nsvdec.c

/*
 * NSV demuxer
 * Copyright (c) 2004 The FFmpeg Project
 *
 * first version by Francois Revol <revol@free.fr>
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "libavutil/attributes.h"
#include "libavutil/mathematics.h"
#include "libavutil/mem.h"
#include "avformat.h"
#include "demux.h"
#include "internal.h"
#include "libavutil/dict.h"
#include "libavutil/intreadwrite.h"

/* max bytes to crawl for trying to resync
 * stupid streaming servers don't start at chunk boundaries...
 */
#define NSV_MAX_RESYNC (500*1024)
#define NSV_MAX_RESYNC_TRIES 300

/*
 * References:
 * (1) http://www.multimedia.cx/nsv-format.txt
 * seems someone came to the same conclusions as me, and updated it:
 * (2) http://www.stud.ktu.lt/~vitslav/nsv/nsv-format.txt
 *     http://www.stud.ktu.lt/~vitslav/nsv/
 * official docs
 * (3) http://ultravox.aol.com/NSVFormat.rtf
 * Sample files:
 * (S1) http://www.nullsoft.com/nsv/samples/
 * http://www.nullsoft.com/nsv/samples/faster.nsv
 * http://streamripper.sourceforge.net/openbb/read.php?TID=492&page=4
 */

/*
 * notes on the header (Francois Revol):
 *
 * It is followed by strings, then a table, but nothing tells
 * where the table begins according to (1). After checking faster.nsv,
 * I believe NVSf[16-19] gives the size of the strings data
 * (that is the offset of the data table after the header).
 * After checking all samples from (S1) all confirms this.
 *
 * Then, about NSVf[12-15], faster.nsf has 179700. When viewing it in VLC,
 * I noticed there was about 1 NVSs chunk/s, so I ran
 * strings faster.nsv | grep NSVs | wc -l
 * which gave me 180. That leads me to think that NSVf[12-15] might be the
 * file length in milliseconds.
 * Let's try that:
 * for f in *.nsv; do HTIME="$(od -t x4 "$f" | head -1 | sed 's/.* //')"; echo "'$f' $((0x$HTIME))s = $((0x$HTIME/1000/60)):$((0x$HTIME/1000%60))"; done
 * except for nsvtrailer (which doesn't have an NSVf header), it reports correct time.
 *
 * nsvtrailer.nsv (S1) does not have any NSVf header, only NSVs chunks,
 * so the header seems to not be mandatory. (for streaming).
 *
 * index slice duration check (excepts nsvtrailer.nsv):
 * for f in [^n]*.nsv; do DUR="$(ffmpeg -i "$f" 2>/dev/null | grep 'NSVf duration' | cut -d ' ' -f 4)"; IC="$(ffmpeg -i "$f" 2>/dev/null | grep 'INDEX ENTRIES' | cut -d ' ' -f 2)"; echo "duration $DUR, slite time $(($DUR/$IC))"; done
 */

/*
 * TODO:
 * - handle timestamps !!!
 * - use index
 * - mime-type in probe()
 * - seek
 */

#if 0
struct NSVf_header {
    uint32_t chunk_tag; /* 'NSVf' */
    uint32_t chunk_size;
    uint32_t file_size; /* max 4GB ??? no one learns anything it seems :^) */
    uint32_t file_length; //unknown1;  /* what about MSB of file_size ? */
    uint32_t info_strings_size; /* size of the info strings */ //unknown2;
    uint32_t table_entries;
    uint32_t table_entries_used; /* the left ones should be -1 */
};

struct NSVs_header {
    uint32_t chunk_tag; /* 'NSVs' */
    uint32_t v4cc;      /* or 'NONE' */
    uint32_t a4cc;      /* or 'NONE' */
    uint16_t vwidth;    /* av_assert0(vwidth%16==0) */
    uint16_t vheight;   /* av_assert0(vheight%16==0) */
    uint8_t framerate;  /* value = (framerate&0x80)?frtable[frameratex0x7f]:framerate */
    uint16_t unknown;
};

struct nsv_avchunk_header {
    uint8_t vchunk_size_lsb;
    uint16_t vchunk_size_msb; /* value = (vchunk_size_msb << 4) | (vchunk_size_lsb >> 4) */
    uint16_t achunk_size;
};

struct nsv_pcm_header {
    uint8_t bits_per_sample;
    uint8_t channel_count;
    uint16_t sample_rate;
};
#endif

/* variation from avi.h */
/*typedef struct CodecTag {
    int id;
    unsigned int tag;
} CodecTag;*/

/* tags */

#define T_NSVF MKTAG('N', 'S', 'V', 'f') /* file header */
#define T_NSVS MKTAG('N', 'S', 'V', 's') /* chunk header */
#define T_TOC2 MKTAG('T', 'O', 'C', '2') /* extra index marker */
#define T_NONE MKTAG('N', 'O', 'N', 'E') /* null a/v 4CC */
#define T_SUBT MKTAG('S', 'U', 'B', 'T') /* subtitle aux data */
#define T_ASYN MKTAG('A', 'S', 'Y', 'N') /* async a/v aux marker */
#define T_KEYF MKTAG('K', 'E', 'Y', 'F') /* video keyframe aux marker (addition) */

#define TB_NSVF MKBETAG('N', 'S', 'V', 'f')
#define TB_NSVS MKBETAG('N', 'S', 'V', 's')

/* hardcoded stream indexes */
#define NSV_ST_VIDEO 0
#define NSV_ST_AUDIO 1
#define NSV_ST_SUBT 2

enum NSVStatus {
    NSV_UNSYNC,
    NSV_FOUND_NSVF,
    NSV_HAS_READ_NSVF,
    NSV_FOUND_NSVS,
    NSV_HAS_READ_NSVS,
    NSV_FOUND_BEEF,
    NSV_GOT_VIDEO,
    NSV_GOT_AUDIO,
};

typedef struct NSVStream {
    int frame_offset; /* current frame (video) or byte (audio) counter
                         (used to compute the pts) */
    int scale;
    int rate;
    int sample_size; /* audio only data */
    int start;

    int new_frame_offset; /* temporary storage (used during seek) */
    int cum_len; /* temporary storage (used during seek) */
} NSVStream;

typedef struct NSVContext {
    int  base_offset;
    int  NSVf_end;
    uint32_t *nsvs_file_offset;
    int index_entries;
    enum NSVStatus state;
    AVPacket ahead[2]; /* [v, a] if .data is !NULL there is something */
    /* cached */
    int64_t duration;
    uint32_t vtag, atag;
    uint16_t vwidth, vheight;
    int16_t avsync;
    AVRational framerate;
    uint32_t *nsvs_timestamps;
    int nsvf;
} NSVContext;

static const AVCodecTag nsv_codec_video_tags[] = {
    { AV_CODEC_ID_VP3, MKTAG('V', 'P', '3', ' ') },
    { AV_CODEC_ID_VP3, MKTAG('V', 'P', '3', '0') },
    { AV_CODEC_ID_VP3, MKTAG('V', 'P', '3', '1') },
    { AV_CODEC_ID_VP5, MKTAG('V', 'P', '5', ' ') },
    { AV_CODEC_ID_VP5, MKTAG('V', 'P', '5', '0') },
    { AV_CODEC_ID_VP6, MKTAG('V', 'P', '6', ' ') },
    { AV_CODEC_ID_VP6, MKTAG('V', 'P', '6', '0') },
    { AV_CODEC_ID_VP6, MKTAG('V', 'P', '6', '1') },
    { AV_CODEC_ID_VP6, MKTAG('V', 'P', '6', '2') },
    { AV_CODEC_ID_VP8, MKTAG('V', 'P', '8', '0') },
/*
    { AV_CODEC_ID_VP4, MKTAG('V', 'P', '4', ' ') },
    { AV_CODEC_ID_VP4, MKTAG('V', 'P', '4', '0') },
*/
    { AV_CODEC_ID_MPEG4, MKTAG('X', 'V', 'I', 'D') }, /* cf sample xvid decoder from nsv_codec_sdk.zip */
    { AV_CODEC_ID_H264,  MKTAG('H', '2', '6', '4') },
    { AV_CODEC_ID_RAWVIDEO, MKTAG('R', 'G', 'B', '3') },
    { AV_CODEC_ID_NONE, 0 },
};

static const AVCodecTag nsv_codec_audio_tags[] = {
    { AV_CODEC_ID_MP3,       MKTAG('M', 'P', '3', ' ') },
    { AV_CODEC_ID_AAC,       MKTAG('A', 'A', 'C', ' ') },
    { AV_CODEC_ID_AAC,       MKTAG('A', 'A', 'C', 'P') },
    { AV_CODEC_ID_AAC,       MKTAG('A', 'A', 'V', ' ') },
    { AV_CODEC_ID_AAC,       MKTAG('V', 'L', 'B', ' ') },
    { AV_CODEC_ID_SPEEX,     MKTAG('S', 'P', 'X', ' ') },
    { AV_CODEC_ID_PCM_U16LE, MKTAG('P', 'C', 'M', ' ') },
    { AV_CODEC_ID_NONE,      0 },
};

//static int nsv_load_index(AVFormatContext *s);
static int nsv_read_chunk(AVFormatContext *s, int fill_header);

/* try to find something we recognize, and set the state accordingly */
static int nsv_resync(AVFormatContext *s)
{
    NSVContext *nsv = s->priv_data;
    AVIOContext *pb = s->pb;
    uint32_t v = 0;
    int i;

    for (i = 0; i < NSV_MAX_RESYNC; i++) {
        if (avio_feof(pb)) {
            av_log(s, AV_LOG_TRACE, "NSV EOF\n");
            nsv->state = NSV_UNSYNC;
            return -1;
        }
        v <<= 8;
        v |= avio_r8(pb);
        if (i < 8) {
            av_log(s, AV_LOG_TRACE, "NSV resync: [%d] = %02"PRIx32"\n", i, v & 0x0FF);
        }

        if ((v & 0x0000ffff) == 0xefbe) { /* BEEF */
            av_log(s, AV_LOG_TRACE, "NSV resynced on BEEF after %d bytes\n", i+1);
            nsv->state = NSV_FOUND_BEEF;
            return 0;
        }
        /* we read as big-endian, thus the MK*BE* */
        if (v == TB_NSVF) { /* NSVf */
            av_log(s, AV_LOG_TRACE, "NSV resynced on NSVf after %d bytes\n", i+1);
            nsv->state = NSV_FOUND_NSVF;
            return 0;
        }
        if (v == MKBETAG('N', 'S', 'V', 's')) { /* NSVs */
            av_log(s, AV_LOG_TRACE, "NSV resynced on NSVs after %d bytes\n", i+1);
            nsv->state = NSV_FOUND_NSVS;
            return 0;
        }

    }
    av_log(s, AV_LOG_TRACE, "NSV sync lost\n");
    return -1;
}

static int nsv_parse_NSVf_header(AVFormatContext *s)
{
    NSVContext *nsv = s->priv_data;
    AVIOContext *pb = s->pb;
    unsigned int av_unused file_size;
    unsigned int size;
    int64_t duration;
    int strings_size;
    int table_entries;
    int table_entries_used;

    nsv->state = NSV_UNSYNC; /* in case we fail */

    if (nsv->nsvf) {
        av_log(s, AV_LOG_TRACE, "Multiple NSVf\n");
        return 0;
    }
    nsv->nsvf = 1;

    size = avio_rl32(pb);
    if (size < 28)
        return -1;
    nsv->NSVf_end = size;

    file_size = (uint32_t)avio_rl32(pb);
    av_log(s, AV_LOG_TRACE, "NSV NSVf chunk_size %u\n", size);
    av_log(s, AV_LOG_TRACE, "NSV NSVf file_size %u\n", file_size);

    nsv->duration = duration = avio_rl32(pb); /* in ms */
    av_log(s, AV_LOG_TRACE, "NSV NSVf duration %"PRId64" ms\n", duration);
    // XXX: store it in AVStreams

    strings_size = avio_rl32(pb);
    table_entries = avio_rl32(pb);
    table_entries_used = avio_rl32(pb);
    av_log(s, AV_LOG_TRACE, "NSV NSVf info-strings size: %d, table entries: %d, bis %d\n",
            strings_size, table_entries, table_entries_used);
    if (avio_feof(pb))
        return -1;

    av_log(s, AV_LOG_TRACE, "NSV got header; filepos %"PRId64"\n", avio_tell(pb));

    if (strings_size > 0) {
        char *strings; /* last byte will be '\0' to play safe with str*() */
        char *p, *endp;
        char *token, *value;
        char quote;

        p = strings = av_mallocz((size_t)strings_size + 1);
        if (!p)
            return AVERROR(ENOMEM);
        endp = strings + strings_size;
        avio_read(pb, strings, strings_size);
        while (p < endp) {
            while (*p == ' ')
                p++; /* strip out spaces */
            if (p >= endp-2)
                break;
            token = p;
            p = strchr(p, '=');
            if (!p || p >= endp-2)
                break;
            *p++ = '\0';
            quote = *p++;
            value = p;
            p = strchr(p, quote);
            if (!p || p >= endp)
                break;
            *p++ = '\0';
            av_log(s, AV_LOG_TRACE, "NSV NSVf INFO: %s='%s'\n", token, value);
            av_dict_set(&s->metadata, token, value, 0);
        }
        av_free(strings);
    }
    if (avio_feof(pb))
        return -1;

    av_log(s, AV_LOG_TRACE, "NSV got infos; filepos %"PRId64"\n", avio_tell(pb));

    if (table_entries_used > 0) {
        int i;
        nsv->index_entries = table_entries_used;
        if((unsigned)table_entries_used >= UINT_MAX / sizeof(uint32_t))
            return -1;
        nsv->nsvs_file_offset = av_malloc_array((unsigned)table_entries_used, sizeof(uint32_t));
        if (!nsv->nsvs_file_offset)
            return AVERROR(ENOMEM);

        for(i=0;i<table_entries_used;i++) {
            if (avio_feof(pb))
                return AVERROR_INVALIDDATA;
            nsv->nsvs_file_offset[i] = avio_rl32(pb) + size;
        }

        if(table_entries > table_entries_used &&
           avio_rl32(pb) == MKTAG('T','O','C','2')) {
            nsv->nsvs_timestamps = av_malloc_array((unsigned)table_entries_used, sizeof(uint32_t));
            if (!nsv->nsvs_timestamps)
                return AVERROR(ENOMEM);
            for(i=0;i<table_entries_used;i++) {
                nsv->nsvs_timestamps[i] = avio_rl32(pb);
            }
        }
    }

    av_log(s, AV_LOG_TRACE, "NSV got index; filepos %"PRId64"\n", avio_tell(pb));

    avio_seek(pb, nsv->base_offset + size, SEEK_SET); /* required for dumbdriving-271.nsv (2 extra bytes) */

    if (avio_feof(pb))
        return -1;
    nsv->state = NSV_HAS_READ_NSVF;
    return 0;
}

static int nsv_parse_NSVs_header(AVFormatContext *s)
{
    NSVContext *nsv = s->priv_data;
    AVIOContext *pb = s->pb;
    uint32_t vtag, atag;
    uint16_t vwidth, vheight;
    AVRational framerate;
    int i;
    AVStream *st;
    NSVStream *nst;

    vtag = avio_rl32(pb);
    atag = avio_rl32(pb);
    vwidth = avio_rl16(pb);
    vheight = avio_rl16(pb);
    i = avio_r8(pb);

    av_log(s, AV_LOG_TRACE, "NSV NSVs framerate code %2x\n", i);
    if(i&0x80) { /* odd way of giving native framerates from docs */
        int t=(i & 0x7F)>>2;
        if(t<16) framerate = (AVRational){1, t+1};
        else     framerate = (AVRational){t-15, 1};

        if(i&1){
            framerate.num *= 1000;
            framerate.den *= 1001;
        }

        if((i&3)==3)      framerate.num *= 24;
        else if((i&3)==2) framerate.num *= 25;
        else              framerate.num *= 30;
    }
    else
        framerate= (AVRational){i, 1};

    nsv->avsync = avio_rl16(pb);
    nsv->framerate = framerate;

    av_log(s, AV_LOG_TRACE, "NSV NSVs vsize %dx%d\n", vwidth, vheight);

    /* XXX change to ap != NULL ? */
    if (s->nb_streams == 0) { /* streams not yet published, let's do that */
        nsv->vtag = vtag;
        nsv->atag = atag;
        nsv->vwidth = vwidth;
        nsv->vheight = vwidth;
        if (vtag != T_NONE) {
            int i;
            st = avformat_new_stream(s, NULL);
            if (!st)
                goto fail;

            st->id = NSV_ST_VIDEO;
            nst = av_mallocz(sizeof(NSVStream));
            if (!nst)
                goto fail;
            st->priv_data = nst;
            st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
            st->codecpar->codec_tag = vtag;
            st->codecpar->codec_id = ff_codec_get_id(nsv_codec_video_tags, vtag);
            st->codecpar->width = vwidth;
            st->codecpar->height = vheight;
            st->codecpar->bits_per_coded_sample = 24; /* depth XXX */

            avpriv_set_pts_info(st, 64, framerate.den, framerate.num);
            st->start_time = 0;
            st->duration = av_rescale(nsv->duration, framerate.num, 1000*framerate.den);

            for(i=0;i<nsv->index_entries;i++) {
                if(nsv->nsvs_timestamps) {
                    av_add_index_entry(st, nsv->nsvs_file_offset[i], nsv->nsvs_timestamps[i],
                                       0, 0, AVINDEX_KEYFRAME);
                } else {
                    int64_t ts = av_rescale(i*nsv->duration/nsv->index_entries, framerate.num, 1000*framerate.den);
                    av_add_index_entry(st, nsv->nsvs_file_offset[i], ts, 0, 0, AVINDEX_KEYFRAME);
                }
            }
        }
        if (atag != T_NONE) {
            st = avformat_new_stream(s, NULL);
            if (!st)
                goto fail;

            st->id = NSV_ST_AUDIO;
            nst = av_mallocz(sizeof(NSVStream));
            if (!nst)
                goto fail;
            st->priv_data = nst;
            st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
            st->codecpar->codec_tag = atag;
            st->codecpar->codec_id = ff_codec_get_id(nsv_codec_audio_tags, atag);

            if (atag == MKTAG('A', 'A', 'V', ' ')) {
                static const uint8_t aav_pce[] = {
                    0x12, 0x00, 0x05, 0x08, 0x48, 0x00,
                    0x20, 0x00, 0xC6, 0x40, 0x04, 0x4C,
                    0x61, 0x76, 0x63, 0x56, 0xE5, 0x00,
                    0x00, 0x00,
                };
                int ret;

                if ((ret = ff_alloc_extradata(st->codecpar, sizeof(aav_pce))) < 0)
                    return ret;

                st->codecpar->sample_rate = 44100;
                memcpy(st->codecpar->extradata, aav_pce, sizeof(aav_pce));
            }

            ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL; /* for PCM we will read a chunk later and put correct info */

            /* set timebase to common denominator of ms and framerate */
            avpriv_set_pts_info(st, 64, 1, framerate.num*1000);
            st->start_time = 0;
            st->duration = (int64_t)nsv->duration * framerate.num;
        }
    } else {
        if (nsv->vtag != vtag || nsv->atag != atag || nsv->vwidth != vwidth || nsv->vheight != vwidth) {
            av_log(s, AV_LOG_TRACE, "NSV NSVs header values differ from the first one!!!\n");
            //return -1;
        }
    }

    nsv->state = NSV_HAS_READ_NSVS;
    return 0;
fail:
    /* XXX */
    nsv->state = NSV_UNSYNC;
    return -1;
}

static int nsv_read_header(AVFormatContext *s)
{
    NSVContext *nsv = s->priv_data;
    int i, err;

    nsv->state = NSV_UNSYNC;
    nsv->ahead[0].data = nsv->ahead[1].data = NULL;

    for (i = 0; i < NSV_MAX_RESYNC_TRIES; i++) {
        err = nsv_resync(s);
        if (err < 0)
            return err;
        if (nsv->state == NSV_FOUND_NSVF) {
            err = nsv_parse_NSVf_header(s);
            if (err < 0)
                return err;
        }
            /* we need the first NSVs also... */
        if (nsv->state == NSV_FOUND_NSVS) {
            err = nsv_parse_NSVs_header(s);
            if (err < 0)
                return err;
            break; /* we just want the first one */
        }
    }
    if (s->nb_streams < 1) /* no luck so far */
        return AVERROR_INVALIDDATA;

    /* now read the first chunk, so we can attempt to decode more info */
    err = nsv_read_chunk(s, 1);

    av_log(s, AV_LOG_TRACE, "parsed header\n");
    return err;
}

static int nsv_read_chunk(AVFormatContext *s, int fill_header)
{
    NSVContext *nsv = s->priv_data;
    AVIOContext *pb = s->pb;
    AVStream *st[2] = {NULL, NULL};
    NSVStream *nst;
    AVPacket *pkt;
    int i, err = 0;
    uint8_t auxcount; /* number of aux metadata, also 4 bits of vsize */
    uint32_t vsize;
    uint16_t asize;
    uint16_t auxsize;
    int ret;

    if (nsv->ahead[0].data || nsv->ahead[1].data)
        return 0; //-1; /* hey! eat what you've in your plate first! */

null_chunk_retry:
    if (avio_feof(pb))
        return -1;

    for (i = 0; i < NSV_MAX_RESYNC_TRIES && nsv->state < NSV_FOUND_NSVS && !err; i++)
        err = nsv_resync(s);
    if (err < 0)
        return err;
    if (nsv->state == NSV_FOUND_NSVS)
        err = nsv_parse_NSVs_header(s);
    if (err < 0)
        return err;
    if (nsv->state != NSV_HAS_READ_NSVS && nsv->state != NSV_FOUND_BEEF)
        return -1;

    auxcount = avio_r8(pb);
    vsize = avio_rl16(pb);
    asize = avio_rl16(pb);
    vsize = (vsize << 4) | (auxcount >> 4);
    auxcount &= 0x0f;
    av_log(s, AV_LOG_TRACE, "NSV CHUNK %d aux, %"PRIu32" bytes video, %d bytes audio\n", auxcount, vsize, asize);
    /* skip aux stuff */
    for (i = 0; i < auxcount; i++) {
        uint32_t av_unused auxtag;
        auxsize = avio_rl16(pb);
        auxtag = avio_rl32(pb);
        avio_skip(pb, auxsize);
        vsize -= auxsize + sizeof(uint16_t) + sizeof(uint32_t); /* that's becoming brain-dead */
    }

    if (avio_feof(pb))
        return -1;
    if (!vsize && !asize) {
        nsv->state = NSV_UNSYNC;
        goto null_chunk_retry;
    }

    /* map back streams to v,a */
    if (s->nb_streams > 0)
        st[s->streams[0]->id] = s->streams[0];
    if (s->nb_streams > 1)
        st[s->streams[1]->id] = s->streams[1];

    if (vsize && st[NSV_ST_VIDEO]) {
        nst = st[NSV_ST_VIDEO]->priv_data;
        pkt = &nsv->ahead[NSV_ST_VIDEO];
        if ((ret = av_get_packet(pb, pkt, vsize)) < 0)
            return ret;
        pkt->stream_index = st[NSV_ST_VIDEO]->index;//NSV_ST_VIDEO;
        pkt->dts = nst->frame_offset;
        pkt->flags |= nsv->state == NSV_HAS_READ_NSVS ? AV_PKT_FLAG_KEY : 0; /* keyframe only likely on a sync frame */
        for (i = 0; i < FFMIN(8, vsize); i++)
            av_log(s, AV_LOG_TRACE, "NSV video: [%d] = %02x\n", i, pkt->data[i]);
    }
    if(st[NSV_ST_VIDEO])
        ((NSVStream*)st[NSV_ST_VIDEO]->priv_data)->frame_offset++;

    if (asize && st[NSV_ST_AUDIO]) {
        nst = st[NSV_ST_AUDIO]->priv_data;
        pkt = &nsv->ahead[NSV_ST_AUDIO];
        /* read raw audio specific header on the first audio chunk... */
        /* on ALL audio chunks ?? seems so! */
        if (asize && st[NSV_ST_AUDIO]->codecpar->codec_tag == MKTAG('P', 'C', 'M', ' ')/* && fill_header*/) {
            uint8_t bps;
            uint8_t channels;
            uint16_t samplerate;
            bps = avio_r8(pb);
            channels = avio_r8(pb);
            samplerate = avio_rl16(pb);
            if (!channels || !samplerate)
                return AVERROR_INVALIDDATA;
            asize-=4;
            av_log(s, AV_LOG_TRACE, "NSV RAWAUDIO: bps %d, nchan %d, srate %d\n", bps, channels, samplerate);
            if (fill_header) {
                ffstream(st[NSV_ST_AUDIO])->need_parsing = AVSTREAM_PARSE_NONE; /* we know everything */
                if (bps != 16) {
                    av_log(s, AV_LOG_TRACE, "NSV AUDIO bit/sample != 16 (%d)!!!\n", bps);
                }
                bps /= channels; // ???
                if (bps == 8)
                    st[NSV_ST_AUDIO]->codecpar->codec_id = AV_CODEC_ID_PCM_U8;
                samplerate /= 4;/* UGH ??? XXX */
                channels = 1;
                st[NSV_ST_AUDIO]->codecpar->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
                st[NSV_ST_AUDIO]->codecpar->sample_rate = samplerate;
                av_log(s, AV_LOG_TRACE, "NSV RAWAUDIO: bps %d, nchan %d, srate %d\n", bps, channels, samplerate);
            }
        }
        if ((ret = av_get_packet(pb, pkt, asize)) < 0)
            return ret;
        pkt->stream_index = st[NSV_ST_AUDIO]->index;//NSV_ST_AUDIO;
        pkt->flags |= nsv->state == NSV_HAS_READ_NSVS ? AV_PKT_FLAG_KEY : 0; /* keyframe only likely on a sync frame */
        if( nsv->state == NSV_HAS_READ_NSVS && st[NSV_ST_VIDEO] ) {
            /* on a nsvs frame we have new information on a/v sync */
            pkt->dts = (((NSVStream*)st[NSV_ST_VIDEO]->priv_data)->frame_offset-1);
            pkt->dts *= (int64_t)1000        * nsv->framerate.den;
            pkt->dts += (int64_t)nsv->avsync * nsv->framerate.num;
            av_log(s, AV_LOG_TRACE, "NSV AUDIO: sync:%d, dts:%"PRId64, nsv->avsync, pkt->dts);
        }
        nst->frame_offset++;
    }

    nsv->state = NSV_UNSYNC;
    return 0;
}


static int nsv_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    NSVContext *nsv = s->priv_data;
    int i, err = 0;

    /* in case we don't already have something to eat ... */
    if (!nsv->ahead[0].data && !nsv->ahead[1].data)
        err = nsv_read_chunk(s, 0);
    if (err < 0)
        return err;

    /* now pick one of the plates */
    for (i = 0; i < 2; i++) {
        if (nsv->ahead[i].data) {
            av_packet_move_ref(pkt, &nsv->ahead[i]);
            return 0;
        }
    }

    /* this restaurant is not provisioned :^] */
    return -1;
}

static int nsv_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
{
    NSVContext *nsv = s->priv_data;
    AVStream *st = s->streams[stream_index];
    FFStream *const sti = ffstream(st);
    NSVStream *nst = st->priv_data;
    int index;

    index = av_index_search_timestamp(st, timestamp, flags);
    if(index < 0)
        return -1;

    if (avio_seek(s->pb, sti->index_entries[index].pos, SEEK_SET) < 0)
        return -1;

    nst->frame_offset = sti->index_entries[index].timestamp;
    nsv->state = NSV_UNSYNC;
    return 0;
}

static int nsv_read_close(AVFormatContext *s)
{
    NSVContext *nsv = s->priv_data;

    av_freep(&nsv->nsvs_file_offset);
    av_freep(&nsv->nsvs_timestamps);
    if (nsv->ahead[0].data)
        av_packet_unref(&nsv->ahead[0]);
    if (nsv->ahead[1].data)
        av_packet_unref(&nsv->ahead[1]);
    return 0;
}

static int nsv_probe(const AVProbeData *p)
{
    int i, score = 0;

    /* check file header */
    /* streamed files might not have any header */
    if (p->buf[0] == 'N' && p->buf[1] == 'S' &&
        p->buf[2] == 'V' && (p->buf[3] == 'f' || p->buf[3] == 's'))
        return AVPROBE_SCORE_MAX;
    /* XXX: do streamed files always start at chunk boundary ?? */
    /* or do we need to search NSVs in the byte stream ? */
    /* seems the servers don't bother starting clean chunks... */
    /* sometimes even the first header is at 9KB or something :^) */
    for (i = 1; i < p->buf_size - 3; i++) {
        if (AV_RL32(p->buf + i) == AV_RL32("NSVs")) {
            /* Get the chunk size and check if at the end we are getting 0xBEEF */
            int vsize = AV_RL24(p->buf+i+19) >> 4;
            int asize = AV_RL16(p->buf+i+22);
            int offset = i + 23 + asize + vsize + 1;
            if (offset <= p->buf_size - 2 && AV_RL16(p->buf + offset) == 0xBEEF)
                return 4*AVPROBE_SCORE_MAX/5;
            score = AVPROBE_SCORE_MAX/5;
        }
    }
    /* so we'll have more luck on extension... */
    if (av_match_ext(p->filename, "nsv"))
        return AVPROBE_SCORE_EXTENSION;
    /* FIXME: add mime-type check */
    return score;
}

const FFInputFormat ff_nsv_demuxer = {
    .p.name         = "nsv",
    .p.long_name    = NULL_IF_CONFIG_SMALL("Nullsoft Streaming Video"),
    .priv_data_size = sizeof(NSVContext),
    .flags_internal = FF_INFMT_FLAG_INIT_CLEANUP,
    .read_probe     = nsv_probe,
    .read_header    = nsv_read_header,
    .read_packet    = nsv_read_packet,
    .read_close     = nsv_read_close,
    .read_seek      = nsv_read_seek,
};