utils.c

/*
 * various utility functions for use within FFmpeg
 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
 *
 * 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 "avformat.h"
#include "internal.h"
#include "libavcodec/opt.h"
#include "libavcodec/metadata.h"
#include "libavutil/avstring.h"
#include "riff.h"
#include <sys/time.h>
#include <time.h>
#include <strings.h>

#undef NDEBUG
#include <assert.h>

/**
 * @file libavformat/utils.c
 * various utility functions for use within FFmpeg
 */

unsigned avformat_version(void)
{
    return LIBAVFORMAT_VERSION_INT;
}

/* fraction handling */

/**
 * f = val + (num / den) + 0.5.
 *
 * 'num' is normalized so that it is such as 0 <= num < den.
 *
 * @param f fractional number
 * @param val integer value
 * @param num must be >= 0
 * @param den must be >= 1
 */
static void av_frac_init(AVFrac *f, int64_t val, int64_t num, int64_t den)
{
    num += (den >> 1);
    if (num >= den) {
        val += num / den;
        num = num % den;
    }
    f->val = val;
    f->num = num;
    f->den = den;
}

/**
 * Fractional addition to f: f = f + (incr / f->den).
 *
 * @param f fractional number
 * @param incr increment, can be positive or negative
 */
static void av_frac_add(AVFrac *f, int64_t incr)
{
    int64_t num, den;

    num = f->num + incr;
    den = f->den;
    if (num < 0) {
        f->val += num / den;
        num = num % den;
        if (num < 0) {
            num += den;
            f->val--;
        }
    } else if (num >= den) {
        f->val += num / den;
        num = num % den;
    }
    f->num = num;
}

/** head of registered input format linked list */
AVInputFormat *first_iformat = NULL;
/** head of registered output format linked list */
AVOutputFormat *first_oformat = NULL;

AVInputFormat  *av_iformat_next(AVInputFormat  *f)
{
    if(f) return f->next;
    else  return first_iformat;
}

AVOutputFormat *av_oformat_next(AVOutputFormat *f)
{
    if(f) return f->next;
    else  return first_oformat;
}

void av_register_input_format(AVInputFormat *format)
{
    AVInputFormat **p;
    p = &first_iformat;
    while (*p != NULL) p = &(*p)->next;
    *p = format;
    format->next = NULL;
}

void av_register_output_format(AVOutputFormat *format)
{
    AVOutputFormat **p;
    p = &first_oformat;
    while (*p != NULL) p = &(*p)->next;
    *p = format;
    format->next = NULL;
}

int match_ext(const char *filename, const char *extensions)
{
    const char *ext, *p;
    char ext1[32], *q;

    if(!filename)
        return 0;

    ext = strrchr(filename, '.');
    if (ext) {
        ext++;
        p = extensions;
        for(;;) {
            q = ext1;
            while (*p != '\0' && *p != ',' && q-ext1<sizeof(ext1)-1)
                *q++ = *p++;
            *q = '\0';
            if (!strcasecmp(ext1, ext))
                return 1;
            if (*p == '\0')
                break;
            p++;
        }
    }
    return 0;
}

AVOutputFormat *guess_format(const char *short_name, const char *filename,
                             const char *mime_type)
{
    AVOutputFormat *fmt, *fmt_found;
    int score_max, score;

    /* specific test for image sequences */
#ifdef CONFIG_IMAGE2_MUXER
    if (!short_name && filename &&
        av_filename_number_test(filename) &&
        av_guess_image2_codec(filename) != CODEC_ID_NONE) {
        return guess_format("image2", NULL, NULL);
    }
#endif
    /* Find the proper file type. */
    fmt_found = NULL;
    score_max = 0;
    fmt = first_oformat;
    while (fmt != NULL) {
        score = 0;
        if (fmt->name && short_name && !strcmp(fmt->name, short_name))
            score += 100;
        if (fmt->mime_type && mime_type && !strcmp(fmt->mime_type, mime_type))
            score += 10;
        if (filename && fmt->extensions &&
            match_ext(filename, fmt->extensions)) {
            score += 5;
        }
        if (score > score_max) {
            score_max = score;
            fmt_found = fmt;
        }
        fmt = fmt->next;
    }
    return fmt_found;
}

AVOutputFormat *guess_stream_format(const char *short_name, const char *filename,
                             const char *mime_type)
{
    AVOutputFormat *fmt = guess_format(short_name, filename, mime_type);

    if (fmt) {
        AVOutputFormat *stream_fmt;
        char stream_format_name[64];

        snprintf(stream_format_name, sizeof(stream_format_name), "%s_stream", fmt->name);
        stream_fmt = guess_format(stream_format_name, NULL, NULL);

        if (stream_fmt)
            fmt = stream_fmt;
    }

    return fmt;
}

enum CodecID av_guess_codec(AVOutputFormat *fmt, const char *short_name,
                            const char *filename, const char *mime_type, enum CodecType type){
    if(type == CODEC_TYPE_VIDEO){
        enum CodecID codec_id= CODEC_ID_NONE;

#ifdef CONFIG_IMAGE2_MUXER
        if(!strcmp(fmt->name, "image2") || !strcmp(fmt->name, "image2pipe")){
            codec_id= av_guess_image2_codec(filename);
        }
#endif
        if(codec_id == CODEC_ID_NONE)
            codec_id= fmt->video_codec;
        return codec_id;
    }else if(type == CODEC_TYPE_AUDIO)
        return fmt->audio_codec;
    else
        return CODEC_ID_NONE;
}

AVInputFormat *av_find_input_format(const char *short_name)
{
    AVInputFormat *fmt;
    for(fmt = first_iformat; fmt != NULL; fmt = fmt->next) {
        if (!strcmp(fmt->name, short_name))
            return fmt;
    }
    return NULL;
}

/* memory handling */

void av_destruct_packet(AVPacket *pkt)
{
    av_free(pkt->data);
    pkt->data = NULL; pkt->size = 0;
}

void av_init_packet(AVPacket *pkt)
{
    pkt->pts   = AV_NOPTS_VALUE;
    pkt->dts   = AV_NOPTS_VALUE;
    pkt->pos   = -1;
    pkt->duration = 0;
    pkt->convergence_duration = 0;
    pkt->flags = 0;
    pkt->stream_index = 0;
    pkt->destruct= av_destruct_packet_nofree;
}

int av_new_packet(AVPacket *pkt, int size)
{
    uint8_t *data;
    if((unsigned)size > (unsigned)size + FF_INPUT_BUFFER_PADDING_SIZE)
        return AVERROR(ENOMEM);
    data = av_malloc(size + FF_INPUT_BUFFER_PADDING_SIZE);
    if (!data)
        return AVERROR(ENOMEM);
    memset(data + size, 0, FF_INPUT_BUFFER_PADDING_SIZE);

    av_init_packet(pkt);
    pkt->data = data;
    pkt->size = size;
    pkt->destruct = av_destruct_packet;
    return 0;
}

int av_get_packet(ByteIOContext *s, AVPacket *pkt, int size)
{
    int ret= av_new_packet(pkt, size);

    if(ret<0)
        return ret;

    pkt->pos= url_ftell(s);

    ret= get_buffer(s, pkt->data, size);
    if(ret<=0)
        av_free_packet(pkt);
    else
        pkt->size= ret;

    return ret;
}

int av_dup_packet(AVPacket *pkt)
{
    if (pkt->destruct != av_destruct_packet) {
        uint8_t *data;
        /* We duplicate the packet and don't forget to add the padding again. */
        if((unsigned)pkt->size > (unsigned)pkt->size + FF_INPUT_BUFFER_PADDING_SIZE)
            return AVERROR(ENOMEM);
        data = av_malloc(pkt->size + FF_INPUT_BUFFER_PADDING_SIZE);
        if (!data) {
            return AVERROR(ENOMEM);
        }
        memcpy(data, pkt->data, pkt->size);
        memset(data + pkt->size, 0, FF_INPUT_BUFFER_PADDING_SIZE);
        pkt->data = data;
        pkt->destruct = av_destruct_packet;
    }
    return 0;
}

int av_filename_number_test(const char *filename)
{
    char buf[1024];
    return filename && (av_get_frame_filename(buf, sizeof(buf), filename, 1)>=0);
}

static AVInputFormat *av_probe_input_format2(AVProbeData *pd, int is_opened, int *score_max)
{
    AVInputFormat *fmt1, *fmt;
    int score;

    fmt = NULL;
    for(fmt1 = first_iformat; fmt1 != NULL; fmt1 = fmt1->next) {
        if (!is_opened == !(fmt1->flags & AVFMT_NOFILE))
            continue;
        score = 0;
        if (fmt1->read_probe) {
            score = fmt1->read_probe(pd);
        } else if (fmt1->extensions) {
            if (match_ext(pd->filename, fmt1->extensions)) {
                score = 50;
            }
        }
        if (score > *score_max) {
            *score_max = score;
            fmt = fmt1;
        }else if (score == *score_max)
            fmt = NULL;
    }
    return fmt;
}

AVInputFormat *av_probe_input_format(AVProbeData *pd, int is_opened){
    int score=0;
    return av_probe_input_format2(pd, is_opened, &score);
}

static int set_codec_from_probe_data(AVStream *st, AVProbeData *pd, int score)
{
    AVInputFormat *fmt;
    fmt = av_probe_input_format2(pd, 1, &score);

    if (fmt) {
        if (!strcmp(fmt->name, "mp3")) {
            st->codec->codec_id = CODEC_ID_MP3;
            st->codec->codec_type = CODEC_TYPE_AUDIO;
        } else if (!strcmp(fmt->name, "ac3")) {
            st->codec->codec_id = CODEC_ID_AC3;
            st->codec->codec_type = CODEC_TYPE_AUDIO;
        } else if (!strcmp(fmt->name, "mpegvideo")) {
            st->codec->codec_id = CODEC_ID_MPEG2VIDEO;
            st->codec->codec_type = CODEC_TYPE_VIDEO;
        } else if (!strcmp(fmt->name, "m4v")) {
            st->codec->codec_id = CODEC_ID_MPEG4;
            st->codec->codec_type = CODEC_TYPE_VIDEO;
        } else if (!strcmp(fmt->name, "h264")) {
            st->codec->codec_id = CODEC_ID_H264;
            st->codec->codec_type = CODEC_TYPE_VIDEO;
        }
    }
    return !!fmt;
}

/************************************************************/
/* input media file */

/**
 * Open a media file from an IO stream. 'fmt' must be specified.
 */
static const char* format_to_name(void* ptr)
{
    AVFormatContext* fc = (AVFormatContext*) ptr;
    if(fc->iformat) return fc->iformat->name;
    else if(fc->oformat) return fc->oformat->name;
    else return "NULL";
}

#define OFFSET(x) offsetof(AVFormatContext,x)
#define DEFAULT 0 //should be NAN but it does not work as it is not a constant in glibc as required by ANSI/ISO C
//these names are too long to be readable
#define E AV_OPT_FLAG_ENCODING_PARAM
#define D AV_OPT_FLAG_DECODING_PARAM

static const AVOption options[]={
{"probesize", NULL, OFFSET(probesize), FF_OPT_TYPE_INT, 32000, 32, INT_MAX, D}, /* 32000 from mpegts.c: 1.0 second at 24Mbit/s */
{"muxrate", "set mux rate", OFFSET(mux_rate), FF_OPT_TYPE_INT, DEFAULT, 0, INT_MAX, E},
{"packetsize", "set packet size", OFFSET(packet_size), FF_OPT_TYPE_INT, DEFAULT, 0, INT_MAX, E},
{"fflags", NULL, OFFSET(flags), FF_OPT_TYPE_FLAGS, DEFAULT, INT_MIN, INT_MAX, D|E, "fflags"},
{"ignidx", "ignore index", 0, FF_OPT_TYPE_CONST, AVFMT_FLAG_IGNIDX, INT_MIN, INT_MAX, D, "fflags"},
{"genpts", "generate pts", 0, FF_OPT_TYPE_CONST, AVFMT_FLAG_GENPTS, INT_MIN, INT_MAX, D, "fflags"},
{"track", " set the track number", OFFSET(track), FF_OPT_TYPE_INT, DEFAULT, 0, INT_MAX, E},
{"year", "set the year", OFFSET(year), FF_OPT_TYPE_INT, DEFAULT, INT_MIN, INT_MAX, E},
{"analyzeduration", "how many microseconds are analyzed to estimate duration", OFFSET(max_analyze_duration), FF_OPT_TYPE_INT, 3*AV_TIME_BASE, 0, INT_MAX, D},
{"cryptokey", "decryption key", OFFSET(key), FF_OPT_TYPE_BINARY, 0, 0, 0, D},
{"indexmem", "max memory used for timestamp index (per stream)", OFFSET(max_index_size), FF_OPT_TYPE_INT, 1<<20, 0, INT_MAX, D},
{"rtbufsize", "max memory used for buffering real-time frames", OFFSET(max_picture_buffer), FF_OPT_TYPE_INT, 3041280, 0, INT_MAX, D}, /* defaults to 1s of 15fps 352x288 YUYV422 video */
{"fdebug", "print specific debug info", OFFSET(debug), FF_OPT_TYPE_FLAGS, DEFAULT, 0, INT_MAX, E|D, "fdebug"},
{"ts", NULL, 0, FF_OPT_TYPE_CONST, FF_FDEBUG_TS, INT_MIN, INT_MAX, E|D, "fdebug"},
{NULL},
};

#undef E
#undef D
#undef DEFAULT

static const AVClass av_format_context_class = { "AVFormatContext", format_to_name, options };

static void avformat_get_context_defaults(AVFormatContext *s)
{
    memset(s, 0, sizeof(AVFormatContext));

    s->av_class = &av_format_context_class;

    av_opt_set_defaults(s);
}

AVFormatContext *av_alloc_format_context(void)
{
    AVFormatContext *ic;
    ic = av_malloc(sizeof(AVFormatContext));
    if (!ic) return ic;
    avformat_get_context_defaults(ic);
    ic->av_class = &av_format_context_class;
    return ic;
}

int av_open_input_stream(AVFormatContext **ic_ptr,
                         ByteIOContext *pb, const char *filename,
                         AVInputFormat *fmt, AVFormatParameters *ap)
{
    int err;
    AVFormatContext *ic;
    AVFormatParameters default_ap;

    if(!ap){
        ap=&default_ap;
        memset(ap, 0, sizeof(default_ap));
    }

    if(!ap->prealloced_context)
        ic = av_alloc_format_context();
    else
        ic = *ic_ptr;
    if (!ic) {
        err = AVERROR(ENOMEM);
        goto fail;
    }
    ic->iformat = fmt;
    ic->pb = pb;
    ic->duration = AV_NOPTS_VALUE;
    ic->start_time = AV_NOPTS_VALUE;
    av_strlcpy(ic->filename, filename, sizeof(ic->filename));

    /* allocate private data */
    if (fmt->priv_data_size > 0) {
        ic->priv_data = av_mallocz(fmt->priv_data_size);
        if (!ic->priv_data) {
            err = AVERROR(ENOMEM);
            goto fail;
        }
    } else {
        ic->priv_data = NULL;
    }

    if (ic->iformat->read_header) {
        err = ic->iformat->read_header(ic, ap);
        if (err < 0)
            goto fail;
    }

    if (pb && !ic->data_offset)
        ic->data_offset = url_ftell(ic->pb);

    *ic_ptr = ic;
    return 0;
 fail:
    if (ic) {
        int i;
        av_freep(&ic->priv_data);
        for(i=0;i<ic->nb_streams;i++) {
            AVStream *st = ic->streams[i];
            if (st) {
                av_free(st->priv_data);
                av_free(st->codec->extradata);
            }
            av_free(st);
        }
    }
    av_free(ic);
    *ic_ptr = NULL;
    return err;
}

/** size of probe buffer, for guessing file type from file contents */
#define PROBE_BUF_MIN 2048
#define PROBE_BUF_MAX (1<<20)

int av_open_input_file(AVFormatContext **ic_ptr, const char *filename,
                       AVInputFormat *fmt,
                       int buf_size,
                       AVFormatParameters *ap)
{
    int err, probe_size;
    AVProbeData probe_data, *pd = &probe_data;
    ByteIOContext *pb = NULL;

    pd->filename = "";
    if (filename)
        pd->filename = filename;
    pd->buf = NULL;
    pd->buf_size = 0;

    if (!fmt) {
        /* guess format if no file can be opened */
        fmt = av_probe_input_format(pd, 0);
    }

    /* Do not open file if the format does not need it. XXX: specific
       hack needed to handle RTSP/TCP */
    if (!fmt || !(fmt->flags & AVFMT_NOFILE)) {
        /* if no file needed do not try to open one */
        if ((err=url_fopen(&pb, filename, URL_RDONLY)) < 0) {
            goto fail;
        }
        if (buf_size > 0) {
            url_setbufsize(pb, buf_size);
        }

        for(probe_size= PROBE_BUF_MIN; probe_size<=PROBE_BUF_MAX && !fmt; probe_size<<=1){
            int score= probe_size < PROBE_BUF_MAX ? AVPROBE_SCORE_MAX/4 : 0;
            /* read probe data */
            pd->buf= av_realloc(pd->buf, probe_size + AVPROBE_PADDING_SIZE);
            pd->buf_size = get_buffer(pb, pd->buf, probe_size);
            memset(pd->buf+pd->buf_size, 0, AVPROBE_PADDING_SIZE);
            if (url_fseek(pb, 0, SEEK_SET) < 0) {
                url_fclose(pb);
                if (url_fopen(&pb, filename, URL_RDONLY) < 0) {
                    pb = NULL;
                    err = AVERROR(EIO);
                    goto fail;
                }
            }
            /* guess file format */
            fmt = av_probe_input_format2(pd, 1, &score);
        }
        av_freep(&pd->buf);
    }

    /* if still no format found, error */
    if (!fmt) {
        err = AVERROR_NOFMT;
        goto fail;
    }

    /* check filename in case an image number is expected */
    if (fmt->flags & AVFMT_NEEDNUMBER) {
        if (!av_filename_number_test(filename)) {
            err = AVERROR_NUMEXPECTED;
            goto fail;
        }
    }
    err = av_open_input_stream(ic_ptr, pb, filename, fmt, ap);
    if (err)
        goto fail;
    return 0;
 fail:
    av_freep(&pd->buf);
    if (pb)
        url_fclose(pb);
    *ic_ptr = NULL;
    return err;

}

/*******************************************************/

static AVPacket *add_to_pktbuf(AVPacketList **packet_buffer, AVPacket *pkt,
                               AVPacketList **plast_pktl){
    AVPacketList *pktl = av_mallocz(sizeof(AVPacketList));
    if (!pktl)
        return NULL;

    if (*packet_buffer)
        (*plast_pktl)->next = pktl;
    else
        *packet_buffer = pktl;

    /* add the packet in the buffered packet list */
    *plast_pktl = pktl;
    pktl->pkt= *pkt;
    return &pktl->pkt;
}

int av_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    int ret;
    AVStream *st;

    for(;;){
        AVPacketList *pktl = s->raw_packet_buffer;

        if (pktl) {
            *pkt = pktl->pkt;
            if(s->streams[pkt->stream_index]->codec->codec_id != CODEC_ID_PROBE){
                s->raw_packet_buffer = pktl->next;
                av_free(pktl);
                return 0;
            }
        }

        av_init_packet(pkt);
        ret= s->iformat->read_packet(s, pkt);
        if (ret < 0)
            return ret;
        st= s->streams[pkt->stream_index];

        switch(st->codec->codec_type){
        case CODEC_TYPE_VIDEO:
            if(s->video_codec_id)   st->codec->codec_id= s->video_codec_id;
            break;
        case CODEC_TYPE_AUDIO:
            if(s->audio_codec_id)   st->codec->codec_id= s->audio_codec_id;
            break;
        case CODEC_TYPE_SUBTITLE:
            if(s->subtitle_codec_id)st->codec->codec_id= s->subtitle_codec_id;
            break;
        }

        if(!pktl && st->codec->codec_id!=CODEC_ID_PROBE)
            return ret;

        add_to_pktbuf(&s->raw_packet_buffer, pkt, &s->raw_packet_buffer_end);

        if(st->codec->codec_id == CODEC_ID_PROBE){
            AVProbeData *pd = &st->probe_data;

            pd->buf = av_realloc(pd->buf, pd->buf_size+pkt->size+AVPROBE_PADDING_SIZE);
            memcpy(pd->buf+pd->buf_size, pkt->data, pkt->size);
            pd->buf_size += pkt->size;
            memset(pd->buf+pd->buf_size, 0, AVPROBE_PADDING_SIZE);

            if(av_log2(pd->buf_size) != av_log2(pd->buf_size - pkt->size)){
                set_codec_from_probe_data(st, pd, 1);
                if(st->codec->codec_id != CODEC_ID_PROBE){
                    pd->buf_size=0;
                    av_freep(&pd->buf);
                }
            }
        }
    }
}

/**********************************************************/

/**
 * Get the number of samples of an audio frame. Return -1 on error.
 */
static int get_audio_frame_size(AVCodecContext *enc, int size)
{
    int frame_size;

    if(enc->codec_id == CODEC_ID_VORBIS)
        return -1;

    if (enc->frame_size <= 1) {
        int bits_per_sample = av_get_bits_per_sample(enc->codec_id);

        if (bits_per_sample) {
            if (enc->channels == 0)
                return -1;
            frame_size = (size << 3) / (bits_per_sample * enc->channels);
        } else {
            /* used for example by ADPCM codecs */
            if (enc->bit_rate == 0)
                return -1;
            frame_size = (size * 8 * enc->sample_rate) / enc->bit_rate;
        }
    } else {
        frame_size = enc->frame_size;
    }
    return frame_size;
}


/**
 * Return the frame duration in seconds. Return 0 if not available.
 */
static void compute_frame_duration(int *pnum, int *pden, AVStream *st,
                                   AVCodecParserContext *pc, AVPacket *pkt)
{
    int frame_size;

    *pnum = 0;
    *pden = 0;
    switch(st->codec->codec_type) {
    case CODEC_TYPE_VIDEO:
        if(st->time_base.num*1000LL > st->time_base.den){
            *pnum = st->time_base.num;
            *pden = st->time_base.den;
        }else if(st->codec->time_base.num*1000LL > st->codec->time_base.den){
            *pnum = st->codec->time_base.num;
            *pden = st->codec->time_base.den;
            if (pc && pc->repeat_pict) {
                *pden *= 2;
                *pnum = (*pnum) * (2 + pc->repeat_pict);
            }
        }
        break;
    case CODEC_TYPE_AUDIO:
        frame_size = get_audio_frame_size(st->codec, pkt->size);
        if (frame_size < 0)
            break;
        *pnum = frame_size;
        *pden = st->codec->sample_rate;
        break;
    default:
        break;
    }
}

static int is_intra_only(AVCodecContext *enc){
    if(enc->codec_type == CODEC_TYPE_AUDIO){
        return 1;
    }else if(enc->codec_type == CODEC_TYPE_VIDEO){
        switch(enc->codec_id){
        case CODEC_ID_MJPEG:
        case CODEC_ID_MJPEGB:
        case CODEC_ID_LJPEG:
        case CODEC_ID_RAWVIDEO:
        case CODEC_ID_DVVIDEO:
        case CODEC_ID_HUFFYUV:
        case CODEC_ID_FFVHUFF:
        case CODEC_ID_ASV1:
        case CODEC_ID_ASV2:
        case CODEC_ID_VCR1:
        case CODEC_ID_DNXHD:
            return 1;
        default: break;
        }
    }
    return 0;
}

static void update_initial_timestamps(AVFormatContext *s, int stream_index,
                                      int64_t dts, int64_t pts)
{
    AVStream *st= s->streams[stream_index];
    AVPacketList *pktl= s->packet_buffer;

    if(st->first_dts != AV_NOPTS_VALUE || dts == AV_NOPTS_VALUE || st->cur_dts == AV_NOPTS_VALUE)
        return;

    st->first_dts= dts - st->cur_dts;
    st->cur_dts= dts;

    for(; pktl; pktl= pktl->next){
        if(pktl->pkt.stream_index != stream_index)
            continue;
        //FIXME think more about this check
        if(pktl->pkt.pts != AV_NOPTS_VALUE && pktl->pkt.pts == pktl->pkt.dts)
            pktl->pkt.pts += st->first_dts;

        if(pktl->pkt.dts != AV_NOPTS_VALUE)
            pktl->pkt.dts += st->first_dts;

        if(st->start_time == AV_NOPTS_VALUE && pktl->pkt.pts != AV_NOPTS_VALUE)
            st->start_time= pktl->pkt.pts;
    }
    if (st->start_time == AV_NOPTS_VALUE)
        st->start_time = pts;
}

static void update_initial_durations(AVFormatContext *s, AVStream *st, AVPacket *pkt)
{
    AVPacketList *pktl= s->packet_buffer;
    int64_t cur_dts= 0;

    if(st->first_dts != AV_NOPTS_VALUE){
        cur_dts= st->first_dts;
        for(; pktl; pktl= pktl->next){
            if(pktl->pkt.stream_index == pkt->stream_index){
                if(pktl->pkt.pts != pktl->pkt.dts || pktl->pkt.dts != AV_NOPTS_VALUE || pktl->pkt.duration)
                    break;
                cur_dts -= pkt->duration;
            }
        }
        pktl= s->packet_buffer;
        st->first_dts = cur_dts;
    }else if(st->cur_dts)
        return;

    for(; pktl; pktl= pktl->next){
        if(pktl->pkt.stream_index != pkt->stream_index)
            continue;
        if(pktl->pkt.pts == pktl->pkt.dts && pktl->pkt.dts == AV_NOPTS_VALUE
           && !pktl->pkt.duration){
            pktl->pkt.dts= cur_dts;
            if(!st->codec->has_b_frames)
                pktl->pkt.pts= cur_dts;
            cur_dts += pkt->duration;
            pktl->pkt.duration= pkt->duration;
        }else
            break;
    }
    if(st->first_dts == AV_NOPTS_VALUE)
        st->cur_dts= cur_dts;
}

static void compute_pkt_fields(AVFormatContext *s, AVStream *st,
                               AVCodecParserContext *pc, AVPacket *pkt)
{
    int num, den, presentation_delayed, delay, i;
    int64_t offset;

    /* do we have a video B-frame ? */
    delay= st->codec->has_b_frames;
    presentation_delayed = 0;
    /* XXX: need has_b_frame, but cannot get it if the codec is
        not initialized */
    if (delay &&
        pc && pc->pict_type != FF_B_TYPE)
        presentation_delayed = 1;

    if(pkt->pts != AV_NOPTS_VALUE && pkt->dts != AV_NOPTS_VALUE && pkt->dts > pkt->pts && st->pts_wrap_bits<63
       /*&& pkt->dts-(1LL<<st->pts_wrap_bits) < pkt->pts*/){
        pkt->dts -= 1LL<<st->pts_wrap_bits;
    }

    // some mpeg2 in mpeg-ps lack dts (issue171 / input_file.mpg)
    // we take the conservative approach and discard both
    // Note, if this is misbehaving for a H.264 file then possibly presentation_delayed is not set correctly.
    if(delay==1 && pkt->dts == pkt->pts && pkt->dts != AV_NOPTS_VALUE && presentation_delayed){
        av_log(s, AV_LOG_ERROR, "invalid dts/pts combination\n");
        pkt->dts= pkt->pts= AV_NOPTS_VALUE;
    }

    if (pkt->duration == 0) {
        compute_frame_duration(&num, &den, st, pc, pkt);
        if (den && num) {
            pkt->duration = av_rescale(1, num * (int64_t)st->time_base.den, den * (int64_t)st->time_base.num);

            if(pkt->duration != 0 && s->packet_buffer)
                update_initial_durations(s, st, pkt);
        }
    }

    /* correct timestamps with byte offset if demuxers only have timestamps
       on packet boundaries */
    if(pc && st->need_parsing == AVSTREAM_PARSE_TIMESTAMPS && pkt->size){
        /* this will estimate bitrate based on this frame's duration and size */
        offset = av_rescale(pc->offset, pkt->duration, pkt->size);
        if(pkt->pts != AV_NOPTS_VALUE)
            pkt->pts += offset;
        if(pkt->dts != AV_NOPTS_VALUE)
            pkt->dts += offset;
    }

    /* This may be redundant, but it should not hurt. */
    if(pkt->dts != AV_NOPTS_VALUE && pkt->pts != AV_NOPTS_VALUE && pkt->pts > pkt->dts)
        presentation_delayed = 1;

//    av_log(NULL, AV_LOG_DEBUG, "IN delayed:%d pts:%"PRId64", dts:%"PRId64" cur_dts:%"PRId64" st:%d pc:%p\n", presentation_delayed, pkt->pts, pkt->dts, st->cur_dts, pkt->stream_index, pc);
    /* interpolate PTS and DTS if they are not present */
    if(delay==0 || (delay==1 && pc)){
        if (presentation_delayed) {
            /* DTS = decompression timestamp */
            /* PTS = presentation timestamp */
            if (pkt->dts == AV_NOPTS_VALUE)
                pkt->dts = st->last_IP_pts;
            update_initial_timestamps(s, pkt->stream_index, pkt->dts, pkt->pts);
            if (pkt->dts == AV_NOPTS_VALUE)
                pkt->dts = st->cur_dts;

            /* this is tricky: the dts must be incremented by the duration
            of the frame we are displaying, i.e. the last I- or P-frame */
            if (st->last_IP_duration == 0)
                st->last_IP_duration = pkt->duration;
            if(pkt->dts != AV_NOPTS_VALUE)
                st->cur_dts = pkt->dts + st->last_IP_duration;
            st->last_IP_duration  = pkt->duration;
            st->last_IP_pts= pkt->pts;
            /* cannot compute PTS if not present (we can compute it only
            by knowing the future */
        } else if(pkt->pts != AV_NOPTS_VALUE || pkt->dts != AV_NOPTS_VALUE || pkt->duration){
            if(pkt->pts != AV_NOPTS_VALUE && pkt->duration){
                int64_t old_diff= FFABS(st->cur_dts - pkt->duration - pkt->pts);
                int64_t new_diff= FFABS(st->cur_dts - pkt->pts);
                if(old_diff < new_diff && old_diff < (pkt->duration>>3)){
                    pkt->pts += pkt->duration;
    //                av_log(NULL, AV_LOG_DEBUG, "id:%d old:%"PRId64" new:%"PRId64" dur:%d cur:%"PRId64" size:%d\n", pkt->stream_index, old_diff, new_diff, pkt->duration, st->cur_dts, pkt->size);
                }
            }

            /* presentation is not delayed : PTS and DTS are the same */
            if(pkt->pts == AV_NOPTS_VALUE)
                pkt->pts = pkt->dts;
            update_initial_timestamps(s, pkt->stream_index, pkt->pts, pkt->pts);
            if(pkt->pts == AV_NOPTS_VALUE)
                pkt->pts = st->cur_dts;
            pkt->dts = pkt->pts;
            if(pkt->pts != AV_NOPTS_VALUE)
                st->cur_dts = pkt->pts + pkt->duration;
        }
    }

    if(pkt->pts != AV_NOPTS_VALUE && delay <= MAX_REORDER_DELAY){
        st->pts_buffer[0]= pkt->pts;
        for(i=0; i<delay && st->pts_buffer[i] > st->pts_buffer[i+1]; i++)
            FFSWAP(int64_t, st->pts_buffer[i], st->pts_buffer[i+1]);
        if(pkt->dts == AV_NOPTS_VALUE)
            pkt->dts= st->pts_buffer[0];
        if(delay>1){
            update_initial_timestamps(s, pkt->stream_index, pkt->dts, pkt->pts); // this should happen on the first packet
        }
        if(pkt->dts > st->cur_dts)
            st->cur_dts = pkt->dts;
    }

//    av_log(NULL, AV_LOG_ERROR, "OUTdelayed:%d/%d pts:%"PRId64", dts:%"PRId64" cur_dts:%"PRId64"\n", presentation_delayed, delay, pkt->pts, pkt->dts, st->cur_dts);

    /* update flags */
    if(is_intra_only(st->codec))
        pkt->flags |= PKT_FLAG_KEY;
    else if (pc) {
        pkt->flags = 0;
        /* keyframe computation */
            if (pc->pict_type == FF_I_TYPE)
                pkt->flags |= PKT_FLAG_KEY;
    }
}

void av_destruct_packet_nofree(AVPacket *pkt)
{
    pkt->data = NULL; pkt->size = 0;
}

static int av_read_frame_internal(AVFormatContext *s, AVPacket *pkt)
{
    AVStream *st;
    int len, ret, i;

    av_init_packet(pkt);

    for(;;) {
        /* select current input stream component */
        st = s->cur_st;
        if (st) {
            if (!st->need_parsing || !st->parser) {
                /* no parsing needed: we just output the packet as is */
                /* raw data support */
                *pkt = s->cur_pkt;
                compute_pkt_fields(s, st, NULL, pkt);
                s->cur_st = NULL;
                break;
            } else if (s->cur_len > 0 && st->discard < AVDISCARD_ALL) {
                len = av_parser_parse(st->parser, st->codec, &pkt->data, &pkt->size,
                                      s->cur_ptr, s->cur_len,
                                      s->cur_pkt.pts, s->cur_pkt.dts);
                s->cur_pkt.pts = AV_NOPTS_VALUE;
                s->cur_pkt.dts = AV_NOPTS_VALUE;
                /* increment read pointer */
                s->cur_ptr += len;
                s->cur_len -= len;

                /* return packet if any */
                if (pkt->size) {
                got_packet:
                    pkt->pos = s->cur_pkt.pos;              // Isn't quite accurate but close.
                    pkt->duration = 0;
                    pkt->stream_index = st->index;
                    pkt->pts = st->parser->pts;
                    pkt->dts = st->parser->dts;
                    pkt->destruct = av_destruct_packet_nofree;
                    compute_pkt_fields(s, st, st->parser, pkt);

                    if((s->iformat->flags & AVFMT_GENERIC_INDEX) && pkt->flags & PKT_FLAG_KEY){
                        ff_reduce_index(s, st->index);
                        av_add_index_entry(st, st->parser->frame_offset, pkt->dts,
                                           0, 0, AVINDEX_KEYFRAME);
                    }

                    break;
                }
            } else {
                /* free packet */
                av_free_packet(&s->cur_pkt);