nihav-codec-support/src/codecs/h263/decoder.rs

   1 //use std::mem;
   2 use nihav_core::codecs::DecoderError;
   3 use nihav_core::frame::*;
   4 use super::super::*;
   5 use super::super::blockdsp;
   6 use super::*;
   7 //use super::code::*;
   8 use nihav_core::formats;
   9
  10 #[allow(dead_code)]
  11 struct MVInfo {
  12     mv:         Vec<MV>,
  13     mb_w:       usize,
  14     mb_stride:  usize,
  15     mb_start:   usize,
  16     top:        bool,
  17     mvmode:     MVMode,
  18 }
  19
  20 impl MVInfo {
  21     fn new() -> Self { MVInfo{ mv: Vec::new(), mb_w: 0, mb_stride: 0, mb_start: 0, top: true, mvmode: MVMode::Old } }
  22     fn reset(&mut self, mb_w: usize, mb_start: usize, mvmode: MVMode) {
  23         self.mb_start  = mb_start;
  24         self.mb_w      = mb_w;
  25         self.mb_stride = mb_w * 2 + 2;
  26         self.mv.resize(self.mb_stride * 3, ZERO_MV);
  27         self.mvmode    = mvmode;
  28     }
  29     fn update_row(&mut self) {
  30         self.mb_start = self.mb_w + 1;
  31         self.top      = false;
  32         for i in 0..self.mb_stride {
  33             self.mv[i] = self.mv[self.mb_stride * 2 + i];
  34         }
  35     }
  36     #[allow(non_snake_case)]
  37     fn predict(&mut self, mb_x: usize, blk_no: usize, use4: bool, diff: MV, first_line: bool, first_mb: bool) -> MV {
  38         let A;
  39         let B;
  40         let C;
  41         let last = mb_x == self.mb_w - 1;
  42         match blk_no {
  43             0 => {
  44                     if mb_x != self.mb_start {
  45                         A = if !first_mb   { self.mv[self.mb_stride + mb_x * 2 - 1] } else { ZERO_MV };
  46                         B = if !first_line { self.mv[                 mb_x * 2] } else { A };
  47                         C = if !first_line && !last { self.mv[mb_x * 2 + 2] } else { ZERO_MV };
  48                     } else {
  49                         A = ZERO_MV; B = ZERO_MV; C = ZERO_MV;
  50                     }
  51                 },
  52             1 => {
  53                     A = self.mv[self.mb_stride + mb_x * 2];
  54                     B = if !first_line { self.mv[mb_x * 2 + 1] } else { A };
  55                     C = if !first_line && !last { self.mv[mb_x * 2 + 2] } else { ZERO_MV/*A*/ };
  56                 },
  57             2 => {
  58                     A = if mb_x != self.mb_start { self.mv[self.mb_stride * 2 + mb_x * 2 - 1] } else { ZERO_MV };
  59                     B = self.mv[self.mb_stride + mb_x * 2];
  60                     C = self.mv[self.mb_stride + mb_x * 2 + 1];
  61                 },
  62             3 => {
  63                     A = self.mv[self.mb_stride * 2 + mb_x * 2];
  64                     B = self.mv[self.mb_stride * 1 + mb_x * 2 + 1];
  65                     C = self.mv[self.mb_stride * 1 + mb_x * 2];
  66                 },
  67             _ => { return ZERO_MV; }
  68         }
  69         let pred_mv = MV::pred(A, B, C);
  70         let new_mv = MV::add_umv(pred_mv, diff, self.mvmode);
  71         if !use4 {
  72             self.mv[self.mb_stride * 1 + mb_x * 2 + 0] = new_mv;
  73             self.mv[self.mb_stride * 1 + mb_x * 2 + 1] = new_mv;
  74             self.mv[self.mb_stride * 2 + mb_x * 2 + 0] = new_mv;
  75             self.mv[self.mb_stride * 2 + mb_x * 2 + 1] = new_mv;
  76         } else {
  77             match blk_no {
  78                 0 => { self.mv[self.mb_stride * 1 + mb_x * 2 + 0] = new_mv; },
  79                 1 => { self.mv[self.mb_stride * 1 + mb_x * 2 + 1] = new_mv; },
  80                 2 => { self.mv[self.mb_stride * 2 + mb_x * 2 + 0] = new_mv; },
  81                 3 => { self.mv[self.mb_stride * 2 + mb_x * 2 + 1] = new_mv; },
  82                 _ => {},
  83             };
  84         }
  85
  86         new_mv
  87     }
  88     fn set_zero_mv(&mut self, mb_x: usize) {
  89         self.mv[self.mb_stride * 1 + mb_x * 2 + 0] = ZERO_MV;
  90         self.mv[self.mb_stride * 1 + mb_x * 2 + 1] = ZERO_MV;
  91         self.mv[self.mb_stride * 2 + mb_x * 2 + 0] = ZERO_MV;
  92         self.mv[self.mb_stride * 2 + mb_x * 2 + 1] = ZERO_MV;
  93     }
  94     fn get_mv(&self, mb_x: usize, blk_no: usize) -> MV {
  95         self.mv[self.mb_stride + mb_x * 2 + (blk_no & 1) + (blk_no >> 1) * self.mb_stride]
  96     }
  97 }
  98
  99 #[allow(dead_code)]
 100 #[derive(Clone,Copy)]
 101 struct BMB {
 102     num_mv: usize,
 103     mv_f:   [MV; 4],
 104     mv_b:   [MV; 4],
 105     fwd:    bool,
 106     blk:    [[i16; 64]; 6],
 107     cbp:    u8,
 108 }
 109
 110 impl BMB {
 111     fn new() -> Self { BMB {blk: [[0; 64]; 6], cbp: 0, fwd: false, mv_f: [ZERO_MV; 4], mv_b: [ZERO_MV; 4], num_mv: 0} }
 112 }
 113
 114 #[derive(Clone,Copy)]
 115 struct PredCoeffs {
 116     hor: [[i16; 8]; 6],
 117     ver: [[i16; 8]; 6],
 118 }
 119
 120 const ZERO_PRED_COEFFS: PredCoeffs = PredCoeffs { hor: [[0; 8]; 6], ver: [[0; 8]; 6] };
 121
 122 pub const H263DEC_OPT_USES_GOB: u32     = 0x0001;
 123 pub const H263DEC_OPT_SLICE_RESET: u32  = 0x0002;
 124 pub const H263DEC_OPT_HAS_B_FRAMES: u32 = 0x0004;
 125
 126 pub struct H263BaseDecoder {
 127     w:          usize,
 128     h:          usize,
 129     mb_w:       usize,
 130     mb_h:       usize,
 131     num_mb:     usize,
 132     ftype:      Type,
 133     ipbs:       IPBShuffler,
 134     next_ts:    u16,
 135     last_ts:    u16,
 136     tsdiff:     u16,
 137     has_b:      bool,
 138     b_data:     Vec<BMB>,
 139     pred_coeffs: Vec<PredCoeffs>,
 140     is_gob:     bool,
 141     slice_reset: bool,
 142     may_have_b_frames: bool,
 143     mv_data:    Vec<BlockMVInfo>,
 144     blk:        [[i16; 64]; 6],
 145 }
 146
 147 #[inline]
 148 fn clip_dc(dc: i16) -> i16 {
 149     if dc <= 0 { 0 }
 150     else if dc > 2046 { 2047 }
 151     else { dc | 1 }
 152 }
 153
 154 #[inline]
 155 fn clip_ac(ac: i16) -> i16 {
 156     if ac < -2048 { -2048 }
 157     else if ac > 2047 { 2047 }
 158     else { ac }
 159 }
 160
 161 #[allow(dead_code)]
 162 impl H263BaseDecoder {
 163     pub fn new_with_opts(options: u32) -> Self {
 164         let is_gob              = (options & H263DEC_OPT_USES_GOB) != 0;
 165         let slice_reset         = (options & H263DEC_OPT_SLICE_RESET) != 0;
 166         let may_have_b_frames   = (options & H263DEC_OPT_HAS_B_FRAMES) != 0;
 167         H263BaseDecoder{
 168             w: 0, h: 0, mb_w: 0, mb_h: 0, num_mb: 0,
 169             ftype: Type::Special,
 170             ipbs: IPBShuffler::new(),
 171             last_ts: 0, next_ts: 0, tsdiff: 0,
 172             has_b: false, b_data: Vec::new(),
 173             pred_coeffs: Vec::new(),
 174             is_gob, slice_reset,
 175             may_have_b_frames,
 176             mv_data: Vec::new(),
 177             blk: [[0; 64]; 6],
 178         }
 179     }
 180     pub fn new(is_gob: bool) -> Self {
 181         Self::new_with_opts(H263DEC_OPT_SLICE_RESET | (if is_gob { H263DEC_OPT_USES_GOB } else { 0 }))
 182     }
 183     pub fn new_b_frames(is_gob: bool) -> Self {
 184         Self::new_with_opts(H263DEC_OPT_SLICE_RESET | H263DEC_OPT_HAS_B_FRAMES | (if is_gob { H263DEC_OPT_USES_GOB } else { 0 }))
 185     }
 186
 187     pub fn is_intra(&self) -> bool { self.ftype == Type::I }
 188     pub fn get_frame_type(&self) -> FrameType {
 189         match self.ftype {
 190             Type::I       => FrameType::I,
 191             Type::P       => FrameType::P,
 192             Type::B       => FrameType::B,
 193             Type::PB      => FrameType::P,
 194             Type::Skip    => FrameType::Skip,
 195             Type::Special => FrameType::Skip,
 196         }
 197     }
 198     pub fn get_dimensions(&self) -> (usize, usize) { (self.w, self.h) }
 199
 200     fn decode_intra_mb(&mut self, bd: &mut BlockDecoder, bdsp: &BlockDSP, mb_pos: usize, binfo: &BlockInfo, sstate: &SliceState, apply_acpred: bool) -> DecoderResult<()> {
 201         for i in 0..6 {
 202             bd.decode_block_intra(&binfo, &sstate, binfo.get_q(), i, (binfo.cbp & (1 << (5 - i))) != 0, &mut self.blk[i])?;
 203             if apply_acpred && (binfo.acpred != ACPredMode::None) {
 204                 let has_b = (i == 1) || (i == 3) || !sstate.first_mb;
 205                 let has_a = (i == 2) || (i == 3) || !sstate.first_line;
 206                 let (b_mb, b_blk) = if has_b {
 207                         if (i == 1) || (i == 3) {
 208                             (mb_pos, i - 1)
 209                         } else if i < 4 {
 210                             (mb_pos - 1, i + 1)
 211                         } else {
 212                             (mb_pos - 1, i)
 213                         }
 214                     } else { (0, 0) };
 215                 let (a_mb, a_blk) = if has_a {
 216                         if (i == 2) || (i == 3) {
 217                             (mb_pos, i - 2)
 218                         } else if i < 4 {
 219                             (mb_pos - self.mb_w, i + 2)
 220                         } else {
 221                             (mb_pos - self.mb_w, i)
 222                         }
 223                     } else { (0, 0) };
 224                 match binfo.acpred {
 225                     ACPredMode::DC   => {
 226                                 let dc;
 227                                 if has_a && has_b {
 228                                     dc = (self.pred_coeffs[b_mb].hor[b_blk][0] + self.pred_coeffs[a_mb].ver[a_blk][0]) / 2;
 229                                 } else if has_a {
 230                                     dc = self.pred_coeffs[a_mb].ver[a_blk][0];
 231                                 } else if has_b {
 232                                     dc = self.pred_coeffs[b_mb].hor[b_blk][0];
 233                                 } else {
 234                                     dc = 1024;
 235                                 }
 236                                 self.blk[i][0] = clip_dc(self.blk[i][0] + dc);
 237                             },
 238                     ACPredMode::Hor  => {
 239                             if has_b {
 240                                 for k in 0..8 {
 241                                     self.blk[i][k * 8] += self.pred_coeffs[b_mb].hor[b_blk][k];
 242                                 }
 243                                 for k in 1..8 {
 244                                     self.blk[i][k * 8] = clip_ac(self.blk[i][k * 8]);
 245                                 }
 246                             } else {
 247                                 self.blk[i][0] += 1024;
 248                             }
 249                             self.blk[i][0] = clip_dc(self.blk[i][0]);
 250                         },
 251                     ACPredMode::Ver  => {
 252                             if has_a {
 253                                 for k in 0..8 {
 254                                     self.blk[i][k] += self.pred_coeffs[a_mb].ver[a_blk][k];
 255                                 }
 256                                 for k in 1..8 {
 257                                     self.blk[i][k] = clip_ac(self.blk[i][k]);
 258                                 }
 259                             } else {
 260                                 self.blk[i][0] += 1024;
 261                             }
 262                             self.blk[i][0] = clip_dc(self.blk[i][0]);
 263                         },
 264                     ACPredMode::None => {},
 265                 };
 266                 for t in 0..8 { self.pred_coeffs[mb_pos].hor[i][t] = self.blk[i][t * 8]; }
 267                 for t in 0..8 { self.pred_coeffs[mb_pos].ver[i][t] = self.blk[i][t]; }
 268             }
 269             bdsp.idct(&mut self.blk[i]);
 270         }
 271         Ok(())
 272     }
 273     fn decode_inter_mb(&mut self, bd: &mut BlockDecoder, bdsp: &BlockDSP, binfo: &BlockInfo, sstate: &SliceState) -> DecoderResult<()> {
 274         for i in 0..6 {
 275             bd.decode_block_inter(&binfo, &sstate, binfo.get_q(), i, ((binfo.cbp >> (5 - i)) & 1) != 0, &mut self.blk[i])?;
 276             bdsp.idct(&mut self.blk[i]);
 277         }
 278         Ok(())
 279     }
 280     pub fn parse_frame(&mut self, bd: &mut BlockDecoder, bdsp: &BlockDSP) -> DecoderResult<NABufferType> {
 281         let pinfo = bd.decode_pichdr()?;
 282         let mut mvi = MVInfo::new();
 283         let mut mvi2 = MVInfo::new();
 284         let mut cbpi = CBPInfo::new();
 285
 286 //todo handle res change
 287         self.w = pinfo.w;
 288         self.h = pinfo.h;
 289         self.mb_w = (pinfo.w + 15) >> 4;
 290         self.mb_h = (pinfo.h + 15) >> 4;
 291         self.num_mb = self.mb_w * self.mb_h;
 292         self.ftype = pinfo.mode;
 293         self.has_b = pinfo.is_pb();
 294
 295         if self.has_b {
 296             self.mv_data.truncate(0);
 297         }
 298
 299         let save_b_data = pinfo.mode.is_ref() && self.may_have_b_frames;
 300         if save_b_data {
 301             self.mv_data.truncate(0);
 302         }
 303         let is_b = pinfo.mode == Type::B;
 304
 305         if is_b && (self.mv_data.len() < self.mb_w * self.mb_h) {
 306             return Err(DecoderError::MissingReference);
 307         }
 308
 309         let tsdiff = if pinfo.is_pb() { pinfo.ts.wrapping_sub(self.last_ts) >> 1 }
 310                      else { self.last_ts.wrapping_sub(self.next_ts) >> 1 };
 311         let bsdiff = if pinfo.is_pb() { (pinfo.get_pbinfo().get_trb() as u16) << 7 }
 312                      else { pinfo.ts.wrapping_sub(self.next_ts) >> 1 };
 313
 314         let fmt = formats::YUV420_FORMAT;
 315         let vinfo = NAVideoInfo::new(self.w, self.h, false, fmt);
 316         let bufinfo = alloc_video_buffer(vinfo, 4)?;
 317         let mut buf = bufinfo.get_vbuf().unwrap();
 318
 319         let mut slice = if self.is_gob {
 320                 SliceInfo::get_default_slice(&pinfo)
 321             } else {
 322                 bd.decode_slice_header(&pinfo)?
 323             };
 324         mvi.reset(self.mb_w, 0, pinfo.get_mvmode());
 325         if is_b || pinfo.is_pb() {
 326             mvi2.reset(self.mb_w, 0, pinfo.get_mvmode());
 327         }
 328         cbpi.reset(self.mb_w);
 329
 330         let mut sstate = SliceState::new(pinfo.mode == Type::I);
 331         let mut mb_pos = 0;
 332         let apply_acpred = (pinfo.mode == Type::I) && pinfo.plusinfo.is_some() && pinfo.plusinfo.unwrap().aic;
 333         if apply_acpred {
 334             self.pred_coeffs.truncate(0);
 335             self.pred_coeffs.resize(self.mb_w * self.mb_h, ZERO_PRED_COEFFS);
 336         }
 337         sstate.quant = slice.quant;
 338         for mb_y in 0..self.mb_h {
 339             for mb_x in 0..self.mb_w {
 340                 self.blk = [[0; 64]; 6];
 341
 342                 if slice.is_at_end(mb_pos) || (slice.needs_check() && mb_pos > 0 && bd.is_slice_end()) {
 343                     slice = bd.decode_slice_header(&pinfo)?;
 344                     if !self.is_gob && self.slice_reset {
 345                         mvi.reset(self.mb_w, mb_x, pinfo.get_mvmode());
 346                         if is_b || pinfo.is_pb() {
 347                             mvi2.reset(self.mb_w, mb_x, pinfo.get_mvmode());
 348                         }
 349                         cbpi.reset(self.mb_w);
 350                         sstate.reset_slice(mb_x, mb_y);
 351                         sstate.quant = slice.quant;
 352                     }
 353                 }
 354
 355                 let binfo = bd.decode_block_header(&pinfo, &slice, &sstate)?;
 356                 let cbp = binfo.get_cbp();
 357                 cbpi.set_cbp(mb_x, cbp);
 358                 cbpi.set_q(mb_x, binfo.get_q());
 359                 sstate.quant = binfo.get_q();
 360                 if binfo.is_intra() {
 361                     if save_b_data {
 362                         self.mv_data.push(BlockMVInfo::Intra);
 363                     }
 364                     self.decode_intra_mb(bd, bdsp, mb_pos, &binfo, &sstate, apply_acpred)?;
 365                     blockdsp::put_blocks(&mut buf, mb_x, mb_y, &self.blk);
 366                     mvi.set_zero_mv(mb_x);
 367                     if is_b {
 368                         mvi2.set_zero_mv(mb_x);
 369                     } else if pinfo.is_pb() {
 370                         mvi2.predict(mb_x, 0, false, binfo.get_mv2(0), sstate.first_line, sstate.first_mb);
 371                     }
 372                 } else if (binfo.mode != Type::B) && !binfo.is_skipped() {
 373                     if binfo.get_num_mvs() == 1 {
 374                         let mv = mvi.predict(mb_x, 0, false, binfo.get_mv(0), sstate.first_line, sstate.first_mb);
 375                         if save_b_data {
 376                             self.mv_data.push(BlockMVInfo::Inter_1MV(mv));
 377                         }
 378                         if let Some(ref srcbuf) = self.ipbs.get_lastref() {
 379                             bdsp.copy_blocks(&mut buf, srcbuf.clone(), mb_x * 16, mb_y * 16, mv);
 380                         }
 381                         if pinfo.is_pb() {
 382                             mvi2.predict(mb_x, 0, false, binfo.get_mv(0), sstate.first_line, sstate.first_mb);
 383                         }
 384                     } else {
 385                         let mut mv: [MV; 4] = [ZERO_MV, ZERO_MV, ZERO_MV, ZERO_MV];
 386                         for blk_no in 0..4 {
 387                             mv[blk_no] = mvi.predict(mb_x, blk_no, true, binfo.get_mv(blk_no), sstate.first_line, sstate.first_mb);
 388                         }
 389                         if let Some(ref srcbuf) = self.ipbs.get_lastref() {
 390                             bdsp.copy_blocks8x8(&mut buf, srcbuf.clone(), mb_x * 16, mb_y * 16, &mv);
 391                         }
 392                         if pinfo.is_pb() {
 393                             for blk_no in 0..4 {
 394                                 mvi2.predict(mb_x, blk_no, true, binfo.get_mv(blk_no), sstate.first_line, sstate.first_mb);
 395                             }
 396                         }
 397                         if save_b_data {
 398                             self.mv_data.push(BlockMVInfo::Inter_4MV(mv));
 399                         }
 400                     }
 401                     self.decode_inter_mb(bd, bdsp, &binfo, &sstate)?;
 402                     blockdsp::add_blocks(&mut buf, mb_x, mb_y, &self.blk);
 403                     if is_b && !pinfo.is_pb() {
 404                         mvi2.set_zero_mv(mb_x);
 405                     }
 406                 } else if binfo.mode != Type::B {
 407                     self.mv_data.push(BlockMVInfo::Inter_1MV(ZERO_MV));
 408                     mvi.set_zero_mv(mb_x);
 409                     if is_b || pinfo.is_pb() {
 410                         mvi2.set_zero_mv(mb_x);
 411                     }
 412                     if let Some(ref srcbuf) = self.ipbs.get_lastref() {
 413                         bdsp.copy_blocks(&mut buf, srcbuf.clone(), mb_x * 16, mb_y * 16, ZERO_MV);
 414                     }
 415                 } else {
 416                     recon_b_mb(&mut buf, &mut self.ipbs, bdsp, &mut mvi, &mut mvi2, mb_pos, self.mb_w, &sstate, &binfo, &self.mv_data, bsdiff, tsdiff);
 417                     if cbp != 0 {
 418                         self.decode_inter_mb(bd, bdsp, &binfo, &sstate)?;
 419                         blockdsp::add_blocks(&mut buf, mb_x, mb_y, &self.blk);
 420                     }
 421                 }
 422                 if pinfo.is_pb() {
 423                     let mut b_mb = BMB::new();
 424                     let cbp = binfo.get_cbp_b();
 425                     let bq = (((pinfo.get_pbinfo().get_dbquant() + 5) as u16) * (binfo.get_q() as u16)) >> 2;
 426                     let bquant;
 427                     if bq < 1 { bquant = 1; }
 428                     else if bq > 31 { bquant = 31; }
 429                     else { bquant = bq as u8; }
 430
 431                     b_mb.cbp = cbp;
 432                     for i in 0..6 {
 433                         bd.decode_block_inter(&binfo, &sstate, bquant, i, (cbp & (1 << (5 - i))) != 0, &mut b_mb.blk[i])?;
 434                         bdsp.idct(&mut b_mb.blk[i]);
 435                     }
 436
 437                     let is_fwd = binfo.is_b_fwd();
 438                     b_mb.fwd = is_fwd;
 439                     if binfo.get_num_mvs() != 4 {
 440                         let ref_mv = mvi2.get_mv(mb_x, 0);
 441                         let b_mv = if binfo.is_intra() { binfo.get_mv2(1) } else { binfo.get_mv2(0) };
 442                         let src_mv = if is_fwd { ZERO_MV } else { ref_mv.scale(bsdiff, tsdiff) };
 443                         let mv_f = MV::add_umv(src_mv, b_mv, pinfo.get_mvmode());
 444                         let mv_b = MV::b_sub(ref_mv, mv_f, b_mv, bsdiff, tsdiff);
 445                         b_mb.mv_f[0] = mv_f;
 446                         b_mb.mv_b[0] = mv_b;
 447                         b_mb.num_mv = 1;
 448                     } else {
 449                         for blk_no in 0..4 {
 450                             let src_mv = if is_fwd { ZERO_MV } else { mvi2.get_mv(mb_x, blk_no).scale(bsdiff, tsdiff) };
 451                             let mv_f = MV::add_umv(src_mv, binfo.get_mv2(0), pinfo.get_mvmode());
 452                             let mv_b = MV::b_sub(mvi2.get_mv(mb_x, blk_no), mv_f, binfo.get_mv2(0), bsdiff, tsdiff);
 453                             b_mb.mv_f[blk_no] = mv_f;
 454                             b_mb.mv_b[blk_no] = mv_b;
 455                         }
 456                         b_mb.num_mv = 4;
 457                     }
 458                     self.b_data.push(b_mb);
 459                 }
 460                 sstate.next_mb();
 461                 mb_pos += 1;
 462             }
 463             if let Some(plusinfo) = pinfo.plusinfo {
 464                 if plusinfo.deblock {
 465                     bdsp.filter_row(&mut buf, mb_y, self.mb_w, &cbpi);
 466                 }
 467             }
 468             mvi.update_row();
 469             if is_b || pinfo.is_pb() {
 470                 mvi2.update_row();
 471             }
 472             cbpi.update_row();
 473             sstate.new_row();
 474         }
 475
 476         if pinfo.mode.is_ref() {
 477             self.ipbs.add_frame(buf);
 478             self.next_ts = self.last_ts;
 479             self.last_ts = pinfo.ts;
 480             self.tsdiff  = tsdiff;
 481         }
 482
 483         Ok(bufinfo)
 484     }
 485     pub fn flush(&mut self) {
 486         self.ipbs.clear();
 487     }
 488
 489     pub fn get_bframe(&mut self, bdsp: &BlockDSP) -> DecoderResult<NABufferType> {
 490         if !self.has_b || self.ipbs.get_lastref().is_none() || self.ipbs.get_nextref().is_none() {
 491             return Err(DecoderError::MissingReference);
 492         }
 493         self.has_b = false;
 494
 495         let fmt = formats::YUV420_FORMAT;
 496         let vinfo = NAVideoInfo::new(self.w, self.h, false, fmt);
 497         let bufinfo = alloc_video_buffer(vinfo, 4)?;
 498         let b_buf = bufinfo.get_vbuf().unwrap();
 499
 500         if let (Some(ref bck_buf), Some(ref fwd_buf)) = (self.ipbs.get_nextref(), self.ipbs.get_lastref()) {
 501             recon_b_frame(b_buf, fwd_buf.clone(), bck_buf.clone(), self.mb_w, self.mb_h, self.b_data.as_slice(), bdsp);
 502         }
 503
 504         self.b_data.truncate(0);
 505         Ok(bufinfo)
 506     }
 507 }
 508
 509 fn recon_b_mb(buf: &mut NAVideoBuffer<u8>, ipbs: &mut IPBShuffler, bdsp: &BlockDSP, mvi: &mut MVInfo, mvi2: &mut MVInfo, mb_pos: usize, mb_w: usize, sstate: &SliceState, binfo: &BlockInfo, mv_data: &[BlockMVInfo], bsdiff: u16, tsdiff: u16) {
 510     let mb_x = mb_pos % mb_w;
 511     let mb_y = mb_pos / mb_w;
 512
 513     let ref_mv_info = mv_data[mb_pos];
 514     let has_fwd = binfo.get_num_mvs() > 0;
 515     let has_bwd = binfo.get_num_mvs2() > 0;
 516
 517     if has_fwd || has_bwd {
 518         let fwd_mv;
 519         if has_fwd {
 520             fwd_mv = mvi.predict(mb_x, 0, false, binfo.get_mv(0), sstate.first_line, sstate.first_mb);
 521         } else {
 522             fwd_mv = ZERO_MV;
 523             mvi.set_zero_mv(mb_x);
 524         }
 525         let bwd_mv;
 526         if has_bwd {
 527             bwd_mv = mvi2.predict(mb_x, 0, false, binfo.get_mv2(0), sstate.first_line, sstate.first_mb);
 528         } else {
 529             bwd_mv = ZERO_MV;
 530             mvi2.set_zero_mv(mb_x);
 531         }
 532         if let (Some(ref fwd_buf), Some(ref bck_buf)) = (ipbs.get_nextref(), ipbs.get_lastref()) {
 533             if has_fwd && has_bwd {
 534                 bdsp.copy_blocks(buf, fwd_buf.clone(), mb_x * 16, mb_y * 16, fwd_mv);
 535                 bdsp.avg_blocks (buf, bck_buf.clone(), mb_x * 16, mb_y * 16, bwd_mv);
 536             } else if has_fwd {
 537                 bdsp.copy_blocks(buf, fwd_buf.clone(), mb_x * 16, mb_y * 16, fwd_mv);
 538             } else {
 539                 bdsp.copy_blocks(buf, bck_buf.clone(), mb_x * 16, mb_y * 16, bwd_mv);
 540             }
 541         }
 542     } else {
 543         if let BlockMVInfo::Inter_4MV(mvs) = ref_mv_info {
 544             let mut mv_f = [ZERO_MV; 4];
 545             let mut mv_b = [ZERO_MV; 4];
 546             for blk_no in 0..4 {
 547                 let ref_mv = mvs[blk_no];
 548                 let ref_mv_fwd = ref_mv.scale(bsdiff, tsdiff);
 549                 let ref_mv_bwd = ref_mv - ref_mv_fwd;
 550                 mv_f[blk_no] = ref_mv_fwd;
 551                 mv_b[blk_no] = ref_mv_bwd;
 552             }
 553             if let (Some(ref fwd_buf), Some(ref bck_buf)) = (ipbs.get_nextref(), ipbs.get_lastref()) {
 554                 bdsp.copy_blocks8x8(buf, fwd_buf.clone(), mb_x * 16, mb_y * 16, &mv_f);
 555                 bdsp.avg_blocks8x8 (buf, bck_buf.clone(), mb_x * 16, mb_y * 16, &mv_b);
 556             }
 557         } else {
 558             let ref_mv = if let BlockMVInfo::Inter_1MV(mv_) = ref_mv_info { mv_ } else { ZERO_MV };
 559             let ref_mv_fwd = ref_mv.scale(bsdiff, tsdiff);
 560             let ref_mv_bwd = MV::b_sub(ref_mv, ref_mv_fwd, ZERO_MV, bsdiff, tsdiff);
 561
 562             if let (Some(ref fwd_buf), Some(ref bck_buf)) = (ipbs.get_nextref(), ipbs.get_lastref()) {
 563                 bdsp.copy_blocks(buf, fwd_buf.clone(), mb_x * 16, mb_y * 16, ref_mv_fwd);
 564                 bdsp.avg_blocks (buf, bck_buf.clone(), mb_x * 16, mb_y * 16, ref_mv_bwd);
 565             }
 566         }
 567         mvi.set_zero_mv(mb_x);
 568         mvi2.set_zero_mv(mb_x);
 569     }
 570 }
 571
 572 fn recon_b_frame(mut b_buf: NAVideoBufferRef<u8>, bck_buf: NAVideoBufferRef<u8>, fwd_buf: NAVideoBufferRef<u8>,
 573                  mb_w: usize, mb_h: usize, b_data: &[BMB], bdsp: &BlockDSP) {
 574     let mut cbpi = CBPInfo::new();
 575     let mut cur_mb = 0;
 576     cbpi.reset(mb_w);
 577     for mb_y in 0..mb_h {
 578         for mb_x in 0..mb_w {
 579             let num_mv = b_data[cur_mb].num_mv;
 580             let is_fwd = b_data[cur_mb].fwd;
 581             let cbp    = b_data[cur_mb].cbp;
 582             cbpi.set_cbp(mb_x, cbp);
 583             if num_mv == 1 {
 584                 bdsp.copy_blocks(&mut b_buf, fwd_buf.clone(), mb_x * 16, mb_y * 16, b_data[cur_mb].mv_b[0]);
 585                 if !is_fwd {
 586                     bdsp.avg_blocks(&mut b_buf, bck_buf.clone(), mb_x * 16, mb_y * 16, b_data[cur_mb].mv_f[0]);
 587                 }
 588             } else {
 589                 bdsp.copy_blocks8x8(&mut b_buf, fwd_buf.clone(), mb_x * 16, mb_y * 16, &b_data[cur_mb].mv_b);
 590                 if !is_fwd {
 591                     bdsp.avg_blocks8x8(&mut b_buf, bck_buf.clone(), mb_x * 16, mb_y * 16, &b_data[cur_mb].mv_f);
 592                 }
 593             }
 594             if cbp != 0 {
 595                 blockdsp::add_blocks(&mut b_buf, mb_x, mb_y, &b_data[cur_mb].blk);
 596             }
 597             cur_mb += 1;
 598         }
 599         cbpi.update_row();
 600     }
 601 }