path: root/libavformat/nut.c

/*
 * "NUT" Container Format muxer and demuxer (DRAFT-200403??)
 * Copyright (c) 2003 Alex Beregszaszi
 * Copyright (c) 2004 Michael Niedermayer
 *
 * This library 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 of the License, or (at your option) any later version.
 *
 * This library 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 General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * NUT DRAFT can be found in MPlayer CVS at DOCS/tech/mpcf.txt
 *
 * AND http://people.fsn.hu/~alex/nut/ (TeX, pdf, ps, dvi, ..)
 *
 */

/*
 * TODO:
 * - seeking
 * - index writing
 * - index packet reading support
*/

//#define DEBUG 1

#include <limits.h>
#include "avformat.h"
#include "mpegaudio.h"
#include "avi.h"

#undef NDEBUG
#include <assert.h>

//from /dev/random

#define     MAIN_STARTCODE (0x7A561F5F04ADULL + (((uint64_t)('N'<<8) + 'M')<<48)) 
#define   STREAM_STARTCODE (0x11405BF2F9DBULL + (((uint64_t)('N'<<8) + 'S')<<48)) 
#define KEYFRAME_STARTCODE (0xE4ADEECA4569ULL + (((uint64_t)('N'<<8) + 'K')<<48)) 
#define    INDEX_STARTCODE (0xDD672F23E64EULL + (((uint64_t)('N'<<8) + 'X')<<48)) 
#define     INFO_STARTCODE (0xAB68B596BA78ULL + (((uint64_t)('N'<<8) + 'I')<<48)) 

#define MAX_TYPE1_DISTANCE (1024*16-1)
#define MAX_TYPE2_DISTANCE (1024*64-1)

#define MAX_SIZE_LRU 2
#define MAX_PTS_LRU 3

#define FLAG_FRAME_TYPE      1
#define FLAG_DATA_SIZE       2
#define FLAG_PTS            16
#define FLAG_FULL_PTS        4
#define FLAG_KEY_FRAME      32
#define FLAG_PRED_KEY_FRAME 64

typedef struct {
    uint8_t flags;
    uint8_t stream_id_plus1;
    uint8_t size_mul;
    uint8_t size_lsb;
} FrameCode;

typedef struct {
    int last_key_frame;
    int msb_timestamp_shift;
    int rate_num;
    int rate_den;
    int64_t last_pts;
    int64_t last_full_pts;
    int lru_pts_delta[MAX_PTS_LRU];
    int lru_size[MAX_SIZE_LRU];
    int initial_pts_predictor[MAX_PTS_LRU];
    int initial_size_predictor[MAX_SIZE_LRU];
    int64_t last_sync_pos;                    ///<pos of last 1/2 type frame
} StreamContext;

typedef struct {
    AVFormatContext *avf;
    int64_t packet_start;
    int64_t last_packet_start;
    int written_packet_size;
    int64_t packet_size_pos;
    int64_t last_frame_start[3];
    FrameCode frame_code[256];
    int stream_count;
    uint64_t next_startcode;     ///< stores the next startcode if it has alraedy been parsed but the stream isnt seekable
    StreamContext *stream;
} NUTContext;

static char *info_table[][2]={
	{NULL			,  NULL }, // end
	{NULL			,  NULL },
	{NULL			, "UTF8"},
	{NULL			, "v"},
	{NULL			, "s"},
	{"StreamId"		, "v"},
	{"SegmentId"		, "v"},
	{"StartTimestamp"	, "v"},
	{"EndTimestamp"		, "v"},
	{"Author"		, "UTF8"},
	{"Title"		, "UTF8"},
	{"Description"		, "UTF8"},
	{"Copyright"		, "UTF8"},
	{"Encoder"		, "UTF8"},
	{"Keyword"		, "UTF8"},
	{"Cover"		, "JPEG"},
	{"Cover"		, "PNG"},
};

static void update_lru(int *lru, int current, int count){
    int i;

    for(i=0; i<count-1; i++){
        if(lru[i] == current)
            break;
    }

    for(; i; i--){
        lru[i]= lru[i-1];
    }

    lru[0]= current;
}

static void update(NUTContext *nut, int stream_index, int64_t frame_start, int frame_type, int frame_code, int key_frame, int size, int64_t pts){
    StreamContext *stream= &nut->stream[stream_index];
    const int flags=nut->frame_code[frame_code].flags; 
    
    stream->last_key_frame= key_frame;
    nut->last_frame_start[ frame_type ]= frame_start;
    if(frame_type == 0)
        update_lru(stream->lru_pts_delta, pts - stream->last_pts, 3);
    update_lru(stream->lru_size, size, 2);
    stream->last_pts= pts;
    if((flags & FLAG_PTS) && (flags & FLAG_FULL_PTS))
        stream->last_full_pts= pts;
}

static void reset(AVFormatContext *s/*, int frame_type*/){
    NUTContext *nut = s->priv_data;
    int i;
    
    for(i=0; i<s->nb_streams; i++){
        StreamContext *stream= &nut->stream[i];
    
        stream->last_key_frame= 1;
        memcpy(stream->lru_pts_delta, stream->initial_pts_predictor, sizeof(int)*MAX_PTS_LRU);
        memcpy(stream->lru_size, stream->initial_size_predictor, sizeof(int)*MAX_SIZE_LRU);
    }
}

static void build_frame_code(AVFormatContext *s){
    NUTContext *nut = s->priv_data;
    int key_frame, frame_type, full_pts, index, pred, stream_id;
    int start=0;
    int end= 255;
    int keyframe_0_esc= s->nb_streams > 2;

    if(keyframe_0_esc){
        /* keyframe = 0 escapes, 3 codes */
        for(frame_type=0; frame_type<2; frame_type++){
            for(full_pts=frame_type; full_pts<2; full_pts++){
                FrameCode *ft= &nut->frame_code[start];
                ft->flags= FLAG_FRAME_TYPE*frame_type + FLAG_FULL_PTS*full_pts;
                ft->flags|= FLAG_DATA_SIZE | FLAG_PTS; 
                ft->stream_id_plus1= 0;
                ft->size_mul=1;
                start++;
            }
        }
    }

    for(stream_id= 0; stream_id<s->nb_streams; stream_id++){
        int start2= start + (end-start)*stream_id / s->nb_streams;
        int end2  = start + (end-start)*(stream_id+1) / s->nb_streams;
        AVCodecContext *codec = &s->streams[stream_id]->codec;
        int is_audio= codec->codec_type == CODEC_TYPE_AUDIO;
        int intra_only= /*codec->intra_only || */is_audio;
        int pred_count;

        for(key_frame=0; key_frame<2; key_frame++){
            if(intra_only && keyframe_0_esc && key_frame==0)
                continue;
            
            for(frame_type=0; frame_type<2; frame_type++){
                for(full_pts=frame_type; full_pts<2; full_pts++){
                    FrameCode *ft= &nut->frame_code[start2];
                    ft->flags= FLAG_FRAME_TYPE*frame_type + FLAG_FULL_PTS*full_pts + FLAG_KEY_FRAME*key_frame;
                    ft->flags|= FLAG_DATA_SIZE | FLAG_PTS;
                    ft->stream_id_plus1= stream_id + 1;
                    ft->size_mul=1;
                    start2++;
                }
            }
        }

        key_frame= intra_only;
#if 1
        if(is_audio){
            int frame_bytes= codec->frame_size*(int64_t)codec->bit_rate / (8*codec->sample_rate);
            for(pred=0; pred<MAX_SIZE_LRU; pred++){
                for(frame_type=0; frame_type<1; frame_type++){
                    FrameCode *ft= &nut->frame_code[start2];
                    ft->flags= FLAG_KEY_FRAME*key_frame + (FLAG_FULL_PTS+FLAG_PTS+FLAG_FRAME_TYPE)*frame_type;
                    ft->stream_id_plus1= stream_id + 1;
                    ft->size_mul=1;
                    ft->size_lsb=1 + pred;
                    start2++;
                }
                nut->stream[stream_id].initial_size_predictor[pred]= frame_bytes + pred;
            }
        }else{
            FrameCode *ft= &nut->frame_code[start2];
            ft->flags= FLAG_KEY_FRAME | FLAG_DATA_SIZE;
            ft->stream_id_plus1= stream_id + 1;
            ft->size_mul=1;
            start2++;
        }
#endif
        pred_count= 2 + codec->has_b_frames + (codec->codec_id == CODEC_ID_VORBIS);
        for(pred=0; pred<pred_count; pred++){
            int start3= start2 + (end2-start2)*pred / pred_count;
            int end3  = start2 + (end2-start2)*(pred+1) / pred_count;

            for(index=start3; index<end3; index++){
                FrameCode *ft= &nut->frame_code[index];
                ft->flags= FLAG_KEY_FRAME*key_frame + pred*4;
                ft->flags|= FLAG_DATA_SIZE;
                ft->stream_id_plus1= stream_id + 1;
//FIXME use single byte size and pred from last
                ft->size_mul= end3-start3;
                ft->size_lsb= index - start3;
            }
            nut->stream[stream_id].initial_pts_predictor[pred]= pred+1;
        }
    }
    memmove(&nut->frame_code['N'+1], &nut->frame_code['N'], sizeof(FrameCode)*(255-'N'));
    nut->frame_code['N'].flags= 1;
}

static uint64_t get_v(ByteIOContext *bc)
{
    uint64_t val = 0;

    for(;;)
    {
	int tmp = get_byte(bc);

	if (tmp&0x80)
	    val= (val<<7) + tmp - 0x80;
	else
	    return (val<<7) + tmp;
    }
    return -1;
}

static int get_str(ByteIOContext *bc, char *string, int maxlen){
    int len= get_v(bc);
    
    if(len && maxlen)
        get_buffer(bc, string, FFMIN(len, maxlen));
    while(len > maxlen){
        get_byte(bc);
        len--;
    }

    if(maxlen)
        string[FFMIN(len, maxlen-1)]= 0;
    
    if(maxlen == len)
        return -1;
    else
        return 0;
}

static uint64_t get_vb(ByteIOContext *bc){
    uint64_t val=0;
    int i= get_v(bc);
    
    if(i>8)
        return UINT64_MAX;
    
    while(i--)
        val = (val<<8) + get_byte(bc);
    
    return val;
}

static int get_packetheader(NUTContext *nut, ByteIOContext *bc, int prefix_length, int calculate_checksum)
{
    int64_t start, size, last_size;
    start= url_ftell(bc) - prefix_length;

    if(nut->written_packet_size >= 0 && start != nut->packet_start + nut->written_packet_size){
        av_log(nut->avf, AV_LOG_ERROR, "get_packetheader called at weird position\n");
        if(prefix_length<8)
            return -1;
    }
    
    init_checksum(bc, calculate_checksum ? update_adler32 : NULL, 0);

    size= get_v(bc);
    last_size= get_v(bc);
    if(nut->written_packet_size >= 0 && nut->written_packet_size != last_size){
        av_log(nut->avf, AV_LOG_ERROR, "packet size missmatch %d != %lld at %lld\n", nut->written_packet_size, last_size, start);
        if(prefix_length<8)
            return -1;
    }

    nut->last_packet_start = nut->packet_start;
    nut->packet_start = start;
    nut->written_packet_size= size;

    return size;
}

static int check_checksum(ByteIOContext *bc){
    unsigned long checksum= get_checksum(bc);
    return checksum != get_be32(bc);
}

/**
 * 
 */
static int get_length(uint64_t val){
    int i;

    for (i=7; val>>i; i+=7);

    return i;
}

static uint64_t find_any_startcode(ByteIOContext *bc, int64_t pos){
    uint64_t state=0;
    
    if(pos >= 0)
        url_fseek(bc, pos, SEEK_SET); //note, this may fail if the stream isnt seekable, but that shouldnt matter, as in this case we simply start where we are currently

    while(!url_feof(bc)){
        state= (state<<8) | get_byte(bc);
        if((state>>56) != 'N')
            continue;
        switch(state){
        case MAIN_STARTCODE:
        case STREAM_STARTCODE:
        case KEYFRAME_STARTCODE:
        case INFO_STARTCODE:
        case INDEX_STARTCODE:
            return state;
        }
    }

    return 0;
}

/**
 * find the given startcode.
 * @param code the startcode
 * @param pos the start position of the search, or -1 if the current position
 * @returns the position of the startcode or -1 if not found
 */
static int64_t find_startcode(ByteIOContext *bc, uint64_t code, int64_t pos){
    for(;;){
        uint64_t startcode= find_any_startcode(bc, pos);
        if(startcode == code)
            return url_ftell(bc) - 8;
        else if(startcode == 0)
            return -1;
        pos=-1;
    }
}

#ifdef CONFIG_ENCODERS
static void put_v(ByteIOContext *bc, uint64_t val)
{
    int i;

    val &= 0x7FFFFFFFFFFFFFFFULL; // FIXME can only encode upto 63 bits currently
    i= get_length(val);

    for (i-=7; i>0; i-=7){
	put_byte(bc, 0x80 | (val>>i));
    }

    put_byte(bc, val&0x7f);
}

/**
 * stores a string as vb.
 */
static void put_str(ByteIOContext *bc, const char *string){
    int len= strlen(string);
    
    put_v(bc, len);
    put_buffer(bc, string, len);
}

static void put_vb(ByteIOContext *bc, uint64_t val){
    int i;
    
    for (i=8; val>>i; i+=8);

    put_v(bc, i>>3);
    for(i-=8; i>=0; i-=8)
        put_byte(bc, (val>>i)&0xFF);
}

static int put_packetheader(NUTContext *nut, ByteIOContext *bc, int max_size, int calculate_checksum)
{
    put_flush_packet(bc);
    nut->last_packet_start= nut->packet_start;
    nut->packet_start+= nut->written_packet_size;
    nut->packet_size_pos = url_ftell(bc);
    nut->written_packet_size = max_size;
    
    if(calculate_checksum)
        init_checksum(bc, update_adler32, 0);

    /* packet header */
    put_v(bc, nut->written_packet_size); /* forward ptr */
    put_v(bc, nut->packet_start - nut->last_packet_start); /* backward ptr */

    return 0;
}

static int update_packetheader(NUTContext *nut, ByteIOContext *bc, int additional_size, int calculate_checksum){
    int64_t start= nut->packet_start;
    int64_t cur= url_ftell(bc);
    int size= cur - start + additional_size;
    
    if(calculate_checksum)
        size += 4;
    
    if(size != nut->written_packet_size){
        int i;

        assert( size <= nut->written_packet_size );
    
        url_fseek(bc, nut->packet_size_pos, SEEK_SET);
        for(i=get_length(size); i < get_length(nut->written_packet_size); i+=7)
            put_byte(bc, 0x80);
        put_v(bc, size);

        url_fseek(bc, cur, SEEK_SET);
        nut->written_packet_size= size; //FIXME may fail if multiple updates with differing sizes, as get_length may differ
        
        if(calculate_checksum)
            put_be32(bc, get_checksum(bc));
    }
    
    return 0;
}

static int nut_write_header(AVFormatContext *s)
{
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;
    AVCodecContext *codec;
    int i, j;

    nut->avf= s;
    
    nut->stream =	
	av_mallocz(sizeof(StreamContext)*s->nb_streams);
    
    av_set_pts_info(s, 60, 1, AV_TIME_BASE);
    
    /* main header */
    put_be64(bc, MAIN_STARTCODE);
    put_packetheader(nut, bc, 120+5*256, 1);
    put_v(bc, 1); /* version */
    put_v(bc, s->nb_streams);
    put_v(bc, 3);
    
    build_frame_code(s);
    assert(nut->frame_code['N'].flags == 1);
    for(i=0; i<256;){
        int tmp_flags = nut->frame_code[i].flags;
        int tmp_stream= nut->frame_code[i].stream_id_plus1;
        int tmp_mul   = nut->frame_code[i].size_mul;
        int tmp_size  = nut->frame_code[i].size_lsb;
        put_v(bc, tmp_flags);
        put_v(bc, tmp_stream);
        put_v(bc, tmp_mul);
        put_v(bc, tmp_size);

        for(j=0; i<256; j++,i++){
            if(nut->frame_code[i].flags           != tmp_flags ) break;
            if(nut->frame_code[i].stream_id_plus1 != tmp_stream) break;
            if(nut->frame_code[i].size_mul        != tmp_mul   ) break;
            if(nut->frame_code[i].size_lsb        != tmp_size  ) break;
            if(++tmp_size >= tmp_mul){
                tmp_size=0;
                tmp_stream++;
            }
        }
        put_v(bc, j);
    }

    update_packetheader(nut, bc, 0, 1);
    
    /* stream headers */
    for (i = 0; i < s->nb_streams; i++)
    {
	int nom, denom, gcd;

	codec = &s->streams[i]->codec;
	
	put_be64(bc, STREAM_STARTCODE);
	put_packetheader(nut, bc, 120 + codec->extradata_size, 1);
	put_v(bc, i /*s->streams[i]->index*/);
	put_v(bc, (codec->codec_type == CODEC_TYPE_AUDIO) ? 32 : 0);
	if (codec->codec_tag)
	    put_vb(bc, codec->codec_tag);
	else if (codec->codec_type == CODEC_TYPE_VIDEO)
	{
	    put_vb(bc, codec_get_bmp_tag(codec->codec_id));
	}
	else if (codec->codec_type == CODEC_TYPE_AUDIO)
	{
	    put_vb(bc, codec_get_wav_tag(codec->codec_id));
	}
        else
            put_vb(bc, 0);

	if (codec->codec_type == CODEC_TYPE_VIDEO)
	{
	    nom = codec->frame_rate;
	    denom = codec->frame_rate_base;
	}
	else
	{
	    nom = codec->sample_rate;
            if(codec->frame_size>0)
                denom= codec->frame_size;
            else
                denom= 1; //unlucky
	}
        gcd= ff_gcd(nom, denom);
        nom   /= gcd;
        denom /= gcd;
        nut->stream[i].rate_num= nom;
        nut->stream[i].rate_den= denom;

	put_v(bc, codec->bit_rate);
	put_vb(bc, 0); /* no language code */
	put_v(bc, nom);
	put_v(bc, denom);
        if(nom / denom < 1000)
	    nut->stream[i].msb_timestamp_shift = 7;
        else
	    nut->stream[i].msb_timestamp_shift = 14;
	put_v(bc, nut->stream[i].msb_timestamp_shift);
	for(j=0; j<3; j++)
		put_v(bc, nut->stream[i].initial_pts_predictor[j]);
	for(j=0; j<2; j++)
		put_v(bc, nut->stream[i].initial_size_predictor[j]);
	put_byte(bc, 0); /* flags: 0x1 - fixed_fps, 0x2 - index_present */
	
        if(codec->extradata_size){
            put_v(bc, 1);
            put_v(bc, codec->extradata_size);
            put_buffer(bc, codec->extradata, codec->extradata_size);            
        }
	put_v(bc, 0); /* end of codec specific headers */
	
	switch(codec->codec_type)
	{
	    case CODEC_TYPE_AUDIO:
		put_v(bc, (codec->sample_rate * denom) / nom);
		put_v(bc, codec->channels);
		break;
	    case CODEC_TYPE_VIDEO:
		put_v(bc, codec->width);
		put_v(bc, codec->height);
		put_v(bc, codec->sample_aspect_ratio.num);
		put_v(bc, codec->sample_aspect_ratio.den);
		put_v(bc, 0); /* csp type -- unknown */
		break;
            default:
                break;
	}
        update_packetheader(nut, bc, 0, 1);
    }

    /* info header */
    put_be64(bc, INFO_STARTCODE);
    put_packetheader(nut, bc, 30+strlen(s->author)+strlen(s->title)+
        strlen(s->comment)+strlen(s->copyright)+strlen(LIBAVFORMAT_IDENT), 1); 
    if (s->author[0])
    {
        put_v(bc, 9); /* type */
        put_str(bc, s->author);
    }
    if (s->title[0])
    {
        put_v(bc, 10); /* type */
        put_str(bc, s->title);
    }
    if (s->comment[0])
    {
        put_v(bc, 11); /* type */
        put_str(bc, s->comment);
    }
    if (s->copyright[0])
    {
        put_v(bc, 12); /* type */
        put_str(bc, s->copyright);
    }
    /* encoder */
    put_v(bc, 13); /* type */
    put_str(bc, LIBAVFORMAT_IDENT);
    
    put_v(bc, 0); /* eof info */
    update_packetheader(nut, bc, 0, 1);
        
    put_flush_packet(bc);
    
    return 0;
}

static int nut_write_packet(AVFormatContext *s, int stream_index, 
			    const uint8_t *buf, int size, int64_t pts)
{
    NUTContext *nut = s->priv_data;
    StreamContext *stream= &nut->stream[stream_index];
    ByteIOContext *bc = &s->pb;
    int key_frame = 0, full_pts=0;
    AVCodecContext *enc;
    int64_t lsb_pts, delta_pts;
    int frame_type, best_length, frame_code, flags, i, size_mul, size_lsb;
    const int64_t frame_start= url_ftell(bc);

    if (stream_index > s->nb_streams)
	return 1;
        
    pts= (av_rescale(pts, stream->rate_num, stream->rate_den) + AV_TIME_BASE/2) / AV_TIME_BASE;

    enc = &s->streams[stream_index]->codec;
    key_frame = enc->coded_frame->key_frame;
    delta_pts= pts - stream->last_pts;
    
    frame_type=0;
    if(frame_start + size + 20 - FFMAX(nut->last_frame_start[1], nut->last_frame_start[2]) > MAX_TYPE1_DISTANCE)
        frame_type=1;
    if(key_frame){
        if(frame_type==1 && frame_start + size - nut->last_frame_start[2] > MAX_TYPE2_DISTANCE)
            frame_type=2;
        if(!stream->last_key_frame)
            frame_type=2;
    }

    if(frame_type>0){
        update_packetheader(nut, bc, 0, 0);
        reset(s);
        full_pts=1;
    }
    //FIXME ensure that the timestamp can be represented by either delta or lsb or full_pts=1

    lsb_pts = pts & ((1 << stream->msb_timestamp_shift)-1);

    best_length=INT_MAX;
    frame_code= -1;
    for(i=0; i<256; i++){
        int stream_id_plus1= nut->frame_code[i].stream_id_plus1;
        int fc_key_frame= stream->last_key_frame;
        int length=0;
        size_mul= nut->frame_code[i].size_mul;
        size_lsb= nut->frame_code[i].size_lsb;
        flags= nut->frame_code[i].flags;

        if(stream_id_plus1 == 0) length+= get_length(stream_index);
        else if(stream_id_plus1 - 1 != stream_index)
            continue;
        if(flags & FLAG_PRED_KEY_FRAME){
            if(flags & FLAG_KEY_FRAME)
                fc_key_frame= !fc_key_frame;
        }else{
            fc_key_frame= !!(flags & FLAG_KEY_FRAME);
        }
        assert(key_frame==0 || key_frame==1);
        if(fc_key_frame != key_frame)
            continue;

        if((!!(flags & FLAG_FRAME_TYPE)) != (frame_type > 0))
            continue;
        
        if(size_mul <= size_lsb){
            int p= stream->lru_size[size_lsb - size_mul];
            if(p != size)
                continue;
        }else{
            if(size % size_mul != size_lsb)
                continue;
            if(flags & FLAG_DATA_SIZE)
                length += get_length(size / size_mul);
            else if(size/size_mul)
                continue;
        }

        if(full_pts != ((flags & FLAG_PTS) && (flags & FLAG_FULL_PTS)))
            continue;
            
        if(flags&FLAG_PTS){
            if(flags&FLAG_FULL_PTS){
                length += get_length(pts);
            }else{
                length += get_length(lsb_pts);
            }
        }else{
            int delta= stream->lru_pts_delta[(flags & 12)>>2];
            if(delta != pts - stream->last_pts)
                continue;
            assert(frame_type == 0);
        }

        if(length < best_length){
            best_length= length;
            frame_code=i;
        }
//    av_log(s, AV_LOG_DEBUG, "%d %d %d %d %d %d %d %d %d %d\n", key_frame, frame_type, full_pts, size, stream_index, flags, size_mul, size_lsb, stream_id_plus1, length);
    }

    assert(frame_code != -1);
    flags= nut->frame_code[frame_code].flags;
    size_mul= nut->frame_code[frame_code].size_mul;
    size_lsb= nut->frame_code[frame_code].size_lsb;
#if 0
    best_length /= 7;
    best_length ++; //frame_code
    if(frame_type>0){
        best_length += 4; //packet header
        if(frame_type>1)
            best_length += 8; // startcode
    }
    av_log(s, AV_LOG_DEBUG, "kf:%d ft:%d pt:%d fc:%2X len:%2d size:%d stream:%d flag:%d mul:%d lsb:%d s+1:%d pts_delta:%d\n", key_frame, frame_type, full_pts ? 2 : ((flags & FLAG_PTS) ? 1 : 0), frame_code, best_length, size, stream_index, flags, size_mul, size_lsb, nut->frame_code[frame_code].stream_id_plus1,(int)(pts - stream->last_pts));
#endif

    if (frame_type==2)
	put_be64(bc, KEYFRAME_STARTCODE);
    put_byte(bc, frame_code);

    if(frame_type>0)
        put_packetheader(nut, bc, FFMAX(size+20, MAX_TYPE1_DISTANCE), 0);
    if(nut->frame_code[frame_code].stream_id_plus1 == 0)
        put_v(bc, stream_index);
    if (flags & FLAG_PTS){
        if (flags & FLAG_FULL_PTS)
            put_v(bc, pts);
        else
            put_v(bc, lsb_pts);
    }
    if(flags & FLAG_DATA_SIZE)
        put_v(bc, size / size_mul);
    if(size > MAX_TYPE1_DISTANCE){
        assert(frame_type > 0);
        update_packetheader(nut, bc, size, 0);
    }
    
    put_buffer(bc, buf, size);

    update(nut, stream_index, frame_start, frame_type, frame_code, key_frame, size, pts);
    
    return 0;
}

static int nut_write_trailer(AVFormatContext *s)
{
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;

    update_packetheader(nut, bc, 0, 0);

#if 0
    int i;

    /* WRITE INDEX */

    for (i = 0; s->nb_streams; i++)
    {
	put_be64(bc, INDEX_STARTCODE);
	put_packetheader(nut, bc, 64, 1);
	put_v(bc, s->streams[i]->id);
	put_v(bc, ...);
        update_packetheader(nut, bc, 0, 1);
    }
#endif

    put_flush_packet(bc);
    
    av_freep(&nut->stream);

    return 0;
}
#endif //CONFIG_ENCODERS

static int nut_probe(AVProbeData *p)
{
    int i;
    uint64_t code;

    code = 0xff;
    for (i = 0; i < p->buf_size; i++) {
        int c = p->buf[i];
        code = (code << 8) | c;
        if (code == MAIN_STARTCODE)
            return AVPROBE_SCORE_MAX;
    }
    return 0;
}

static int decode_main_header(NUTContext *nut){
    AVFormatContext *s= nut->avf;
    ByteIOContext *bc = &s->pb;
    uint64_t tmp;
    int i, j;
    
    get_packetheader(nut, bc, 8, 1);

    tmp = get_v(bc);
    if (tmp != 1){
	av_log(s, AV_LOG_ERROR, "bad version (%Ld)\n", tmp);
        return -1;
    }
    
    nut->stream_count = get_v(bc);
    get_v(bc); //checksum threshold

    for(i=0; i<256;){
        int tmp_flags = get_v(bc);
        int tmp_stream= get_v(bc);
        int tmp_mul   = get_v(bc);
        int tmp_size  = get_v(bc);
        int count     = get_v(bc);

        if(count == 0 || i+count > 256){
            av_log(s, AV_LOG_ERROR, "illegal count %d at %d\n", count, i);
            return -1;
        }

        if((tmp_flags & FLAG_FRAME_TYPE) && tmp_flags != 1){
            if(tmp_flags & FLAG_PRED_KEY_FRAME){
                av_log(s, AV_LOG_ERROR, "keyframe prediction in non 0 frame type\n");
                return -1;
            }
            if(!(tmp_flags & FLAG_PTS) || !(tmp_flags & FLAG_FULL_PTS) ){
                av_log(s, AV_LOG_ERROR, "no full pts in non 0 frame type\n");
                return -1;
            }
        }

        for(j=0; j<count; j++,i++){
            if(tmp_stream > nut->stream_count + 1){
                av_log(s, AV_LOG_ERROR, "illegal stream number\n");
                return -1;
            }

            nut->frame_code[i].flags           = tmp_flags ;
            nut->frame_code[i].stream_id_plus1 = tmp_stream;
            nut->frame_code[i].size_mul        = tmp_mul   ;
            nut->frame_code[i].size_lsb        = tmp_size  ;
            if(++tmp_size >= tmp_mul){
                tmp_size=0;
                tmp_stream++;
            }
        }
    }
    if(nut->frame_code['N'].flags != 1){
        av_log(s, AV_LOG_ERROR, "illegal frame_code table\n");
        return -1;
    }

    if(check_checksum(bc)){
        av_log(s, AV_LOG_ERROR, "Main header checksum missmatch\n");
        return -1;
    }

    return 0;
}

static int decode_stream_header(NUTContext *nut){
    AVFormatContext *s= nut->avf;
    ByteIOContext *bc = &s->pb;
    int class, nom, denom, stream_id, i;
    uint64_t tmp;
    AVStream *st;
    
    get_packetheader(nut, bc, 8, 1);
    stream_id= get_v(bc);
    if(stream_id >= nut->stream_count || s->streams[stream_id])
        return -1;
    
    st = av_new_stream(s, stream_id);
    if (!st)
        return AVERROR_NOMEM;
    class = get_v(bc);
    tmp = get_vb(bc);
    switch(class)
    {
        case 0:
            st->codec.codec_type = CODEC_TYPE_VIDEO;
            st->codec.codec_id = codec_get_bmp_id(tmp);
            if (st->codec.codec_id == CODEC_ID_NONE)
                av_log(s, AV_LOG_ERROR, "Unknown codec?!\n");
            break;
        case 32:
            st->codec.codec_type = CODEC_TYPE_AUDIO;
            st->codec.codec_id = codec_get_wav_id(tmp);
            if (st->codec.codec_id == CODEC_ID_NONE)
                av_log(s, AV_LOG_ERROR, "Unknown codec?!\n");
            break;
        default:
            av_log(s, AV_LOG_ERROR, "Unknown stream class (%d)\n", class);
            return -1;
    }
    s->bit_rate += get_v(bc);
    get_vb(bc); /* language code */
    nom = get_v(bc);
    denom = get_v(bc);
    nut->stream[stream_id].msb_timestamp_shift = get_v(bc);
    for(i=0; i<3; i++)
            nut->stream[stream_id].initial_pts_predictor[i]= get_v(bc);
    for(i=0; i<2; i++)
            nut->stream[stream_id].initial_size_predictor[i]= get_v(bc);
    get_byte(bc); /* flags */

    /* codec specific data headers */
    while(get_v(bc) != 0){
        st->codec.extradata_size= get_v(bc);
        st->codec.extradata= av_mallocz(st->codec.extradata_size);
        get_buffer(bc, st->codec.extradata, st->codec.extradata_size);            
//	    url_fskip(bc, get_v(bc));
    }
    
    if (class == 0) /* VIDEO */
    {
        st->codec.width = get_v(bc);
        st->codec.height = get_v(bc);
        st->codec.sample_aspect_ratio.num= get_v(bc);
        st->codec.sample_aspect_ratio.den= get_v(bc);
        get_v(bc); /* csp type */

        st->codec.frame_rate = nom;
        st->codec.frame_rate_base = denom;
    }
    if (class == 32) /* AUDIO */
    {
        st->codec.sample_rate = (get_v(bc) * nom) / denom;
        st->codec.channels = get_v(bc);
    }
    if(check_checksum(bc)){
        av_log(s, AV_LOG_ERROR, "Stream header %d checksum missmatch\n", stream_id);
        return -1;
    }
    nut->stream[stream_id].rate_num= nom;
    nut->stream[stream_id].rate_den= denom;
    return 0;
}

static int decode_info_header(NUTContext *nut){
    AVFormatContext *s= nut->avf;
    ByteIOContext *bc = &s->pb;
    
    get_packetheader(nut, bc, 8, 1);

    for(;;){
        int id= get_v(bc);
        char *name, *type, custom_name[256], custom_type[256];

        if(!id)
            break;
        else if(id >= sizeof(info_table)/sizeof(info_table[0])){
            av_log(s, AV_LOG_ERROR, "info id is too large %d %d\n", id, sizeof(info_table)/sizeof(info_table[0]));
            return -1;
        }

        type= info_table[id][1];
        name= info_table[id][0];
//av_log(s, AV_LOG_DEBUG, "%d %s %s\n", id, type, name);

        if(!type){
            get_str(bc, custom_type, sizeof(custom_type));
            type= custom_type;
        }
        if(!name){
            get_str(bc, custom_name, sizeof(custom_name));
            name= custom_name;
        }
        
        if(!strcmp(type, "v")){
            int value= get_v(bc);
        }else{
            if(!strcmp(name, "Author"))
                get_str(bc, s->author, sizeof(s->author));
            else if(!strcmp(name, "Title"))
                get_str(bc, s->title, sizeof(s->title));
            else if(!strcmp(name, "Copyright"))
                get_str(bc, s->copyright, sizeof(s->copyright));
            else if(!strcmp(name, "Description"))
                get_str(bc, s->comment, sizeof(s->comment));
            else
                get_str(bc, NULL, 0);
        }
    }
    if(check_checksum(bc)){
        av_log(s, AV_LOG_ERROR, "Info header checksum missmatch\n");
        return -1;
    }
    return 0;
}

static int nut_read_header(AVFormatContext *s, AVFormatParameters *ap)
{
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;
    int64_t pos;
    int inited_stream_count;

    nut->avf= s;
    
    av_set_pts_info(s, 60, 1, AV_TIME_BASE);

    /* main header */
    pos=0;
    for(;;){
        pos= find_startcode(bc, MAIN_STARTCODE, pos)+1;
        if (pos<0){
            av_log(s, AV_LOG_ERROR, "no main startcode found\n");
            return -1;
        }
        if(decode_main_header(nut) >= 0)
            break;
    }
    
    
    s->bit_rate = 0;

    nut->stream = av_malloc(sizeof(StreamContext)*nut->stream_count);

    /* stream headers */
    pos=0;
    for(inited_stream_count=0; inited_stream_count < nut->stream_count;){
        pos= find_startcode(bc, STREAM_STARTCODE, pos)+1;
        if (pos<0){
            av_log(s, AV_LOG_ERROR, "not all stream headers found\n");
            return -1;
        }
        if(decode_stream_header(nut) >= 0)
            inited_stream_count++;
    }

    /* info headers */
    pos=0;
    for(;;){
        uint64_t startcode= find_any_startcode(bc, pos);
        pos= url_ftell(bc);

        if(startcode==0){
            av_log(s, AV_LOG_ERROR, "EOF before video frames\n");
            return -1;
        }else if(startcode == KEYFRAME_STARTCODE){
            nut->next_startcode= startcode;
            break;
        }else if(startcode != INFO_STARTCODE){
            continue;
        }

        decode_info_header(nut);
    }

    return 0;
}

static int decode_frame(NUTContext *nut, AVPacket *pkt, int frame_code, int frame_type){
    AVFormatContext *s= nut->avf;
    StreamContext *stream;
    ByteIOContext *bc = &s->pb;
    int size, flags, size_mul, size_lsb, stream_id;
    int key_frame = 0;
    int64_t pts = 0;
    const int prefix_len= frame_type == 2 ? 8+1 : 1;
    const int64_t frame_start= url_ftell(bc) - prefix_len;

    flags= nut->frame_code[frame_code].flags;
    size_mul= nut->frame_code[frame_code].size_mul;
    size_lsb= nut->frame_code[frame_code].size_lsb;
    stream_id= nut->frame_code[frame_code].stream_id_plus1 - 1;

    if(flags & FLAG_FRAME_TYPE){
        reset(s);
        if(get_packetheader(nut, bc, prefix_len, 0) < 0)
            return -1;
        if(frame_type!=2)
            frame_type= 1;
    }

    if(stream_id==-1)
        stream_id= get_v(bc);
    if(stream_id >= s->nb_streams){
        av_log(s, AV_LOG_ERROR, "illegal stream_id\n");
        return -1;
    }
    stream= &nut->stream[stream_id];

//    av_log(s, AV_LOG_DEBUG, "ft:%d ppts:%d %d %d\n", frame_type, stream->lru_pts_delta[0], stream->lru_pts_delta[1], stream->lru_pts_delta[2]);
    
    if(flags & FLAG_PRED_KEY_FRAME){
        if(flags & FLAG_KEY_FRAME)
            key_frame= !stream->last_key_frame;
        else
            key_frame= stream->last_key_frame;
    }else{
        key_frame= !!(flags & FLAG_KEY_FRAME);
    }

    if(flags & FLAG_PTS){
        if(flags & FLAG_FULL_PTS){
            pts= get_v(bc);
            if(frame_type && key_frame){
                av_add_index_entry(
                    s->streams[stream_id], 
                    frame_start, 
                    pts, 
                    frame_start - nut->stream[stream_id].last_sync_pos,
                    AVINDEX_KEYFRAME);
                nut->stream[stream_id].last_sync_pos= frame_start;
                assert(nut->packet_start == frame_start);
            }
        }else{
            int64_t mask = (1<<stream->msb_timestamp_shift)-1;
            int64_t delta= stream->last_pts - mask/2;
            pts= ((get_v(bc) - delta)&mask) + delta;
        }
    }else{
        pts= stream->last_pts + stream->lru_pts_delta[(flags&12)>>2];
    }
  
    if(size_mul <= size_lsb){
        size= stream->lru_size[size_lsb - size_mul];
    }else{
        if(flags & FLAG_DATA_SIZE)
            size= size_mul*get_v(bc) + size_lsb;
        else
            size= size_lsb;
    }
      
//av_log(s, AV_LOG_DEBUG, "fs:%lld fc:%d ft:%d kf:%d pts:%lld size:%d\n", frame_start, frame_code, frame_type, key_frame, pts, size);

    if(url_ftell(bc) - nut->packet_start + size > nut->written_packet_size){
        av_log(s, AV_LOG_ERROR, "frame size too large\n");
        return -1;
    }
    
    av_new_packet(pkt, size);
    get_buffer(bc, pkt->data, size);
    pkt->stream_index = stream_id;
    if (key_frame)
	pkt->flags |= PKT_FLAG_KEY;
    pkt->pts = pts * AV_TIME_BASE * stream->rate_den / stream->rate_num;

    update(nut, stream_id, frame_start, frame_type, frame_code, key_frame, size, pts);
    
    return 0;
}

static int nut_read_packet(AVFormatContext *s, AVPacket *pkt)
{
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;
    int size, i, frame_code=0;
    int64_t pos;

    for(;;){
        int frame_type= 0;
        uint64_t tmp= nut->next_startcode;
        nut->next_startcode=0;

        if (url_feof(bc))
            return -1;

        if(!tmp){
            frame_code = get_byte(bc);
            if(frame_code == 'N'){
                tmp= frame_code;
                for(i=1; i<8; i++)
                    tmp = (tmp<<8) + get_byte(bc);
            }
        }
        switch(tmp){
        case MAIN_STARTCODE:
        case STREAM_STARTCODE:
        case INDEX_STARTCODE:
            get_packetheader(nut, bc, 8, 0);
            url_fseek(bc, nut->written_packet_size + nut->packet_start, SEEK_SET);
            break;
        case INFO_STARTCODE:
            if(decode_info_header(nut)<0)
                goto resync;
            break;
        case KEYFRAME_STARTCODE:
            frame_type = 2;
            frame_code = get_byte(bc);
        case 0:
            if(decode_frame(nut, pkt, frame_code, frame_type)>=0)
                return 0;
        default:
resync:
av_log(s, AV_LOG_DEBUG, "syncing from %lld\n", nut->packet_start+1);
            tmp= find_any_startcode(bc, nut->packet_start+1);
            if(tmp==0)
                return -1;
av_log(s, AV_LOG_DEBUG, "sync\n");
            if(url_is_streamed(bc)){
                nut->next_startcode= tmp;
                break;
            }

            pos= url_ftell(bc) - 8;
av_log(s, AV_LOG_DEBUG, "at %lld code=%llX\n", pos, tmp);
            if(tmp==KEYFRAME_STARTCODE){
                get_byte(bc);
            }
            get_v(bc);
            size= get_v(bc);
            
            while(size > 2 && size < 100000 && nut->packet_start < pos - size){
                url_fseek(bc, pos - size, SEEK_SET);
                frame_code= get_byte(bc);
                if(!(nut->frame_code[ frame_code ].flags & FLAG_FRAME_TYPE))
                    break;
                if(get_v(bc) != size)
                    break;
                pos -= size;
                size= get_v(bc);
av_log(s, AV_LOG_DEBUG, "steping back to %lld next %d\n", pos, size);
            }
            url_fseek(bc, pos, SEEK_SET);
            
            nut->written_packet_size= -1;
        }
    }
}

static int64_t read_timestamp(AVFormatContext *s, int stream_index, int64_t *pos_arg, int64_t pos_limit){
    NUTContext *nut = s->priv_data;
    ByteIOContext *bc = &s->pb;
    int64_t pos, pts;
    uint64_t code;
    int frame_code,step, flags, stream_id, i;
av_log(s, AV_LOG_DEBUG, "read_timestamp(X,%d,%lld,%lld)\n", stream_index, *pos_arg, pos_limit);

    if(*pos_arg < 0)
        return AV_NOPTS_VALUE;

    // find a previous startcode, FIXME use forward search and follow backward pointers if undamaged stream
    pos= *pos_arg;
    step= FFMIN(16*1024, pos);
    do{
        pos-= step;
        code= find_any_startcode(bc, pos);

        if(code && url_ftell(bc) - 8 < *pos_arg)
            break;
        step= FFMIN(2*step, pos);
    }while(step);

    if(!code) //nothing found, not even after pos_arg
        return AV_NOPTS_VALUE;

    url_fseek(bc, -8, SEEK_CUR);
    for(i=0; i<s->nb_streams; i++)
        nut->stream[i].last_sync_pos= url_ftell(bc);
        
    for(;;){
        int64_t pos= url_ftell(bc);
        uint64_t tmp=0;
        int prefix_len=1;
        
        if(pos > pos_limit)
            return AV_NOPTS_VALUE;

        frame_code = get_byte(bc);
        if(frame_code == 'N'){
            tmp= frame_code;
            for(i=1; i<8; i++)
                tmp = (tmp<<8) + get_byte(bc);
        }
//av_log(s, AV_LOG_DEBUG, "before switch %llX at=%lld\n", tmp, pos);

        switch(tmp){
        case MAIN_STARTCODE:
        case STREAM_STARTCODE:
        case INDEX_STARTCODE:
        case INFO_STARTCODE:
            nut->written_packet_size= -1;
            get_packetheader(nut, bc, 8, 0);
            url_fseek(bc, nut->written_packet_size + nut->packet_start, SEEK_SET);
            break;
        case KEYFRAME_STARTCODE:
            nut->written_packet_size= -1;
            prefix_len+=8;
            frame_code = get_byte(bc);
        case 0:
            flags= nut->frame_code[frame_code].flags;
            stream_id= nut->frame_code[frame_code].stream_id_plus1 - 1;

            if(get_packetheader(nut, bc, prefix_len, 0) < 0)
                goto resync;

            if(!(flags & FLAG_FRAME_TYPE) || !(flags & FLAG_PTS) || !(flags & FLAG_FULL_PTS))
                goto resync;

            if(stream_id==-1)
                stream_id= get_v(bc);
            if(stream_id >= s->nb_streams)
                goto resync;
                
            pts= get_v(bc);
    
            if(flags & FLAG_KEY_FRAME){
                av_add_index_entry(
                    s->streams[stream_id], 
                    pos, 
                    pts, 
                    pos - nut->stream[stream_id].last_sync_pos,
                    AVINDEX_KEYFRAME);
                nut->stream[stream_id].last_sync_pos= pos;
            }
            if(stream_id != stream_index || !(flags & FLAG_KEY_FRAME) || nut->packet_start < *pos_arg){
                url_fseek(bc, nut->written_packet_size + nut->packet_start, SEEK_SET);
                break;
            }
 
            *pos_arg= nut->packet_start;
            assert(nut->packet_start == pos);
            return pts;
        default:
resync:
av_log(s, AV_LOG_DEBUG, "syncing from %lld\n", nut->packet_start+1);
            if(!find_any_startcode(bc, nut->packet_start+1))
                return AV_NOPTS_VALUE;

            url_fseek(bc, -8, SEEK_CUR);
        }
    }
    return AV_NOPTS_VALUE;
}

#define DEBUG_SEEK
static int nut_read_seek(AVFormatContext *s, int stream_index, int64_t target_ts){
    NUTContext *nut = s->priv_data;
    StreamContext *stream;
    int64_t pos_min, pos_max, pos, pos_limit;
    int64_t ts_min, ts_max, ts;
    int64_t start_pos;
    int index, no_change,i;
    AVStream *st;

    if (stream_index < 0) {
        stream_index = av_find_default_stream_index(s);
        if (stream_index < 0)
            return -1;
    }
    stream= &nut->stream[stream_index];
    target_ts= (av_rescale(target_ts, stream->rate_num, stream->rate_den) + AV_TIME_BASE/2) / AV_TIME_BASE;

#ifdef DEBUG_SEEK
    av_log(s, AV_LOG_DEBUG, "read_seek: %d %lld\n", stream_index, target_ts);
#endif

    ts_max=
    ts_min= AV_NOPTS_VALUE;
    pos_limit= -1; //gcc falsely says it may be uninitalized

    st= s->streams[stream_index];
    if(st->index_entries){
        AVIndexEntry *e;

        index= av_index_search_timestamp(st, target_ts);
        e= &st->index_entries[index];

        if(e->timestamp <= target_ts || e->pos == e->min_distance){
            pos_min= e->pos;
            ts_min= e->timestamp;
#ifdef DEBUG_SEEK
        av_log(s, AV_LOG_DEBUG, "unsing cached pos_min=0x%llx dts_min=%lld\n", 
               pos_min,ts_min);
#endif
        }else{
            assert(index==0);
        }
        index++;
        if(index < st->nb_index_entries){
            e= &st->index_entries[index];
            assert(e->timestamp >= target_ts);
            pos_max= e->pos;
            ts_max= e->timestamp;
            pos_limit= pos_max - e->min_distance;
#ifdef DEBUG_SEEK
        av_log(s, AV_LOG_DEBUG, "unsing cached pos_max=0x%llx pos_limit=0x%llx dts_max=%lld\n", 
               pos_max,pos_limit, ts_max);
#endif
        }
    }

    if(ts_min == AV_NOPTS_VALUE){
        pos_min = 0;
        ts_min = read_timestamp(s, stream_index, &pos_min, INT64_MAX);
        if (ts_min == AV_NOPTS_VALUE)
            return -1;
    }

    if(ts_max == AV_NOPTS_VALUE){
        int step= 1024;
        pos_max = url_filesize(url_fileno(&s->pb)) - 1;
        do{
            pos_max -= step;
            ts_max = read_timestamp(s, stream_index, &pos_max, pos_max + step);
            step += step;
        }while(ts_max == AV_NOPTS_VALUE && pos_max >= step);
        if (ts_max == AV_NOPTS_VALUE)
            return -1;
        
        for(;;){
            int64_t tmp_pos= pos_max + 1;
            int64_t tmp_ts= read_timestamp(s, stream_index, &tmp_pos, INT64_MAX);
            if(tmp_ts == AV_NOPTS_VALUE)
                break;
            ts_max= tmp_ts;
            pos_max= tmp_pos;
        }
        pos_limit= pos_max;
    }

    no_change=0;
    while (pos_min < pos_limit) {
#ifdef DEBUG_SEEK
        av_log(s, AV_LOG_DEBUG, "pos_min=0x%llx pos_max=0x%llx dts_min=%lld dts_max=%lld\n", 
               pos_min, pos_max,
               ts_min, ts_max);
#endif
        assert(pos_limit <= pos_max);

        if(no_change==0){
            int64_t approximate_keyframe_distance= pos_max - pos_limit;
            // interpolate position (better than dichotomy)
            pos = (int64_t)((double)(pos_max - pos_min) *
                            (double)(target_ts - ts_min) /
                            (double)(ts_max - ts_min)) + pos_min - approximate_keyframe_distance;
        }else if(no_change==1){
            // bisection, if interpolation failed to change min or max pos last time
            pos = (pos_min + pos_limit)>>1;
        }else{
            // linear search if bisection failed, can only happen if there are very few or no keframes between min/max
            pos=pos_min;
        }
        if(pos <= pos_min)
            pos= pos_min + 1;
        else if(pos > pos_limit)
            pos= pos_limit;
        start_pos= pos;

        ts = read_timestamp(s, stream_index, &pos, INT64_MAX); //may pass pos_limit instead of -1
        if(pos == pos_max)
            no_change++;
        else
            no_change=0;
#ifdef DEBUG_SEEK
av_log(s, AV_LOG_DEBUG, "%Ld %Ld %Ld / %Ld %Ld %Ld target:%Ld limit:%Ld start:%Ld noc:%d\n", pos_min, pos, pos_max, ts_min, ts, ts_max, target_ts, pos_limit, start_pos, no_change);
#endif
        assert(ts != AV_NOPTS_VALUE);
        if (target_ts < ts) {
            pos_limit = start_pos - 1;
            pos_max = pos;
            ts_max = ts;
        } else {
            pos_min = pos;
            ts_min = ts;
            /* check if we are lucky */
            if (target_ts == ts)
                break;
        }
    }
    
    pos = pos_min;
#ifdef DEBUG_SEEK
    pos_min = pos;
    ts_min = read_timestamp(s, stream_index, &pos_min, INT64_MAX);
    pos_min++;
    ts_max = read_timestamp(s, stream_index, &pos_min, INT64_MAX);
    av_log(s, AV_LOG_DEBUG, "pos=0x%llx %lld<=%lld<=%lld\n", 
           pos, ts_min, target_ts, ts_max);
#endif
    /* do the seek */
    url_fseek(&s->pb, pos, SEEK_SET);

    nut->written_packet_size= -1;
    for(i=0; i<s->nb_streams; i++)
        nut->stream[i].last_sync_pos= pos;

    return 0;
}

static int nut_read_close(AVFormatContext *s)
{
    NUTContext *nut = s->priv_data;
    int i;

    for(i=0;i<s->nb_streams;i++) {
        av_freep(&s->streams[i]->codec.extradata);
    }
    av_freep(&nut->stream);

    return 0;
}

static AVInputFormat nut_iformat = {
    "nut",
    "nut format",
    sizeof(NUTContext),
    nut_probe,
    nut_read_header,
    nut_read_packet,
    nut_read_close,
    nut_read_seek,
    .extensions = "nut",
};

#ifdef CONFIG_ENCODERS
static AVOutputFormat nut_oformat = {
    "nut",
    "nut format",
    "video/x-nut",
    "nut",
    sizeof(NUTContext),
#ifdef CONFIG_VORBIS
    CODEC_ID_VORBIS,
#elif defined(CONFIG_MP3LAME)
    CODEC_ID_MP3,
#else
    CODEC_ID_MP2, /* AC3 needs liba52 decoder */
#endif
    CODEC_ID_MPEG4,
    nut_write_header,
    nut_write_packet,
    nut_write_trailer,
};
#endif //CONFIG_ENCODERS

int nut_init(void)
{
    av_register_input_format(&nut_iformat);
#ifdef CONFIG_ENCODERS
    av_register_output_format(&nut_oformat);
#endif //CONFIG_ENCODERS
    return 0;
}