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All: preliminary support for audio while playing faster/slower (1/4 -> 4).
[vlc] / modules / packetizer / vc1.c
1 /*****************************************************************************
2  * vc1.c
3  *****************************************************************************
4  * Copyright (C) 2001, 2002, 2006 the VideoLAN team
5  * $Id: copy.c 18231 2006-12-03 17:02:02Z courmisch $
6  *
7  * Authors: Laurent Aimar <fenrir@via.ecp.fr>
8  *          Gildas Bazin <gbazin@videolan.org>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License as published by
12  * the Free Software Foundation; either version 2 of the License, or
13  * (at your option) any later version.
14  *
15  * This program is distributed in the hope that it will be useful,
16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
18  * GNU General Public License for more details.
19  *
20  * You should have received a copy of the GNU General Public License
21  * along with this program; if not, write to the Free Software
22  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
23  *****************************************************************************/
24
25 /*****************************************************************************
26  * Preamble
27  *****************************************************************************/
28 #include <stdlib.h>                                      /* malloc(), free() */
29
30 #include <vlc/vlc.h>
31 #include <vlc_codec.h>
32 #include <vlc_block.h>
33
34 #include "vlc_bits.h"
35 #include "vlc_block_helper.h"
36
37 /*****************************************************************************
38  * Module descriptor
39  *****************************************************************************/
40 static int  Open ( vlc_object_t * );
41 static void Close( vlc_object_t * );
42
43 vlc_module_begin();
44     set_category( CAT_SOUT );
45     set_subcategory( SUBCAT_SOUT_PACKETIZER );
46     set_description( _("VC-1 packetizer") );
47     set_capability( "packetizer", 50 );
48     set_callbacks( Open, Close );
49 vlc_module_end();
50
51 /*****************************************************************************
52  * Local prototypes
53  *****************************************************************************/
54 struct decoder_sys_t
55 {
56     /*
57      * Input properties
58      */
59     block_bytestream_t bytestream;
60     int i_state;
61     int i_offset;
62     uint8_t p_startcode[3];
63
64     /* Current sequence header */
65     vlc_bool_t b_sequence_header;
66     struct
67     {
68         block_t *p_sh;
69         vlc_bool_t b_advanced_profile;
70         vlc_bool_t b_interlaced;
71         vlc_bool_t b_frame_interpolation;
72         vlc_bool_t b_range_reduction;
73         vlc_bool_t b_has_bframe;
74     } sh;
75     vlc_bool_t b_entry_point;
76     struct
77     {
78         block_t *p_ep;
79     } ep;
80
81     /* */
82     vlc_bool_t  b_frame;
83
84     /* Current frame being built */
85     block_t    *p_frame;
86     block_t    **pp_last;
87
88
89     mtime_t i_interpolated_dts;
90 };
91
92 enum
93 {
94     STATE_NOSYNC,
95     STATE_NEXT_SYNC
96 };
97
98 typedef enum
99 {
100     IDU_TYPE_SEQUENCE_HEADER = 0x0f,
101     IDU_TYPE_ENTRY_POINT = 0x0e,
102     IDU_TYPE_FRAME = 0x0D,
103     IDU_TYPE_FIELD = 0x0C,
104     IDU_TYPE_SLICE = 0x0B,
105     IDU_TYPE_END_OF_SEQUENCE = 0x0B,
106
107     IDU_TYPE_SEQUENCE_LEVEL_USER_DATA = 0x1F,
108     IDU_TYPE_ENTRY_POINT_USER_DATA = 0x1E,
109     IDU_TYPE_FRAME_USER_DATA = 0x1D,
110     IDU_TYPE_FIELD_USER_DATA = 0x1C,
111     IDU_TYPE_SLICE_USER_DATA = 0x1B,
112 } idu_type_t;
113
114 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block );
115
116 /*****************************************************************************
117  * Open: probe the packetizer and return score
118  *****************************************************************************
119  * Tries to launch a decoder and return score so that the interface is able
120  * to choose.
121  *****************************************************************************/
122 static int Open( vlc_object_t *p_this )
123 {
124     decoder_t     *p_dec = (decoder_t*)p_this;
125     decoder_sys_t *p_sys;
126
127     if( p_dec->fmt_in.i_codec !=  VLC_FOURCC( 'W', 'V', 'C', '1' ) )
128         return VLC_EGENERIC;
129
130     p_dec->pf_packetize = Packetize;
131
132     /* Create the output format */
133     es_format_Copy( &p_dec->fmt_out, &p_dec->fmt_in );
134     p_dec->p_sys = p_sys = malloc( sizeof( decoder_sys_t ) );
135
136     p_sys->i_state = STATE_NOSYNC;
137     p_sys->bytestream = block_BytestreamInit( p_dec );
138     p_sys->p_startcode[0] = 0x00;
139     p_sys->p_startcode[1] = 0x00;
140     p_sys->p_startcode[2] = 0x01;
141     p_sys->i_offset = 0;
142
143     p_sys->b_sequence_header = VLC_FALSE;
144     p_sys->sh.p_sh = NULL;
145     p_sys->b_entry_point = VLC_FALSE;
146     p_sys->ep.p_ep = NULL;
147
148     p_sys->b_frame = VLC_FALSE;
149     p_sys->p_frame = NULL;
150     p_sys->pp_last = &p_sys->p_frame;
151
152     p_sys->i_interpolated_dts = -1;
153
154
155     if( p_dec->fmt_in.i_extra > 0 )
156     {
157         block_t *p_init = block_New( p_dec, p_dec->fmt_in.i_extra );
158         block_t *p_pic;
159
160         memcpy( p_init->p_buffer, p_dec->fmt_in.p_extra,
161                 p_dec->fmt_in.i_extra );
162
163         while( ( p_pic = Packetize( p_dec, &p_init ) ) )
164             block_Release( p_pic ); /* Should not happen (only sequence header) */
165     }
166
167     return VLC_SUCCESS;
168 }
169
170 /*****************************************************************************
171  * Close:
172  *****************************************************************************/
173 static void Close( vlc_object_t *p_this )
174 {
175     decoder_t     *p_dec = (decoder_t*)p_this;
176     decoder_sys_t *p_sys = p_dec->p_sys;
177
178     block_BytestreamRelease( &p_sys->bytestream );
179     if( p_sys->p_frame )
180         block_Release( p_sys->p_frame );
181     free( p_sys );
182 }
183
184 /*****************************************************************************
185  * Packetize: packetize an access unit
186  *****************************************************************************/
187 static block_t *ParseIDU( decoder_t *p_dec, block_t *p_frag );
188
189 static block_t *Packetize( decoder_t *p_dec, block_t **pp_block )
190 {
191     decoder_sys_t *p_sys = p_dec->p_sys;
192     block_t       *p_pic;
193
194     if( pp_block == NULL || *pp_block == NULL )
195         return NULL;
196
197     if( (*pp_block)->i_flags&(BLOCK_FLAG_DISCONTINUITY|BLOCK_FLAG_CORRUPTED) )
198     {
199         if( (*pp_block)->i_flags&BLOCK_FLAG_CORRUPTED )
200         {
201             p_sys->i_state = STATE_NOSYNC;
202             block_BytestreamFlush( &p_sys->bytestream );
203
204             if( p_sys->p_frame )
205                 block_ChainRelease( p_sys->p_frame );
206             p_sys->p_frame = NULL;
207             p_sys->pp_last = &p_sys->p_frame;
208             p_sys->b_frame = VLC_FALSE;
209         }
210 //        p_sys->i_interpolated_dts = 0;
211         block_Release( *pp_block );
212         return NULL;
213     }
214
215     block_BytestreamPush( &p_sys->bytestream, *pp_block );
216
217     for( ;; )
218     {
219         switch( p_sys->i_state )
220         {
221
222         case STATE_NOSYNC:
223             if( block_FindStartcodeFromOffset( &p_sys->bytestream, &p_sys->i_offset, p_sys->p_startcode, 3 ) == VLC_SUCCESS )
224                 p_sys->i_state = STATE_NEXT_SYNC;
225
226             if( p_sys->i_offset )
227             {
228                 block_SkipBytes( &p_sys->bytestream, p_sys->i_offset );
229                 p_sys->i_offset = 0;
230                 block_BytestreamFlush( &p_sys->bytestream );
231             }
232
233             if( p_sys->i_state != STATE_NEXT_SYNC )
234                 return NULL; /* Need more data */
235
236             p_sys->i_offset = 4; /* To find next startcode */
237
238         case STATE_NEXT_SYNC:
239             /* TODO: If p_block == NULL, flush the buffer without checking the
240              * next sync word */
241
242             /* Find the next startcode */
243             if( block_FindStartcodeFromOffset( &p_sys->bytestream, &p_sys->i_offset, p_sys->p_startcode, 3 ) != VLC_SUCCESS )
244                 return NULL; /* Need more data */
245
246             /* Get the new fragment and set the pts/dts */
247             p_pic = block_New( p_dec, p_sys->i_offset );
248             block_BytestreamFlush( &p_sys->bytestream );
249             p_pic->i_pts = p_sys->bytestream.p_block->i_pts;
250             p_pic->i_dts = p_sys->bytestream.p_block->i_dts;
251             p_pic->i_rate = p_sys->bytestream.p_block->i_rate;
252
253             block_GetBytes( &p_sys->bytestream, p_pic->p_buffer, p_pic->i_buffer );
254
255             p_sys->i_offset = 0;
256
257             /* Parse and return complete frame */
258             p_pic = ParseIDU( p_dec, p_pic );
259
260             /* Don't reuse the same timestamps several times */
261             if( p_sys->p_frame &&
262                 p_sys->p_frame->i_dts == p_sys->bytestream.p_block->i_dts &&
263                 p_sys->p_frame->i_pts == p_sys->bytestream.p_block->i_pts )
264             {
265                 p_sys->bytestream.p_block->i_pts = -1;
266                 p_sys->bytestream.p_block->i_dts = -1;
267             }
268
269             /* */
270             if( !p_pic )
271             {
272                 p_sys->i_state = STATE_NOSYNC;
273                 break;
274             }
275             /* */
276             if( p_sys->i_interpolated_dts < 0 )
277             {
278                 msg_Dbg( p_dec, "need a starting pts/dts" );
279                 p_sys->i_state = STATE_NOSYNC;
280                 block_Release( p_pic );
281                 break;
282             }
283
284             /* So p_block doesn't get re-added several times */
285             *pp_block = block_BytestreamPop( &p_sys->bytestream );
286
287             p_sys->i_state = STATE_NOSYNC;
288
289             return p_pic;
290         }
291     }
292 }
293
294 /* DecodeRIDU: decode the startcode emulation prevention (same than h264) */
295 static void DecodeRIDU( uint8_t *p_ret, int *pi_ret, uint8_t *src, int i_src )
296 {
297     uint8_t *end = &src[i_src];
298     uint8_t *dst_end = &p_ret[*pi_ret];
299     uint8_t *dst = p_ret;
300
301     while( src < end && dst < dst_end )
302     {
303         if( src < end - 3 && src[0] == 0x00 && src[1] == 0x00 &&
304             src[2] == 0x03 )
305         {
306             *dst++ = 0x00;
307             *dst++ = 0x00;
308
309             src += 3;
310             continue;
311         }
312         *dst++ = *src++;
313     }
314
315     *pi_ret = dst - p_ret;
316 }
317 /* BuildExtraData: gather sequence header and entry point */
318 static void BuildExtraData( decoder_t *p_dec )
319 {
320     decoder_sys_t *p_sys = p_dec->p_sys;
321     es_format_t *p_es = &p_dec->fmt_out;
322     int i_extra;
323     if( !p_sys->b_sequence_header || !p_sys->b_entry_point )
324         return;
325
326     i_extra = p_sys->sh.p_sh->i_buffer + p_sys->ep.p_ep->i_buffer;
327     if( p_es->i_extra != i_extra )
328     {
329         p_es->i_extra = i_extra;
330         p_es->p_extra = realloc( p_dec->fmt_out.p_extra, p_es->i_extra );
331     }
332     memcpy( p_es->p_extra,
333             p_sys->sh.p_sh->p_buffer, p_sys->sh.p_sh->i_buffer );
334     memcpy( (uint8_t*)p_es->p_extra + p_sys->sh.p_sh->i_buffer,
335             p_sys->ep.p_ep->p_buffer, p_sys->ep.p_ep->i_buffer );
336 }
337 /* ParseIDU: parse an Independant Decoding Unit */
338 static block_t *ParseIDU( decoder_t *p_dec, block_t *p_frag )
339 {
340     decoder_sys_t *p_sys = p_dec->p_sys;
341     block_t *p_pic;
342     const idu_type_t idu = p_frag->p_buffer[3];
343
344     if( !p_sys->b_sequence_header && idu != IDU_TYPE_SEQUENCE_HEADER )
345     {
346         msg_Warn( p_dec, "waiting for sequence header" );
347         block_Release( p_frag );
348         return NULL;
349     }
350     if( p_sys->b_sequence_header && !p_sys->b_entry_point && idu != IDU_TYPE_ENTRY_POINT )
351     {
352         msg_Warn( p_dec, "waiting for entry point" );
353         block_Release( p_frag );
354         return NULL;
355     }
356     /* TODO we do not gather ENTRY_POINT and SEQUENCE_DATA user data
357      * But It should not be a problem for decoder */
358
359     /* Do we have completed a frame */
360     p_pic = NULL;
361     if( p_sys->b_frame &&
362         idu != IDU_TYPE_FRAME_USER_DATA &&
363         idu != IDU_TYPE_FIELD && idu != IDU_TYPE_FIELD_USER_DATA &&
364         idu != IDU_TYPE_SLICE && idu != IDU_TYPE_SLICE_USER_DATA &&
365         idu != IDU_TYPE_END_OF_SEQUENCE )
366     {
367         /* */
368         p_pic = block_ChainGather( p_sys->p_frame );
369
370         /* We can interpolate dts/pts only if we have a frame rate */
371         if( p_dec->fmt_out.video.i_frame_rate != 0 && p_dec->fmt_out.video.i_frame_rate_base != 0 )
372         {
373             //msg_Dbg( p_dec, "-------------- XXX0 dts="I64Fd" pts="I64Fd" interpolated="I64Fd, p_pic->i_dts, p_pic->i_pts, p_sys->i_interpolated_dts );
374             if( p_pic->i_dts <= 0 )
375                 p_pic->i_dts = p_sys->i_interpolated_dts;
376
377             p_sys->i_interpolated_dts += I64C(1000000) * p_dec->fmt_out.video.i_frame_rate_base / p_dec->fmt_out.video.i_frame_rate;
378             if( p_pic->i_pts <= 0 )
379             {
380                 if( !p_sys->sh.b_has_bframe || (p_pic->i_flags & BLOCK_FLAG_TYPE_B ) )
381                     p_pic->i_pts = p_pic->i_dts;
382                 /* TODO compute pts for other case */
383             }
384         }
385         p_sys->i_interpolated_dts = p_pic->i_dts;
386
387         //msg_Dbg( p_dec, "-------------- dts="I64Fd" pts="I64Fd, p_pic->i_dts, p_pic->i_pts );
388
389         /* Reset context */
390         p_sys->p_frame = NULL;
391         p_sys->pp_last = &p_sys->p_frame;
392     }
393
394     /*  */
395     if( p_sys->p_frame )
396     {
397         block_t *p_frame = p_sys->p_frame;
398         if( p_frame->i_dts < 0 )
399             p_frame->i_dts = p_frag->i_dts;
400         if( p_frame->i_pts < 0 )
401             p_frame->i_pts = p_frag->i_pts;
402     }
403     block_ChainLastAppend( &p_sys->pp_last, p_frag );
404
405     /* Parse IDU */
406     if( idu == IDU_TYPE_SEQUENCE_HEADER )
407     {
408         es_format_t *p_es = &p_dec->fmt_out;
409         bs_t s;
410         int i_profile;
411         uint8_t ridu[32];
412         int     i_ridu = sizeof(ridu);
413
414         /* */
415         if( p_sys->sh.p_sh )
416             block_Release( p_sys->sh.p_sh );
417         p_sys->sh.p_sh = block_Duplicate( p_frag );
418
419         /* Extract the raw IDU */
420         DecodeRIDU( ridu, &i_ridu, &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
421
422         /* Auto detect VC-1_SPMP_PESpacket_PayloadFormatHeader (SMPTE RP 227) for simple/main profile
423          * TODO find a test case and valid it */
424         if( i_ridu > 4 && (ridu[0]&0x80) == 0 ) /* for advanced profile, the first bit is 1 */
425         {
426             video_format_t *p_v = &p_dec->fmt_in.video;
427             const int i_potential_width  = GetWBE( &ridu[0] );
428             const int i_potential_height = GetWBE( &ridu[2] );
429
430             if( i_potential_width >= 2  && i_potential_width <= 8192 &&
431                 i_potential_height >= 2 && i_potential_height <= 8192 )
432             {
433                 if( ( p_v->i_width <= 0 && p_v->i_height <= 0  ) ||
434                     ( p_v->i_width  == i_potential_width &&  p_v->i_height == i_potential_height ) )
435                 {
436                     static const uint8_t startcode[4] = { 0x00, 0x00, 0x01, IDU_TYPE_SEQUENCE_HEADER };
437                     p_es->video.i_width  = i_potential_width;
438                     p_es->video.i_height = i_potential_height;
439
440                     /* Remove it */
441                     p_frag->p_buffer += 4;
442                     p_frag->i_buffer -= 4;
443                     memcpy( p_frag->p_buffer, startcode, sizeof(startcode) );
444                 }
445             }
446         }
447
448         /* Parse it */
449         bs_init( &s, ridu, i_ridu );
450         i_profile = bs_read( &s, 2 );
451         if( i_profile == 3 )
452         {
453             const int i_level = bs_read( &s, 3 );
454
455             /* Advanced profile */
456             p_sys->sh.b_advanced_profile = VLC_TRUE;
457             p_sys->sh.b_range_reduction = VLC_FALSE;
458             p_sys->sh.b_has_bframe = VLC_TRUE;
459
460             bs_skip( &s, 2+3+5+1 ); // chroma format + frame rate Q + bit rate Q + postprocflag
461
462             p_es->video.i_width  = 2*bs_read( &s, 12 )+2;
463             p_es->video.i_height = 2*bs_read( &s, 12 )+2;
464
465             if( !p_sys->b_sequence_header )
466                 msg_Dbg( p_dec, "found sequence header for advanced profile level L%d resolution %dx%d",
467                          i_level, p_es->video.i_width, p_es->video.i_height);
468
469             bs_skip( &s, 1 );// pulldown
470             p_sys->sh.b_interlaced = bs_read( &s, 1 );
471             bs_skip( &s, 1 );// frame counter
472             p_sys->sh.b_frame_interpolation = bs_read( &s, 1 );
473             bs_skip( &s, 1 );       // Reserved
474             bs_skip( &s, 1 );       // Psf
475
476             if( bs_read( &s, 1 ) )  /* Display extension */
477             {
478                 const int i_display_width  = bs_read( &s, 14 )+1;
479                 const int i_display_height = bs_read( &s, 14 )+1;
480
481                 p_es->video.i_aspect = VOUT_ASPECT_FACTOR * i_display_width / i_display_height;
482
483                 if( !p_sys->b_sequence_header )
484                     msg_Dbg( p_dec, "display size %dx%d", i_display_width, i_display_height );
485
486                 if( bs_read( &s, 1 ) )  /* Pixel aspect ratio (PAR/SAR) */
487                 {
488                     static const int p_ar[16][2] = {
489                         { 0, 0}, { 1, 1}, {12,11}, {10,11}, {16,11}, {40,33},
490                         {24,11}, {20,11}, {32,11}, {80,33}, {18,11}, {15,11},
491                         {64,33}, {160,99},{ 0, 0}, { 0, 0}
492                     };
493                     int i_ar = bs_read( &s, 4 );
494                     int i_ar_w, i_ar_h;
495
496                     if( i_ar == 15 )
497                     {
498                         i_ar_w = bs_read( &s, 8 );
499                         i_ar_h = bs_read( &s, 8 );
500                     }
501                     else
502                     {
503                         i_ar_w = p_ar[i_ar][0];
504                         i_ar_h = p_ar[i_ar][1];
505                     }
506                     vlc_ureduce( &i_ar_w, &i_ar_h, i_ar_w, i_ar_h, 0 );
507                     if( !p_sys->b_sequence_header )
508                         msg_Dbg( p_dec, "aspect ratio %d:%d", i_ar_w, i_ar_h );
509                 }
510             }
511             if( bs_read( &s, 1 ) )  /* Frame rate */
512             {
513                 int i_fps_num = 0;
514                 int i_fps_den = 0;
515                 if( bs_read( &s, 1 ) )
516                 {
517                     i_fps_num = bs_read( &s, 16 )+1;
518                     i_fps_den = 32;
519                 }
520                 else
521                 {
522                     const int i_nr = bs_read( &s, 8 );
523                     const int i_dn = bs_read( &s, 4 );
524
525                     switch( i_nr )
526                     {
527                     case 1: i_fps_num = 24000; break;
528                     case 2: i_fps_num = 25000; break;
529                     case 3: i_fps_num = 30000; break;
530                     case 4: i_fps_num = 50000; break;
531                     case 5: i_fps_num = 60000; break;
532                     case 6: i_fps_num = 48000; break;
533                     case 7: i_fps_num = 72000; break;
534                     }
535                     switch( i_dn )
536                     {
537                     case 1: i_fps_den = 1000; break;
538                     case 2: i_fps_den = 1001; break;
539                     }
540                 }
541                 if( i_fps_num != 0 && i_fps_den != 0 )
542                     vlc_ureduce( &p_es->video.i_frame_rate, &p_es->video.i_frame_rate_base, i_fps_num, i_fps_den, 0 );
543
544                 if( !p_sys->b_sequence_header )
545                     msg_Dbg( p_dec, "frame rate %d/%d", p_es->video.i_frame_rate, p_es->video.i_frame_rate_base );
546             }
547         }
548         else
549         {
550             /* Simple and main profile */
551             p_sys->sh.b_advanced_profile = VLC_FALSE;
552             p_sys->sh.b_interlaced = VLC_FALSE;
553
554             if( !p_sys->b_sequence_header )
555                 msg_Dbg( p_dec, "found sequence header for %s profile", i_profile == 0 ? "simple" : "main" );
556
557             bs_skip( &s, 2+3+5+1+1+     // reserved + frame rate Q + bit rate Q + loop filter + reserved
558                          1+1+1+1+2+     // multiresolution + reserved + fast uv mc + extended mv + dquant
559                          1+1+1+1 );     // variable size transform + reserved + overlap + sync marker
560             p_sys->sh.b_range_reduction = bs_read( &s, 1 );
561             if( bs_read( &s, 3 ) > 0 )
562                 p_sys->sh.b_has_bframe = VLC_TRUE;
563             else
564                 p_sys->sh.b_has_bframe = VLC_FALSE;
565             bs_skip( &s, 2 );           // quantizer
566
567             p_sys->sh.b_frame_interpolation = bs_read( &s, 1 );
568         }
569         p_sys->b_sequence_header = VLC_TRUE;
570         BuildExtraData( p_dec );
571     }
572     else if( idu == IDU_TYPE_ENTRY_POINT )
573     {
574         if( p_sys->ep.p_ep )
575             block_Release( p_sys->ep.p_ep );
576         p_sys->ep.p_ep = block_Duplicate( p_frag );
577
578         p_sys->b_entry_point = VLC_TRUE;
579         BuildExtraData( p_dec );
580     }
581     else if( idu == IDU_TYPE_FRAME )
582     {
583         bs_t s;
584         uint8_t ridu[8];
585         int     i_ridu = sizeof(ridu);
586
587         /* Extract the raw IDU */
588         DecodeRIDU( ridu, &i_ridu, &p_frag->p_buffer[4], p_frag->i_buffer - 4 );
589
590         /* Parse it + interpolate pts/dts if possible */
591         bs_init( &s, ridu, i_ridu );
592
593         if( p_sys->sh.b_advanced_profile )
594         {
595             int i_fcm = 0;
596
597             if( p_sys->sh.b_interlaced )
598             {
599                 if( bs_read( &s, 1 ) )
600                 {
601                     if( bs_read( &s, 1 ) )
602                         i_fcm = 1;  /* interlaced field */
603                     else
604                         i_fcm = 2;  /* interlaced frame */
605                 }
606             }
607
608             if( i_fcm == 1 ) /*interlaced field */
609             {
610                 /* XXX for mixed I/P we should check reference usage before marking them I (too much work) */
611                 switch( bs_read( &s, 3 ) )
612                 {
613                 case 0: /* II */
614                 case 1: /* IP */
615                 case 2: /* PI */
616                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_I;
617                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_I;
618                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_I;
619                     break;
620                 case 3: /* PP */
621                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_P;
622                     break;
623                 case 4: /* BB */
624                 case 5: /* BBi */
625                 case 6: /* BiB */
626                 case 7: /* BiBi */
627                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_B;
628                     break;
629                 }
630             }
631             else
632             {
633                 if( !bs_read( &s, 1 ) )
634                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_P;
635                 else if( !bs_read( &s, 1 ) )
636                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_B;
637                 else if( !bs_read( &s, 1 ) )
638                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_I;
639                 else if( !bs_read( &s, 1 ) )
640                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_B;   /* Bi */
641                 else
642                     p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_P;   /* P Skip */
643             }
644         }
645         else
646         {
647             if( p_sys->sh.b_frame_interpolation )
648                 bs_skip( &s, 1 );   // interpolate
649             bs_skip( &s, 2 );       // frame count
650             if( p_sys->sh.b_range_reduction )
651                 bs_skip( &s, 1 );   // range reduction
652
653             if( bs_read( &s, 1 ) )
654                 p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_P;
655             else if( !p_sys->sh.b_has_bframe || bs_read( &s, 1 ) )
656                 p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_I;
657             else
658                 p_sys->p_frame->i_flags |= BLOCK_FLAG_TYPE_B;
659         }
660         p_sys->b_frame = VLC_TRUE;
661     }
662     return p_pic;
663 }
664