nuv.c

/*****************************************************************************
 * nuv.c:
 *****************************************************************************
 * Copyright (C) 2005 the VideoLAN team
 * $Id: $
 *
 * Authors: Laurent Aimar <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#include <vlc/vlc.h>
#include <vlc/input.h>

/* TODO:
 *  - complete support (add support for rtjpeg and raw)
 *  - better seek support (to key frame)
 *  - control GET_LENGTH (harder, unless we have an extended header+index)
 *  - test
 */

/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
static int  Open  ( vlc_object_t * );
static void Close ( vlc_object_t * );

vlc_module_begin();
    set_category( CAT_INPUT );
    set_subcategory( SUBCAT_INPUT_DEMUX );
    set_description( _("Nuv demuxer") );
    set_capability( "demux2", 145 );
    set_callbacks( Open, Close );
    add_shortcut( "nuv" );
vlc_module_end();

/*****************************************************************************
 * Local prototypes
 *****************************************************************************/
static int Demux  ( demux_t * );
static int Control( demux_t *, int, va_list );

/* */
typedef struct
{
    int64_t i_time;
    int64_t i_offset;

} demux_index_entry_t;

typedef struct
{
    int i_idx;
    int i_idx_max;

    demux_index_entry_t *idx;
} demux_index_t;


static void demux_IndexInit( demux_index_t * );
static void demux_IndexClean( demux_index_t * );
static void demux_IndexAppend( demux_index_t *,
                               int64_t i_time, int64_t i_offset );
/* Convert a time into offset */
static int64_t demux_IndexConvertTime( demux_index_t *, int64_t i_time );
/* Find the nearest offset in the index */
static int64_t demux_IndexFindOffset( demux_index_t *, int64_t i_offset );


/* */
typedef struct
{
    char id[12];       /* "NuppelVideo\0" or "MythTVVideo\0" */
    char version[5];    /* "x.xx\0" */

    int  i_width;
    int  i_height;
    int  i_width_desired;
    int  i_height_desired;

    char i_mode;            /* P progressive, I interlaced */

    double  d_aspect;       /* 1.0 squared pixel */
    double  d_fps;

    int     i_video_blocks; /* 0 no video, -1 unknown */
    int     i_audio_blocks;
    int     i_text_blocks;

    int     i_keyframe_distance;

} header_t;

typedef struct
{
    char i_type;        /* A: audio, V: video, S: sync; T: test
                           R: Seekpoint (string:RTjjjjjjjj)
                           D: Extra data for codec */
    char i_compression; /* V: 0 uncompressed
                              1 RTJpeg
                              2 RTJpeg+lzo
                              N black frame
                              L copy last
                           A: 0 uncompressed (44100 1-bits, 2ch)
                              1 lzo
                              2 layer 2
                              3 layer 3
                              F flac
                              S shorten
                              N null frame loudless
                              L copy last
                            S: B audio and vdeo sync point
                               A audio sync info (timecode == effective
                                    dsp frequency*100)
                               V next video sync (timecode == next video
                                    frame num)
                               S audio,video,text correlation */
    char i_keyframe;    /* 0 keyframe, else no no key frame */
    uint8_t i_filters;  /* 0x01: gauss 5 pixel (8,2,2,2,2)/16
                           0x02: gauss 5 pixel (8,1,1,1,1)/12
                           0x04: cartoon filter */

    int i_timecode;     /* ms */

    int i_length;       /* V,A,T: length of following data
                           S: length of packet correl */
} frame_header_t;

/* FIXME Not sure of this one */
typedef struct
{
    int             i_version;
    vlc_fourcc_t    i_video_fcc;

    vlc_fourcc_t    i_audio_fcc;
    int             i_audio_sample_rate;
    int             i_audio_bits_per_sample;
    int             i_audio_channels;
    int             i_audio_compression_ratio;
    int             i_audio_quality;
    int             i_rtjpeg_quality;
    int             i_rtjpeg_luma_filter;
    int             i_rtjpeg_chroma_filter;
    int             i_lavc_bitrate;
    int             i_lavc_qmin;
    int             i_lavc_qmax;
    int             i_lavc_maxqdiff;
    int64_t         i_seekable_offset;
    int64_t         i_keyframe_adjust_offset;

} extended_header_t;

struct demux_sys_t
{
    header_t          hdr;
    extended_header_t exh;

    int64_t     i_pcr;
    es_out_id_t *p_es_video;
    int         i_extra_f;
    uint8_t     *p_extra_f;

    es_out_id_t *p_es_audio;

    /* index */
    demux_index_t idx;
};

static int HeaderLoad( demux_t *, header_t *h );
static int FrameHeaderLoad( demux_t *, frame_header_t *h );
static int ExtendedHeaderLoad( demux_t *, extended_header_t *h );

/*****************************************************************************
 * Open: initializes ES structures
 *****************************************************************************/
static int Open( vlc_object_t * p_this )
{
    demux_t     *p_demux = (demux_t*)p_this;
    demux_sys_t *p_sys;
    uint8_t     *p_peek;
    frame_header_t fh;
    vlc_bool_t  b_extended;

    /* Check id */
    if( stream_Peek( p_demux->s, &p_peek, 12 ) != 12 ||
        ( strncmp( (char *)p_peek, "MythTVVideo", 11 ) &&
          strncmp( (char *)p_peek, "NuppelVideo", 11 ) ) )
        return VLC_EGENERIC;

    p_sys = malloc( sizeof( demux_sys_t ) );
    memset( p_sys, 0, sizeof( demux_sys_t ) );
    p_sys->p_es_video = NULL;
    p_sys->p_es_audio = NULL;
    p_sys->p_extra_f = NULL;
    p_sys->i_pcr = -1;
    demux_IndexInit( &p_sys->idx );

    if( HeaderLoad( p_demux, &p_sys->hdr ) )
        goto error;

    /* Load 'D' */
    if( FrameHeaderLoad( p_demux, &fh ) || fh.i_type != 'D' )
        goto error;
    if( fh.i_length > 0 )
    {
        if( fh.i_compression == 'F' )
        {
            /* ffmpeg extra data */
            p_sys->i_extra_f = fh.i_length;
            p_sys->p_extra_f = malloc( fh.i_length );
            if( stream_Read( p_demux->s,
                             p_sys->p_extra_f, fh.i_length ) != fh.i_length )
                goto error;
        }
        else
        {
            /* TODO handle rtjpeg */
            msg_Warn( p_demux, "unsupported 'D' frame (c=%c)", fh.i_compression );
            if( stream_Read( p_demux->s, NULL, fh.i_length ) != fh.i_length )
                goto error;
        }
    }

    /* Check and load extented */
    if( stream_Peek( p_demux->s, &p_peek, 1 ) != 1 )
        goto error;
    if( p_peek[0] == 'X' )
    {
        b_extended = VLC_TRUE;

        if( FrameHeaderLoad( p_demux, &fh ) )
            goto error;
        if( fh.i_length != 512 )
            goto error;

        if( ExtendedHeaderLoad( p_demux, &p_sys->exh ) )
            goto error;

    }
    else
    {
        b_extended = VLC_FALSE;

        /* XXX: for now only file with extended chunk are supported
         * why: because else we need to have support for rtjpeg+stupid nuv shit */
        msg_Err( p_demux, "incomplete NUV support (upload samples)" );
        goto error;
    }

    /* Create audio/video (will work only with extended header and audio=mp3 */
    if( p_sys->hdr.i_video_blocks != 0 )
    {
        es_format_t fmt;

        es_format_Init( &fmt, VIDEO_ES, p_sys->exh.i_video_fcc );
        fmt.video.i_width = p_sys->hdr.i_width;
        fmt.video.i_height = p_sys->hdr.i_height;
        fmt.i_extra = p_sys->i_extra_f;
        fmt.p_extra = p_sys->p_extra_f;

        p_sys->p_es_video = es_out_Add( p_demux->out, &fmt );
    }
    if( p_sys->hdr.i_audio_blocks != 0 )
    {
        es_format_t fmt;

        es_format_Init( &fmt, AUDIO_ES, VLC_FOURCC('m','p','g','a') );
        fmt.audio.i_rate = p_sys->exh.i_audio_sample_rate;
        fmt.audio.i_bitspersample = p_sys->exh.i_audio_bits_per_sample;

        p_sys->p_es_audio = es_out_Add( p_demux->out, &fmt );
    }
    if( p_sys->hdr.i_text_blocks != 0 )
    {
        msg_Warn( p_demux, "text not yet supported (upload samples)" );
    }


    /* Fill p_demux fields */
    p_demux->pf_demux = Demux;
    p_demux->pf_control = Control;
    p_demux->p_sys = p_sys;

    return VLC_SUCCESS;

error:
    msg_Warn( p_demux, "cannot load Nuv file" );
    free( p_sys );
    return VLC_EGENERIC;
}

/*****************************************************************************
 * Close: frees unused data
 *****************************************************************************/
static void Close( vlc_object_t * p_this )
{
    demux_t        *p_demux = (demux_t*)p_this;
    demux_sys_t    *p_sys = p_demux->p_sys;

    if( p_sys->p_extra_f )
        free( p_sys->p_extra_f );
    demux_IndexClean( &p_sys->idx );
    free( p_sys );
}

/*****************************************************************************
 * Demux: reads and demuxes data packets
 *****************************************************************************
 * Returns -1 in case of error, 0 in case of EOF, 1 otherwise
 *****************************************************************************/
static int Demux( demux_t *p_demux )
{
    demux_sys_t *p_sys = p_demux->p_sys;
    frame_header_t fh;
    block_t *p_data;

    for( ;; )
    {
        if( p_demux->b_die )
            return -1;

        if( FrameHeaderLoad( p_demux, &fh ) )
            return 0;

        if( fh.i_type == 'A' || fh.i_type == 'V' )
            break;

        /* TODO add support for some block type */

        if( fh.i_type != 'R' )
        {
            stream_Read( p_demux->s, NULL, fh.i_length );
        }
    }

    /* */
    p_data = stream_Block( p_demux->s, fh.i_length );
    p_data->i_dts = (int64_t)fh.i_timecode * 1000;
    p_data->i_pts = (fh.i_type == 'V') ? 0 : p_data->i_dts;

    /* */
    demux_IndexAppend( &p_sys->idx, p_data->i_dts, stream_Tell(p_demux->s) );

    /* */
    if( p_data->i_dts > p_sys->i_pcr )
    {
        p_sys->i_pcr = p_data->i_dts;
        es_out_Control( p_demux->out, ES_OUT_SET_PCR, p_sys->i_pcr );
    }

    if( fh.i_type == 'A' && p_sys->p_es_audio )
    {
        if( fh.i_compression == '3' )
            es_out_Send( p_demux->out, p_sys->p_es_audio, p_data );
        else
        {
            msg_Dbg( p_demux, "unsupported compression %c for audio (upload samples)", fh.i_compression );
            block_Release( p_data );
        }
    }
    else if( fh.i_type == 'V' && p_sys->p_es_video )
    {
        if( fh.i_compression >= '4' )
            es_out_Send( p_demux->out, p_sys->p_es_video, p_data );
        else
        {
            msg_Dbg( p_demux, "unsupported compression %c for video (upload samples)", fh.i_compression );
            block_Release( p_data );
        }
    }
    else
    {
        block_Release( p_data );
    }

    return 1;
}

/*****************************************************************************
 * Control:
 *****************************************************************************/
static int Control( demux_t *p_demux, int i_query, va_list args )
{
    demux_sys_t *p_sys  = p_demux->p_sys;

    double   f, *pf;
    int64_t i64, *pi64;

    switch( i_query )
    {

        case DEMUX_GET_POSITION:
            pf = (double*)va_arg( args, double * );
            i64 = stream_Size( p_demux->s );
            if( i64 > 0 )
                *pf = (double)stream_Tell( p_demux->s ) / (double)i64;
            else
                *pf = 0.0;
            return VLC_SUCCESS;

        case DEMUX_SET_POSITION:
        {
            int64_t i_pos;

            f = (double)va_arg( args, double );
            i_pos = stream_Size( p_demux->s ) * f;

            i64 = demux_IndexFindOffset( &p_sys->idx, i_pos );

            p_sys->i_pcr = -1;

            if( i64 >= 0 )
                return stream_Seek( p_demux->s, i64 );

            if( p_sys->idx.i_idx > 0 )
            {
                if( stream_Seek( p_demux->s, p_sys->idx.idx[p_sys->idx.i_idx-1].i_offset ) )
                    return VLC_EGENERIC;
            }
            else
            {
                if( stream_Seek( p_demux->s, 0 ) )
                    return VLC_EGENERIC;
            }

            while( !p_demux->b_die )
            {
                frame_header_t fh;
                int64_t i_tell;

                if( ( i_tell = stream_Tell( p_demux->s ) ) >= i_pos )
                    break;

                if( FrameHeaderLoad( p_demux, &fh ) )
                    return VLC_EGENERIC;

                if( fh.i_type == 'A' || fh.i_type == 'V' )
                    demux_IndexAppend( &p_sys->idx,(int64_t)fh.i_timecode*1000, i_tell );

                if( fh.i_type != 'R' )
                    stream_Read( p_demux->s, NULL, fh.i_length );
            }
            return VLC_SUCCESS;
        }


        case DEMUX_GET_TIME:
            pi64 = (int64_t*)va_arg( args, int64_t * );
            *pi64 = p_sys->i_pcr >= 0 ? p_sys->i_pcr : 0;
            return VLC_SUCCESS;

        case DEMUX_SET_TIME:
        {
            int64_t i_pos;
            i64 = (int64_t)va_arg( args, int64_t );

            i_pos = demux_IndexConvertTime( &p_sys->idx, i64 );
            if( i_pos < 0 )
                return VLC_EGENERIC;

            if( stream_Seek( p_demux->s, i_pos ) )
                return VLC_EGENERIC;

            p_sys->i_pcr = -1;

            while( !p_demux->b_die )
            {
                frame_header_t fh;

                if( FrameHeaderLoad( p_demux, &fh ) )
                    return VLC_EGENERIC;

                if( fh.i_type == 'A' || fh.i_type == 'V' )
                {
                    int64_t i_time = (int64_t)fh.i_timecode*1000;
                    int64_t i_tell = stream_Tell(p_demux->s)-12;

                    demux_IndexAppend( &p_sys->idx, i_time, i_tell );

                    if( i_time >= i64 )
                        return stream_Seek( p_demux->s, i_tell );
                }
                if( fh.i_type != 'R' )
                    stream_Read( p_demux->s, NULL, fh.i_length );
            }
            return VLC_SUCCESS;
        }

        case DEMUX_GET_LENGTH:
            pi64 = (int64_t*)va_arg( args, int64_t * );
            return VLC_EGENERIC;

        case DEMUX_GET_FPS:
            pf = (double*)va_arg( args, double * );
            *pf = p_sys->hdr.d_fps;
            return VLC_SUCCESS;

        case DEMUX_GET_META:
        default:
            return VLC_EGENERIC;

    }
}

/*****************************************************************************
 *
 *****************************************************************************/
static inline void GetDoubleLE( double *pd, void *src )
{
    /* FIXME works only if sizeof(double) == 8 */
#ifdef WORDS_BIGENDIAN
    uint8_t *p = (uint8_t*)pd, *q = (uint8_t*)src;
    int i;
    for( i = 0; i < 8; i++ )
        p[i] = q[7-i];
#else
    memcpy( pd, src, 8 );
#endif
}

/* HeaderLoad:
 */
static int HeaderLoad( demux_t *p_demux, header_t *h )
{
    uint8_t buffer[72];

    if( stream_Read( p_demux->s, buffer, 72 ) != 72 )
        return VLC_EGENERIC;

    /* XXX: they are alignment to take care of (another broken format) */
    memcpy( h->id,      &buffer[ 0], 12 );
    memcpy( h->version, &buffer[12], 5 );
    h->i_width = GetDWLE( &buffer[20] );
    h->i_height = GetDWLE( &buffer[24] );
    h->i_width_desired = GetDWLE( &buffer[28] );
    h->i_height_desired = GetDWLE( &buffer[32] );
    h->i_mode = buffer[36];
    GetDoubleLE( &h->d_aspect, &buffer[40] );
    GetDoubleLE( &h->d_fps, &buffer[48] );
    h->i_video_blocks = GetDWLE( &buffer[56] );
    h->i_audio_blocks = GetDWLE( &buffer[60] );
    h->i_text_blocks = GetDWLE( &buffer[64] );
    h->i_keyframe_distance = GetDWLE( &buffer[68] );
#if 0
    msg_Dbg( p_demux, "nuv: h=%s v=%s %dx%d a=%f fps=%f v=%d a=%d t=%d kfd=%d",
             h->id, h->version, h->i_width, h->i_height, h->d_aspect,
             h->d_fps, h->i_video_blocks, h->i_audio_blocks, h->i_text_blocks,
             h->i_keyframe_distance );
#endif
    return VLC_SUCCESS;
}

/* FrameHeaderLoad:
 */
static int FrameHeaderLoad( demux_t *p_demux, frame_header_t *h )
{
    uint8_t buffer[12];

    if( stream_Read( p_demux->s, buffer, 12 ) != 12 )
        return VLC_EGENERIC;

    h->i_type = buffer[0];
    h->i_compression = buffer[1];
    h->i_keyframe = buffer[2];
    h->i_filters = buffer[3];

    h->i_timecode = GetDWLE( &buffer[4] );
    h->i_length = GetDWLE( &buffer[8] );
#if 0
    msg_Dbg( p_demux, "frame hdr: t=%c c=%c k=%d f=0x%x timecode=%d l=%d",
             h->i_type,
             h->i_compression ? h->i_compression : ' ',
             h->i_keyframe ? h->i_keyframe : ' ',
             h->i_filters,
             h->i_timecode, h->i_length );
#endif
    return VLC_SUCCESS;
}

static int ExtendedHeaderLoad( demux_t *p_demux, extended_header_t *h )
{
    uint8_t buffer[512];

    if( stream_Read( p_demux->s, buffer, 512 ) != 512 )
        return VLC_EGENERIC;

    h->i_version = GetDWLE( &buffer[0] );
    h->i_video_fcc = VLC_FOURCC( buffer[4], buffer[5], buffer[6], buffer[7] );
    h->i_audio_fcc = VLC_FOURCC( buffer[8], buffer[9], buffer[10], buffer[11] );
    h->i_audio_sample_rate = GetDWLE( &buffer[12] );
    h->i_audio_bits_per_sample = GetDWLE( &buffer[16] );
    h->i_audio_channels = GetDWLE( &buffer[20] );
    h->i_audio_compression_ratio = GetDWLE( &buffer[24] );
    h->i_audio_quality = GetDWLE( &buffer[28] );
    h->i_rtjpeg_quality = GetDWLE( &buffer[32] );
    h->i_rtjpeg_luma_filter = GetDWLE( &buffer[36] );
    h->i_rtjpeg_chroma_filter = GetDWLE( &buffer[40] );
    h->i_lavc_bitrate = GetDWLE( &buffer[44] );
    h->i_lavc_qmin = GetDWLE( &buffer[48] );
    h->i_lavc_qmin = GetDWLE( &buffer[52] );
    h->i_lavc_maxqdiff = GetDWLE( &buffer[56] );
    h->i_seekable_offset = GetQWLE( &buffer[60] );
    h->i_keyframe_adjust_offset= GetQWLE( &buffer[68] );
#if 0
    msg_Dbg( p_demux, "ex hdr: v=%d vffc=%4.4s afcc=%4.4s %dHz %dbits ach=%d acr=%d aq=%d"
                      "rtjpeg q=%d lf=%d lc=%d lavc br=%d qmin=%d qmax=%d maxqdiff=%d seekableoff=%lld keyfao=%lld",
             h->i_version,
             (char*)&h->i_video_fcc,
             (char*)&h->i_audio_fcc, h->i_audio_sample_rate, h->i_audio_bits_per_sample, h->i_audio_channels,
             h->i_audio_compression_ratio, h->i_audio_quality,
             h->i_rtjpeg_quality, h->i_rtjpeg_luma_filter, h->i_rtjpeg_chroma_filter,
             h->i_lavc_bitrate, h->i_lavc_qmin, h->i_lavc_qmax, h->i_lavc_maxqdiff,
             h->i_seekable_offset, h->i_keyframe_adjust_offset );
#endif
    return VLC_SUCCESS;
}

/*****************************************************************************/
#define DEMUX_INDEX_SIZE_MAX (100000)
static void demux_IndexInit( demux_index_t *p_idx )
{
    p_idx->i_idx = 0;
    p_idx->i_idx_max = 0;
    p_idx->idx = NULL;
}
static void demux_IndexClean( demux_index_t *p_idx )
{
    if( p_idx->idx )
    {
        free( p_idx->idx );
        p_idx->idx = NULL;
    }
}
static void demux_IndexAppend( demux_index_t *p_idx,
                               int64_t i_time, int64_t i_offset )
{
    /* Be sure to append new entry (we don't insert point) */
    if( p_idx->i_idx > 0 && p_idx->idx[p_idx->i_idx-1].i_time >= i_time )
        return;

    /* */
    if( p_idx->i_idx >= p_idx->i_idx_max )
    {
        if( p_idx->i_idx >= DEMUX_INDEX_SIZE_MAX )
        {
            /* Avoid too big index */
            const int64_t i_length = p_idx->idx[p_idx->i_idx-1].i_time -
                                                        p_idx->idx[0].i_time;
            const int i_count = DEMUX_INDEX_SIZE_MAX/2;
            int i, j;

            /* We try to reduce the resolution of the index by a factor 2 */
            for( i = 1, j = 1; i < p_idx->i_idx; i++ )
            {
                if( p_idx->idx[i].i_time < j * i_length / i_count )
                    continue;

                p_idx->idx[j++] = p_idx->idx[i];
            }
            p_idx->i_idx = j;

            if( p_idx->i_idx > 3 * DEMUX_INDEX_SIZE_MAX / 4 )
            {
                /* We haven't created enough space
                 * (This method won't create a good index but work for sure) */
                for( i = 0; i < p_idx->i_idx/2; i++ )
                    p_idx->idx[i] = p_idx->idx[2*i];
                p_idx->i_idx /= 2;
            }
        }
        else
        {
            p_idx->i_idx_max += 1000;
            p_idx->idx = realloc( p_idx->idx,
                                  p_idx->i_idx_max*sizeof(demux_index_entry_t));
        }
    }

    /* */
    p_idx->idx[p_idx->i_idx].i_time = i_time;
    p_idx->idx[p_idx->i_idx].i_offset = i_offset;

    p_idx->i_idx++;
}
static int64_t demux_IndexConvertTime( demux_index_t *p_idx, int64_t i_time )
{
    int i_min = 0;
    int i_max = p_idx->i_idx-1;

    /* Empty index */
    if( p_idx->i_idx <= 0 )
        return -1;

    /* Special border case */
    if( i_time <= p_idx->idx[0].i_time )
        return p_idx->idx[0].i_offset;
    if( i_time >= p_idx->idx[i_max].i_time )
        return p_idx->idx[i_max].i_offset;

    /* Dicho */
    for( ;; )
    {
        int i_med;

        if( i_max - i_min <= 1 )
            break;

        i_med = (i_min+i_max)/2;
        if( p_idx->idx[i_med].i_time < i_time )
            i_min = i_med;
        else if( p_idx->idx[i_med].i_time > i_time )
            i_max = i_med;
        else
            return p_idx->idx[i_med].i_offset;
    }

    /* return nearest in time */
    if( i_time - p_idx->idx[i_min].i_time < p_idx->idx[i_max].i_time - i_time )
        return p_idx->idx[i_min].i_offset;
    else
        return p_idx->idx[i_max].i_offset;
}


static int64_t demux_IndexFindOffset( demux_index_t *p_idx, int64_t i_offset )
{
    int i_min = 0;
    int i_max = p_idx->i_idx-1;

    /* Empty index */
    if( p_idx->i_idx <= 0 )
        return -1;

    /* Special border case */
    if( i_offset <= p_idx->idx[0].i_offset )
        return p_idx->idx[0].i_offset;
    if( i_offset == p_idx->idx[i_max].i_offset )
        return p_idx->idx[i_max].i_offset;
    if( i_offset > p_idx->idx[i_max].i_offset )
        return -1;

    /* Dicho */
    for( ;; )
    {
        int i_med;

        if( i_max - i_min <= 1 )
            break;

        i_med = (i_min+i_max)/2;
        if( p_idx->idx[i_med].i_offset < i_offset )
            i_min = i_med;
        else if( p_idx->idx[i_med].i_offset > i_offset )
            i_max = i_med;
        else
            return p_idx->idx[i_med].i_offset;
    }

    /* return nearest */
    if( i_offset - p_idx->idx[i_min].i_offset < p_idx->idx[i_max].i_offset - i_offset )
        return p_idx->idx[i_min].i_offset;
    else
        return p_idx->idx[i_max].i_offset;
}

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