libavformat/dv.c
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00001 /*
00002  * General DV muxer/demuxer
00003  * Copyright (c) 2003 Roman Shaposhnik
00004  *
00005  * Many thanks to Dan Dennedy <dan@dennedy.org> for providing wealth
00006  * of DV technical info.
00007  *
00008  * Raw DV format
00009  * Copyright (c) 2002 Fabrice Bellard
00010  *
00011  * 50 Mbps (DVCPRO50) and 100 Mbps (DVCPRO HD) support
00012  * Copyright (c) 2006 Daniel Maas <dmaas@maasdigital.com>
00013  * Funded by BBC Research & Development
00014  *
00015  * This file is part of FFmpeg.
00016  *
00017  * FFmpeg is free software; you can redistribute it and/or
00018  * modify it under the terms of the GNU Lesser General Public
00019  * License as published by the Free Software Foundation; either
00020  * version 2.1 of the License, or (at your option) any later version.
00021  *
00022  * FFmpeg is distributed in the hope that it will be useful,
00023  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00024  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00025  * Lesser General Public License for more details.
00026  *
00027  * You should have received a copy of the GNU Lesser General Public
00028  * License along with FFmpeg; if not, write to the Free Software
00029  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00030  */
00031 #include <time.h>
00032 #include "avformat.h"
00033 #include "internal.h"
00034 #include "libavcodec/dvdata.h"
00035 #include "libavutil/intreadwrite.h"
00036 #include "libavutil/mathematics.h"
00037 #include "dv.h"
00038 #include "libavutil/avassert.h"
00039 
00040 struct DVDemuxContext {
00041     const DVprofile*  sys;    /* Current DV profile. E.g.: 525/60, 625/50 */
00042     AVFormatContext*  fctx;
00043     AVStream*         vst;
00044     AVStream*         ast[4];
00045     AVPacket          audio_pkt[4];
00046     uint8_t           audio_buf[4][8192];
00047     int               ach;
00048     int               frames;
00049     uint64_t          abytes;
00050 };
00051 
00052 static inline uint16_t dv_audio_12to16(uint16_t sample)
00053 {
00054     uint16_t shift, result;
00055 
00056     sample = (sample < 0x800) ? sample : sample | 0xf000;
00057     shift  = (sample & 0xf00) >> 8;
00058 
00059     if (shift < 0x2 || shift > 0xd) {
00060         result = sample;
00061     } else if (shift < 0x8) {
00062         shift--;
00063         result = (sample - (256 * shift)) << shift;
00064     } else {
00065         shift = 0xe - shift;
00066         result = ((sample + ((256 * shift) + 1)) << shift) - 1;
00067     }
00068 
00069     return result;
00070 }
00071 
00072 /*
00073  * This is the dumbest implementation of all -- it simply looks at
00074  * a fixed offset and if pack isn't there -- fails. We might want
00075  * to have a fallback mechanism for complete search of missing packs.
00076  */
00077 static const uint8_t* dv_extract_pack(uint8_t* frame, enum dv_pack_type t)
00078 {
00079     int offs;
00080 
00081     switch (t) {
00082     case dv_audio_source:
00083         offs = (80*6 + 80*16*3 + 3);
00084         break;
00085     case dv_audio_control:
00086         offs = (80*6 + 80*16*4 + 3);
00087         break;
00088     case dv_video_control:
00089         offs = (80*5 + 48 + 5);
00090         break;
00091     case dv_timecode:
00092         offs = (80*1 + 3 + 3);
00093         break;
00094     default:
00095         return NULL;
00096     }
00097 
00098     return frame[offs] == t ? &frame[offs] : NULL;
00099 }
00100 
00101 /*
00102  * There's a couple of assumptions being made here:
00103  * 1. By default we silence erroneous (0x8000/16bit 0x800/12bit) audio samples.
00104  *    We can pass them upwards when libavcodec will be ready to deal with them.
00105  * 2. We don't do software emphasis.
00106  * 3. Audio is always returned as 16bit linear samples: 12bit nonlinear samples
00107  *    are converted into 16bit linear ones.
00108  */
00109 static int dv_extract_audio(uint8_t* frame, uint8_t* ppcm[4],
00110                             const DVprofile *sys)
00111 {
00112     int size, chan, i, j, d, of, smpls, freq, quant, half_ch;
00113     uint16_t lc, rc;
00114     const uint8_t* as_pack;
00115     uint8_t *pcm, ipcm;
00116 
00117     as_pack = dv_extract_pack(frame, dv_audio_source);
00118     if (!as_pack)    /* No audio ? */
00119         return 0;
00120 
00121     smpls =  as_pack[1] & 0x3f;       /* samples in this frame - min. samples */
00122     freq  = (as_pack[4] >> 3) & 0x07; /* 0 - 48kHz, 1 - 44,1kHz, 2 - 32kHz */
00123     quant =  as_pack[4] & 0x07;       /* 0 - 16bit linear, 1 - 12bit nonlinear */
00124 
00125     if (quant > 1)
00126         return -1; /* unsupported quantization */
00127 
00128     if (freq >= FF_ARRAY_ELEMS(dv_audio_frequency))
00129         return AVERROR_INVALIDDATA;
00130 
00131     size = (sys->audio_min_samples[freq] + smpls) * 4; /* 2ch, 2bytes */
00132     half_ch = sys->difseg_size / 2;
00133 
00134     /* We work with 720p frames split in half, thus even frames have
00135      * channels 0,1 and odd 2,3. */
00136     ipcm = (sys->height == 720 && !(frame[1] & 0x0C)) ? 2 : 0;
00137 
00138     /* for each DIF channel */
00139     for (chan = 0; chan < sys->n_difchan; chan++) {
00140         av_assert0(ipcm<4);
00141         /* next stereo channel (50Mbps and 100Mbps only) */
00142         pcm = ppcm[ipcm++];
00143         if (!pcm)
00144             break;
00145         /* for each DIF segment */
00146         for (i = 0; i < sys->difseg_size; i++) {
00147             frame += 6 * 80; /* skip DIF segment header */
00148             if (quant == 1 && i == half_ch) {
00149                 /* next stereo channel (12bit mode only) */
00150                 av_assert0(ipcm<4);
00151                 pcm = ppcm[ipcm++];
00152                 if (!pcm)
00153                     break;
00154             }
00155 
00156             /* for each AV sequence */
00157             for (j = 0; j < 9; j++) {
00158                 for (d = 8; d < 80; d += 2) {
00159                     if (quant == 0) {  /* 16bit quantization */
00160                         of = sys->audio_shuffle[i][j] + (d - 8) / 2 * sys->audio_stride;
00161                         if (of*2 >= size)
00162                             continue;
00163 
00164                         pcm[of*2]   = frame[d+1]; // FIXME: maybe we have to admit
00165                         pcm[of*2+1] = frame[d];   //        that DV is a big-endian PCM
00166                         if (pcm[of*2+1] == 0x80 && pcm[of*2] == 0x00)
00167                             pcm[of*2+1] = 0;
00168                     } else {           /* 12bit quantization */
00169                         lc = ((uint16_t)frame[d]   << 4) |
00170                              ((uint16_t)frame[d+2] >> 4);
00171                         rc = ((uint16_t)frame[d+1] << 4) |
00172                              ((uint16_t)frame[d+2] & 0x0f);
00173                         lc = (lc == 0x800 ? 0 : dv_audio_12to16(lc));
00174                         rc = (rc == 0x800 ? 0 : dv_audio_12to16(rc));
00175 
00176                         of = sys->audio_shuffle[i%half_ch][j] + (d - 8) / 3 * sys->audio_stride;
00177                         if (of*2 >= size)
00178                             continue;
00179 
00180                         pcm[of*2]   = lc & 0xff; // FIXME: maybe we have to admit
00181                         pcm[of*2+1] = lc >> 8;   //        that DV is a big-endian PCM
00182                         of = sys->audio_shuffle[i%half_ch+half_ch][j] +
00183                             (d - 8) / 3 * sys->audio_stride;
00184                         pcm[of*2]   = rc & 0xff; // FIXME: maybe we have to admit
00185                         pcm[of*2+1] = rc >> 8;   //        that DV is a big-endian PCM
00186                         ++d;
00187                     }
00188                 }
00189 
00190                 frame += 16 * 80; /* 15 Video DIFs + 1 Audio DIF */
00191             }
00192         }
00193     }
00194 
00195     return size;
00196 }
00197 
00198 static int dv_extract_audio_info(DVDemuxContext* c, uint8_t* frame)
00199 {
00200     const uint8_t* as_pack;
00201     int freq, stype, smpls, quant, i, ach;
00202 
00203     as_pack = dv_extract_pack(frame, dv_audio_source);
00204     if (!as_pack || !c->sys) {    /* No audio ? */
00205         c->ach = 0;
00206         return 0;
00207     }
00208 
00209     smpls =  as_pack[1] & 0x3f;       /* samples in this frame - min. samples */
00210     freq  = (as_pack[4] >> 3) & 0x07; /* 0 - 48kHz, 1 - 44,1kHz, 2 - 32kHz */
00211     stype = (as_pack[3] & 0x1f);      /* 0 - 2CH, 2 - 4CH, 3 - 8CH */
00212     quant =  as_pack[4] & 0x07;       /* 0 - 16bit linear, 1 - 12bit nonlinear */
00213 
00214     if (freq >= FF_ARRAY_ELEMS(dv_audio_frequency)) {
00215         av_log(c->fctx, AV_LOG_ERROR,
00216                "Unrecognized audio sample rate index (%d)\n", freq);
00217         return 0;
00218     }
00219 
00220     if (stype > 3) {
00221         av_log(c->fctx, AV_LOG_ERROR, "stype %d is invalid\n", stype);
00222         c->ach = 0;
00223         return 0;
00224     }
00225 
00226     /* note: ach counts PAIRS of channels (i.e. stereo channels) */
00227     ach = ((int[4]){  1,  0,  2,  4})[stype];
00228     if (ach == 1 && quant && freq == 2)
00229         ach = 2;
00230 
00231     /* Dynamic handling of the audio streams in DV */
00232     for (i = 0; i < ach; i++) {
00233        if (!c->ast[i]) {
00234            c->ast[i] = avformat_new_stream(c->fctx, NULL);
00235            if (!c->ast[i])
00236                break;
00237            avpriv_set_pts_info(c->ast[i], 64, 1, 30000);
00238            c->ast[i]->codec->codec_type = AVMEDIA_TYPE_AUDIO;
00239            c->ast[i]->codec->codec_id   = CODEC_ID_PCM_S16LE;
00240 
00241            av_init_packet(&c->audio_pkt[i]);
00242            c->audio_pkt[i].size         = 0;
00243            c->audio_pkt[i].data         = c->audio_buf[i];
00244            c->audio_pkt[i].stream_index = c->ast[i]->index;
00245            c->audio_pkt[i].flags       |= AV_PKT_FLAG_KEY;
00246        }
00247        c->ast[i]->codec->sample_rate = dv_audio_frequency[freq];
00248        c->ast[i]->codec->channels    = 2;
00249        c->ast[i]->codec->bit_rate    = 2 * dv_audio_frequency[freq] * 16;
00250        c->ast[i]->start_time         = 0;
00251     }
00252     c->ach = i;
00253 
00254     return (c->sys->audio_min_samples[freq] + smpls) * 4; /* 2ch, 2bytes */;
00255 }
00256 
00257 static int dv_extract_video_info(DVDemuxContext *c, uint8_t* frame)
00258 {
00259     const uint8_t* vsc_pack;
00260     AVCodecContext* avctx;
00261     int apt, is16_9;
00262     int size = 0;
00263 
00264     if (c->sys) {
00265         avctx = c->vst->codec;
00266 
00267         avpriv_set_pts_info(c->vst, 64, c->sys->time_base.num,
00268                         c->sys->time_base.den);
00269         avctx->time_base= c->sys->time_base;
00270         if (!avctx->width)
00271             avcodec_set_dimensions(avctx, c->sys->width, c->sys->height);
00272         avctx->pix_fmt = c->sys->pix_fmt;
00273 
00274         /* finding out SAR is a little bit messy */
00275         vsc_pack = dv_extract_pack(frame, dv_video_control);
00276         apt      = frame[4] & 0x07;
00277         is16_9   = (vsc_pack && ((vsc_pack[2] & 0x07) == 0x02 ||
00278                                 (!apt && (vsc_pack[2] & 0x07) == 0x07)));
00279         c->vst->sample_aspect_ratio = c->sys->sar[is16_9];
00280         avctx->bit_rate = av_rescale_q(c->sys->frame_size, (AVRational){8,1},
00281                                        c->sys->time_base);
00282         size = c->sys->frame_size;
00283     }
00284     return size;
00285 }
00286 
00287 static int bcd2int(uint8_t bcd)
00288 {
00289    int low  = bcd & 0xf;
00290    int high = bcd >> 4;
00291    if (low > 9 || high > 9)
00292        return -1;
00293    return low + 10*high;
00294 }
00295 
00296 static int dv_extract_timecode(DVDemuxContext* c, uint8_t* frame, char tc[32])
00297 {
00298     int hh, mm, ss, ff, drop_frame;
00299     const uint8_t *tc_pack;
00300 
00301     tc_pack = dv_extract_pack(frame, dv_timecode);
00302     if (!tc_pack)
00303         return 0;
00304 
00305     ff = bcd2int(tc_pack[1] & 0x3f);
00306     ss = bcd2int(tc_pack[2] & 0x7f);
00307     mm = bcd2int(tc_pack[3] & 0x7f);
00308     hh = bcd2int(tc_pack[4] & 0x3f);
00309     drop_frame = tc_pack[1] >> 6 & 0x1;
00310 
00311     if (ff < 0 || ss < 0 || mm < 0 || hh < 0)
00312         return -1;
00313 
00314     // For PAL systems, drop frame bit is replaced by an arbitrary
00315     // bit so its value should not be considered. Drop frame timecode
00316     // is only relevant for NTSC systems.
00317     if(c->sys->ltc_divisor == 25 || c->sys->ltc_divisor == 50) {
00318         drop_frame = 0;
00319     }
00320 
00321     snprintf(tc, 32, "%02d:%02d:%02d%c%02d",
00322              hh, mm, ss, drop_frame ? ';' : ':', ff);
00323     return 1;
00324 }
00325 
00326 /*
00327  * The following 3 functions constitute our interface to the world
00328  */
00329 
00330 DVDemuxContext* avpriv_dv_init_demux(AVFormatContext *s)
00331 {
00332     DVDemuxContext *c;
00333 
00334     c = av_mallocz(sizeof(DVDemuxContext));
00335     if (!c)
00336         return NULL;
00337 
00338     c->vst = avformat_new_stream(s, NULL);
00339     if (!c->vst) {
00340         av_free(c);
00341         return NULL;
00342     }
00343 
00344     c->sys  = NULL;
00345     c->fctx = s;
00346     memset(c->ast, 0, sizeof(c->ast));
00347     c->ach    = 0;
00348     c->frames = 0;
00349     c->abytes = 0;
00350 
00351     c->vst->codec->codec_type = AVMEDIA_TYPE_VIDEO;
00352     c->vst->codec->codec_id   = CODEC_ID_DVVIDEO;
00353     c->vst->codec->bit_rate   = 25000000;
00354     c->vst->start_time        = 0;
00355 
00356     return c;
00357 }
00358 
00359 int avpriv_dv_get_packet(DVDemuxContext *c, AVPacket *pkt)
00360 {
00361     int size = -1;
00362     int i;
00363 
00364     for (i = 0; i < c->ach; i++) {
00365        if (c->ast[i] && c->audio_pkt[i].size) {
00366            *pkt = c->audio_pkt[i];
00367            c->audio_pkt[i].size = 0;
00368            size = pkt->size;
00369            break;
00370        }
00371     }
00372 
00373     return size;
00374 }
00375 
00376 int avpriv_dv_produce_packet(DVDemuxContext *c, AVPacket *pkt,
00377                       uint8_t* buf, int buf_size, int64_t pos)
00378 {
00379     int size, i;
00380     uint8_t *ppcm[4] = {0};
00381 
00382     if (buf_size < DV_PROFILE_BYTES ||
00383         !(c->sys = avpriv_dv_frame_profile(c->sys, buf, buf_size)) ||
00384         buf_size < c->sys->frame_size) {
00385           return -1;   /* Broken frame, or not enough data */
00386     }
00387 
00388     /* Queueing audio packet */
00389     /* FIXME: in case of no audio/bad audio we have to do something */
00390     size = dv_extract_audio_info(c, buf);
00391     for (i = 0; i < c->ach; i++) {
00392        c->audio_pkt[i].pos  = pos;
00393        c->audio_pkt[i].size = size;
00394        c->audio_pkt[i].pts  = c->abytes * 30000*8 / c->ast[i]->codec->bit_rate;
00395        ppcm[i] = c->audio_buf[i];
00396     }
00397     if (c->ach)
00398         dv_extract_audio(buf, ppcm, c->sys);
00399 
00400     /* We work with 720p frames split in half, thus even frames have
00401      * channels 0,1 and odd 2,3. */
00402     if (c->sys->height == 720) {
00403         if (buf[1] & 0x0C) {
00404             c->audio_pkt[2].size = c->audio_pkt[3].size = 0;
00405         } else {
00406             c->audio_pkt[0].size = c->audio_pkt[1].size = 0;
00407             c->abytes += size;
00408         }
00409     } else {
00410         c->abytes += size;
00411     }
00412 
00413     /* Now it's time to return video packet */
00414     size = dv_extract_video_info(c, buf);
00415     av_init_packet(pkt);
00416     pkt->data         = buf;
00417     pkt->pos          = pos;
00418     pkt->size         = size;
00419     pkt->flags       |= AV_PKT_FLAG_KEY;
00420     pkt->stream_index = c->vst->id;
00421     pkt->pts          = c->frames;
00422 
00423     c->frames++;
00424 
00425     return size;
00426 }
00427 
00428 static int64_t dv_frame_offset(AVFormatContext *s, DVDemuxContext *c,
00429                               int64_t timestamp, int flags)
00430 {
00431     // FIXME: sys may be wrong if last dv_read_packet() failed (buffer is junk)
00432     const DVprofile* sys = avpriv_dv_codec_profile(c->vst->codec);
00433     int64_t offset;
00434     int64_t size = avio_size(s->pb) - s->data_offset;
00435     int64_t max_offset = ((size-1) / sys->frame_size) * sys->frame_size;
00436 
00437     offset = sys->frame_size * timestamp;
00438 
00439     if (size >= 0 && offset > max_offset) offset = max_offset;
00440     else if (offset < 0) offset = 0;
00441 
00442     return offset + s->data_offset;
00443 }
00444 
00445 void dv_offset_reset(DVDemuxContext *c, int64_t frame_offset)
00446 {
00447     c->frames= frame_offset;
00448     if (c->ach)
00449         c->abytes= av_rescale_q(c->frames, c->sys->time_base,
00450                                 (AVRational){8, c->ast[0]->codec->bit_rate});
00451     c->audio_pkt[0].size = c->audio_pkt[1].size = 0;
00452     c->audio_pkt[2].size = c->audio_pkt[3].size = 0;
00453 }
00454 
00455 /************************************************************
00456  * Implementation of the easiest DV storage of all -- raw DV.
00457  ************************************************************/
00458 
00459 typedef struct RawDVContext {
00460     DVDemuxContext* dv_demux;
00461     uint8_t         buf[DV_MAX_FRAME_SIZE];
00462 } RawDVContext;
00463 
00464 static int dv_read_timecode(AVFormatContext *s) {
00465     int ret;
00466     char timecode[32];
00467     int64_t pos = avio_tell(s->pb);
00468 
00469     // Read 3 DIF blocks: Header block and 2 Subcode blocks.
00470     int partial_frame_size = 3 * 80;
00471     uint8_t *partial_frame = av_mallocz(sizeof(*partial_frame) *
00472                                         partial_frame_size);
00473 
00474     RawDVContext *c = s->priv_data;
00475     ret = avio_read(s->pb, partial_frame, partial_frame_size);
00476     if (ret < 0)
00477         goto finish;
00478 
00479     if (ret < partial_frame_size) {
00480         ret = -1;
00481         goto finish;
00482     }
00483 
00484     ret = dv_extract_timecode(c->dv_demux, partial_frame, timecode);
00485     if (ret)
00486         av_dict_set(&s->metadata, "timecode", timecode, 0);
00487     else if (ret < 0)
00488         av_log(s, AV_LOG_ERROR, "Detected timecode is invalid");
00489 
00490 finish:
00491     av_free(partial_frame);
00492     avio_seek(s->pb, pos, SEEK_SET);
00493     return ret;
00494 }
00495 
00496 static int dv_read_header(AVFormatContext *s,
00497                           AVFormatParameters *ap)
00498 {
00499     unsigned state, marker_pos = 0;
00500     RawDVContext *c = s->priv_data;
00501 
00502     c->dv_demux = avpriv_dv_init_demux(s);
00503     if (!c->dv_demux)
00504         return -1;
00505 
00506     state = avio_rb32(s->pb);
00507     while ((state & 0xffffff7f) != 0x1f07003f) {
00508         if (url_feof(s->pb)) {
00509             av_log(s, AV_LOG_ERROR, "Cannot find DV header.\n");
00510             return -1;
00511         }
00512         if (state == 0x003f0700 || state == 0xff3f0700)
00513             marker_pos = avio_tell(s->pb);
00514         if (state == 0xff3f0701 && avio_tell(s->pb) - marker_pos == 80) {
00515             avio_seek(s->pb, -163, SEEK_CUR);
00516             state = avio_rb32(s->pb);
00517             break;
00518         }
00519         state = (state << 8) | avio_r8(s->pb);
00520     }
00521     AV_WB32(c->buf, state);
00522 
00523     if (avio_read(s->pb, c->buf + 4, DV_PROFILE_BYTES - 4) <= 0 ||
00524         avio_seek(s->pb, -DV_PROFILE_BYTES, SEEK_CUR) < 0)
00525         return AVERROR(EIO);
00526 
00527     c->dv_demux->sys = avpriv_dv_frame_profile(c->dv_demux->sys, c->buf, DV_PROFILE_BYTES);
00528     if (!c->dv_demux->sys) {
00529         av_log(s, AV_LOG_ERROR, "Can't determine profile of DV input stream.\n");
00530         return -1;
00531     }
00532 
00533     s->bit_rate = av_rescale_q(c->dv_demux->sys->frame_size, (AVRational){8,1},
00534                                c->dv_demux->sys->time_base);
00535 
00536     if (s->pb->seekable)
00537         dv_read_timecode(s);
00538 
00539     return 0;
00540 }
00541 
00542 
00543 static int dv_read_packet(AVFormatContext *s, AVPacket *pkt)
00544 {
00545     int size;
00546     RawDVContext *c = s->priv_data;
00547 
00548     size = avpriv_dv_get_packet(c->dv_demux, pkt);
00549 
00550     if (size < 0) {
00551         int64_t pos = avio_tell(s->pb);
00552         if (!c->dv_demux->sys)
00553             return AVERROR(EIO);
00554         size = c->dv_demux->sys->frame_size;
00555         if (avio_read(s->pb, c->buf, size) <= 0)
00556             return AVERROR(EIO);
00557 
00558         size = avpriv_dv_produce_packet(c->dv_demux, pkt, c->buf, size, pos);
00559     }
00560 
00561     return size;
00562 }
00563 
00564 static int dv_read_seek(AVFormatContext *s, int stream_index,
00565                        int64_t timestamp, int flags)
00566 {
00567     RawDVContext *r   = s->priv_data;
00568     DVDemuxContext *c = r->dv_demux;
00569     int64_t offset    = dv_frame_offset(s, c, timestamp, flags);
00570 
00571     if (avio_seek(s->pb, offset, SEEK_SET) < 0)
00572         return -1;
00573 
00574     dv_offset_reset(c, offset / c->sys->frame_size);
00575     return 0;
00576 }
00577 
00578 static int dv_read_close(AVFormatContext *s)
00579 {
00580     RawDVContext *c = s->priv_data;
00581     av_free(c->dv_demux);
00582     return 0;
00583 }
00584 
00585 static int dv_probe(AVProbeData *p)
00586 {
00587     unsigned state, marker_pos = 0;
00588     int i;
00589     int matches = 0;
00590     int secondary_matches = 0;
00591 
00592     if (p->buf_size < 5)
00593         return 0;
00594 
00595     state = AV_RB32(p->buf);
00596     for (i = 4; i < p->buf_size; i++) {
00597         if ((state & 0xffffff7f) == 0x1f07003f)
00598             matches++;
00599         // any section header, also with seq/chan num != 0,
00600         // should appear around every 12000 bytes, at least 10 per frame
00601         if ((state & 0xff07ff7f) == 0x1f07003f)
00602             secondary_matches++;
00603         if (state == 0x003f0700 || state == 0xff3f0700)
00604             marker_pos = i;
00605         if (state == 0xff3f0701 && i - marker_pos == 80)
00606             matches++;
00607         state = (state << 8) | p->buf[i];
00608     }
00609 
00610     if (matches && p->buf_size / matches < 1024*1024) {
00611         if (matches > 4 || (secondary_matches >= 10 && p->buf_size / secondary_matches < 24000))
00612             return AVPROBE_SCORE_MAX*3/4; // not max to avoid dv in mov to match
00613         return AVPROBE_SCORE_MAX/4;
00614     }
00615     return 0;
00616 }
00617 
00618 #if CONFIG_DV_DEMUXER
00619 AVInputFormat ff_dv_demuxer = {
00620     .name           = "dv",
00621     .long_name      = NULL_IF_CONFIG_SMALL("DV video format"),
00622     .priv_data_size = sizeof(RawDVContext),
00623     .read_probe     = dv_probe,
00624     .read_header    = dv_read_header,
00625     .read_packet    = dv_read_packet,
00626     .read_close     = dv_read_close,
00627     .read_seek      = dv_read_seek,
00628     .extensions = "dv,dif",
00629 };
00630 #endif