRACE, "type:%d, size:%d, dts:%"PRId64"\n", type, size, dts);
        if (s->pb->eof_reached)
            return AVERROR_EOF;
        avio_skip(s->pb, 3); /* stream id, always 0 */
        flags = 0;

        if (flv->validate_next < flv->validate_count) {
            int64_t validate_pos = flv->validate_index[flv->validate_next].pos;
            if (pos == validate_pos) {
                if (FFABS(dts - flv->validate_index[flv->validate_next].dts) <=
                    VALIDATE_INDEX_TS_THRESH) {
                    flv->validate_next++;
                } else {
                    clear_index_entries(s, validate_pos);
                    flv->validate_count = 0;
                }
            } else if (pos > validate_pos) {
                clear_index_entries(s, validate_pos);
                flv->validate_count = 0;
            }
        }

        if (size == 0)
            continue;

        next = size + avio_tell(s->pb);

        if (type == FLV_TAG_TYPE_AUDIO) {
            is_audio = 1;
            flags    = avio_r8(s->pb);
            size--;
        } else if (type == FLV_TAG_TYPE_VIDEO) {
            is_audio = 0;
            flags    = avio_r8(s->pb);
            size--;
            if ((flags & 0xf0) == 0x50) /* video info / command frame */
                goto skip;
        } else {
            if (type == FLV_TAG_TYPE_META && size > 13 + 1 + 4)
                if (flv_read_metabody(s, next) > 0) {
                    return flv_data_packet(s, pkt, dts, next);
                } else /* skip packet */
                    av_log(s, AV_LOG_DEBUG,
                           "Skipping flv packet: type %d, size %d, flags %d.\n",
                           type, size, flags);

skip:
            avio_seek(s->pb, next, SEEK_SET);
            continue;
        }

        /* skip empty data packets */
        if (!size)
            continue;

        /* now find stream */
        for (i = 0; i < s->nb_streams; i++) {
            st = s->streams[i];
            if (is_audio && st->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
                if (flv_same_audio_codec(st->codecpar, flags))
                    break;
            } else if (!is_audio &&
                       st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
                if (flv_same_video_codec(st->codecpar, flags))
                    break;
            }
        }
        if (i == s->nb_streams) {
            st = create_stream(s, is_audio ? AVMEDIA_TYPE_AUDIO
                                           : AVMEDIA_TYPE_VIDEO);
            if (!st)
                return AVERROR(ENOMEM);
        }
        av_log(s, AV_LOG_TRACE, "%d %X %d \n", is_audio, flags, st->discard);

        if ((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_KEY ||
            is_audio)
            av_add_index_entry(st, pos, dts, size, 0, AVINDEX_KEYFRAME);

        if ((st->discard >= AVDISCARD_NONKEY &&
             !((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_KEY || is_audio)) ||
            (st->discard >= AVDISCARD_BIDIR &&
             ((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_DISP_INTER && !is_audio)) ||
            st->discard >= AVDISCARD_ALL) {
            avio_seek(s->pb, next, SEEK_SET);
            continue;
        }
        break;
    }

    // if not streamed and no duration from metadata then seek to end to find
    // the duration from the timestamps
    if (s->pb->seekable && (!s->duration || s->duration == AV_NOPTS_VALUE) &&
        !flv->searched_for_end) {
        int size;
        const int64_t pos   = avio_tell(s->pb);
        // Read the last 4 bytes of the file, this should be the size of the
        // previous FLV tag. Use the timestamp of its payload as duration.
        const int64_t fsize = avio_size(s->pb);
        avio_seek(s->pb, fsize - 4, SEEK_SET);
        size = avio_rb32(s->pb);
        if (size > 0 && size < fsize) {
            // Seek to the start of the last FLV tag at position (fsize - 4 - size)
            // but skip the byte indicating the type.
            avio_seek(s->pb, fsize - 3 - size, SEEK_SET);
            if (size == avio_rb24(s->pb) + 11) {
                uint32_t ts = avio_rb24(s->pb);
                ts         |= avio_r8(s->pb) << 24;
                s->duration = ts * (int64_t)AV_TIME_BASE / 1000;
            }
        }
        avio_seek(s->pb, pos, SEEK_SET);
        flv->searched_for_end = 1;
    }

    if (is_audio) {
        int bits_per_coded_sample;
        channels = (flags & FLV_AUDIO_CHANNEL_MASK) == FLV_STEREO ? 2 : 1;
        sample_rate = 44100 << ((flags & FLV_AUDIO_SAMPLERATE_MASK) >>
                                FLV_AUDIO_SAMPLERATE_OFFSET) >> 3;
        bits_per_coded_sample = (flags & FLV_AUDIO_SAMPLESIZE_MASK) ? 16 : 8;
        if (!st->codecpar->channels || !st->codecpar->sample_rate ||
            !st->codecpar->bits_per_coded_sample) {
            st->codecpar->channels              = channels;
            st->codecpar->channel_layout        = channels == 1
                                               ? AV_CH_LAYOUT_MONO
                                               : AV_CH_LAYOUT_STEREO;
            st->codecpar->sample_rate           = sample_rate;
            st->codecpar->bits_per_coded_sample = bits_per_coded_sample;
        }
        if (!st->codecpar->codec_id) {
            flv_set_audio_codec(s, st, st->codecpar,
                                flags & FLV_AUDIO_CODECID_MASK);
            flv->last_sample_rate =
            sample_rate           = st->codecpar->sample_rate;
            flv->last_channels    =
            channels              = st->codecpar->channels;
        } else {
            AVCodecParameters *par = avcodec_parameters_alloc();
            if (!par) {
                ret = AVERROR(ENOMEM);
                goto leave;
            }
            par->sample_rate = sample_rate;
            par->bits_per_coded_sample = bits_per_coded_sample;
            flv_set_audio_codec(s, st, par, flags & FLV_AUDIO_CODECID_MASK);
            sample_rate = par->sample_rate;
            avcodec_parameters_free(&par);
        }
    } else {
        size -= flv_set_video_codec(s, st, flags & FLV_VIDEO_CODECID_MASK, 1);
    }

    if (st->codecpar->codec_id == AV_CODEC_ID_AAC ||
        st->codecpar->codec_id == AV_CODEC_ID_H264) {
        int type = avio_r8(s->pb);
        size--;
        if (st->codecpar->codec_id == AV_CODEC_ID_H264) {
            // sign extension
            int32_t cts = (avio_rb24(s->pb) + 0xff800000) ^ 0xff800000;
            pts = dts + cts;
            if (cts < 0 && !flv->wrong_dts) { // dts might be wrong
                flv->wrong_dts = 1;
                av_log(s, AV_LOG_WARNING,
                       "Negative cts, previous timestamps might be wrong.\n");
            }
        }
        if (type == 0) {
            if (st->codecpar->extradata) {
                if ((ret = flv_queue_extradata(flv, s->pb, is_audio, size)) < 0)
                    return ret;
                ret = AVERROR(EAGAIN);
                goto leave;
            }
            if ((ret = flv_get_extradata(s, st, size)) < 0)
                return ret;
            if (st->codecpar->codec_id == AV_CODEC_ID_AAC) {
                MPEG4AudioConfig cfg;

                /* Workaround for buggy Omnia A/XE encoder */
                AVDictionaryEntry *t = av_dict_get(s->metadata, "Encoder", NULL, 0);
                if (t && !strcmp(t->value, "Omnia A/XE"))
                    st->codecpar->extradata_size = 2;

                avpriv_mpeg4audio_get_config(&cfg, st->codecpar->extradata,
                                             st->codecpar->extradata_size * 8, 1);
                st->codecpar->channels       = cfg.channels;
                st->codecpar->channel_layout = 0;
                if (cfg.ext_sample_rate)
                    st->codecpar->sample_rate = cfg.ext_sample_rate;
                else
                    st->codecpar->sample_rate = cfg.sample_rate;
                av_log(s, AV_LOG_TRACE, "mp4a config channels %d sample rate %d\n",
                       st->codecpar->channels, st->codecpar->sample_rate);
            }

            ret = AVERROR(EAGAIN);
            goto leave;
        }
    }

    /* skip empty data packets */
    if (!size) {
        ret = AVERROR(EAGAIN);
        goto leave;
    }

    ret = av_get_packet(s->pb, pkt, size);
    if (ret < 0)
        return AVERROR(EIO);
    /* note: we need to modify the packet size here to handle the last
     * packet */
    pkt->size         = ret;
    pkt->dts          = dts;
    pkt->pts          = pts == AV_NOPTS_VALUE ? dts : pts;
    pkt->stream_index = st->index;
    if (flv->new_extradata[is_audio]) {
        uint8_t *side = av_packet_new_side_data(pkt, AV_PKT_DATA_NEW_EXTRADATA,
                                                flv->new_extradata_size[is_audio]);
        if (side) {
            memcpy(side, flv->new_extradata[is_audio],
                   flv->new_extradata_size[is_audio]);
            av_freep(&flv->new_extradata[is_audio]);
            flv->new_extradata_size[is_audio] = 0;
        }
    }
    if (is_audio && (sample_rate != flv->last_sample_rate ||
                     channels    != flv->last_channels)) {
        flv->last_sample_rate = sample_rate;
        flv->last_channels    = channels;
        ff_add_param_change(pkt, channels, 0, sample_rate, 0, 0);
    }

    if (is_audio || ((flags & FLV_VIDEO_FRAMETYPE_MASK) == FLV_FRAME_KEY))
        pkt->flags |= AV_PKT_FLAG_KEY;

leave:
    avio_skip(s->pb, 4);
    return ret;
}

static int flv_read_seek(AVFormatContext *s, int stream_index,
                         int64_t ts, int flags)
{
    FLVContext *flv = s->priv_data;
    flv->validate_count = 0;
    return avio_seek_time(s->pb, stream_index, ts, flags);
}

#define OFFSET(x) offsetof(FLVContext, x)
#define VD AV_OPT_FLAG_VIDEO_PARAM | AV_OPT_FLAG_DECODING_PARAM
static const AVOption options[] = {
    { "flv_metadata", "Allocate streams according to the onMetaData array", OFFSET(trust_metadata), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, VD },
    { NULL }
};

static const AVClass class = {
    .class_name = "flvdec",
    .item_name  = av_default_item_name,
    .option     = options,
    .version    = LIBAVUTIL_VERSION_INT,
};

AVInputFormat ff_flv_demuxer = {
    .name           = "flv",
    .long_name      = NULL_IF_CONFIG_SMALL("FLV (Flash Video)"),
    .priv_data_size = sizeof(FLVContext),
    .read_probe     = flv_probe,
    .read_header    = flv_read_header,
    .read_packet    = flv_read_packet,
    .read_seek      = flv_read_seek,
    .read_close     = flv_read_close,
    .extensions     = "flv",
    .priv_class     = &class,
};