[FFmpeg-devel] [PATCH] PB-frames support for i263

[Kostya]

$subj

For now it decodes only P part of PB frames and skips B blocks part
(excellent idea to store data for two frames in one).

Samples are at http://samples.mplayerhq.hu/A-codecs/IMC/
-------------- next part --------------
Index: libavcodec/h263.c
===================================================================
--- libavcodec/h263.c	(revision 16921)
+++ libavcodec/h263.c	(working copy)
@@ -3892,6 +3892,8 @@
     int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
     int16_t *mot_val;
     const int xy= s->mb_x + s->mb_y * s->mb_stride;
+    int cbpb = 0, mvdb = 0;
+    DECLARE_ALIGNED(16, DCTELEM, dblock[64]);
 
     assert(!s->h263_pred);
 
@@ -3924,6 +3926,23 @@
         s->mb_intra = ((cbpc & 4) != 0);
         if (s->mb_intra) goto intra;
 
+        if(s->pb_frame){
+            if(s->impr_pb_frame){
+                if(get_bits1(&s->gb)){
+                    cbpb = get_bits1(&s->gb);
+                    if(cbpb)
+                        mvdb = !get_bits1(&s->gb);
+                    else
+                        mvdb = 1;
+                }
+            }else{
+                mvdb = get_bits1(&s->gb);
+                if(mvdb)
+                    cbpb = get_bits1(&s->gb);
+            }
+            if(cbpb)
+                cbpb = get_bits(&s->gb, 6);
+        }
         cbpy = get_vlc2(&s->gb, cbpy_vlc.table, CBPY_VLC_BITS, 1);
 
         if(s->alt_inter_vlc==0 || (cbpc & 3)!=3)
@@ -3987,12 +4006,25 @@
             }
         }
 
+        if(mvdb){
+            h263_decode_motion(s, 0, 1);
+            h263_decode_motion(s, 0, 1);
+        }
+
         /* decode each block */
         for (i = 0; i < 6; i++) {
             if (h263_decode_block(s, block[i], i, cbp&32) < 0)
                 return -1;
             cbp+=cbp;
         }
+        if(s->pb_frame){
+            cbp = cbpb;
+            for (i = 0; i < 6; i++) {
+                if (h263_decode_block(s, dblock, i, cbp&32) < 0)
+                    return -1;
+                cbp+=cbp;
+            }        
+        }
 
         if(s->obmc){
             if(s->pict_type == FF_P_TYPE && s->mb_x+1<s->mb_width && s->mb_num_left != 1)
@@ -4118,6 +4150,23 @@
         }else
             s->ac_pred = 0;
 
+        if(s->pb_frame){
+            if(s->impr_pb_frame){
+                if(get_bits1(&s->gb)){
+                    cbpb = get_bits1(&s->gb);
+                    if(cbpb)
+                        mvdb = !get_bits1(&s->gb);
+                    else
+                        mvdb = 1;
+                }
+            }else{
+                mvdb = get_bits1(&s->gb);
+                if(mvdb)
+                    cbpb = get_bits1(&s->gb);
+            }
+            if(cbpb)
+                cbpb = get_bits(&s->gb, 6);
+        }
         cbpy = get_vlc2(&s->gb, cbpy_vlc.table, CBPY_VLC_BITS, 1);
         if(cbpy<0){
             av_log(s->avctx, AV_LOG_ERROR, "I cbpy damaged at %d %d\n", s->mb_x, s->mb_y);
@@ -4128,12 +4177,31 @@
             h263_decode_dquant(s);
         }
 
+        if(s->pb_frame){
+            h263_decode_motion(s, 0, 1);
+            h263_decode_motion(s, 0, 1);
+        }
+        if(mvdb){
+            h263_decode_motion(s, 0, 1);
+            h263_decode_motion(s, 0, 1);
+        }
+
         /* decode each block */
         for (i = 0; i < 6; i++) {
             if (h263_decode_block(s, block[i], i, cbp&32) < 0)
                 return -1;
             cbp+=cbp;
         }
+        if(s->pb_frame){
+            cbp = cbpb;
+            s->mb_intra = 0;
+            for (i = 0; i < 6; i++) {
+                if (h263_decode_block(s, dblock, i, cbp&32) < 0)
+                    return -1;
+                cbp+=cbp;
+            }
+            s->mb_intra = 1;
+        }
     }
 end:
 
@@ -6149,6 +6217,8 @@
 {
     int format;
 
+    if(s->gb.buffer_end - s->gb.buffer == 8)
+        return -1;
     /* picture header */
     if (get_bits_long(&s->gb, 22) != 0x20) {
         av_log(s->avctx, AV_LOG_ERROR, "Bad picture start code\n");
@@ -6185,17 +6255,34 @@
         return -1;      /* SAC: off */
     }
     s->obmc= get_bits1(&s->gb);
-    if (get_bits1(&s->gb) != 0) {
-        av_log(s->avctx, AV_LOG_ERROR, "PB frame mode no supported\n");
-        return -1;      /* PB frame mode */
+    s->pb_frame = get_bits1(&s->gb);
+    s->impr_pb_frame = 0;
+
+    if(format == 7){
+        format = get_bits(&s->gb, 3);
+        if(format == 0 || format == 7){
+            av_log(s->avctx, AV_LOG_ERROR, "Wrong Intel H263 format\n");
+            return -1;        
+        }
+        skip_bits(&s->gb, 2);
+        s->loop_filter = get_bits1(&s->gb);
+        skip_bits(&s->gb, 1);
+        s->impr_pb_frame = get_bits1(&s->gb);
+        skip_bits(&s->gb, 10);
+    }else{
+        s->loop_filter = 0;
     }
+    if(format == 6)
+        skip_bits(&s->gb, 23);
 
-    /* skip unknown header garbage */
-    skip_bits(&s->gb, 41);
-
     s->chroma_qscale= s->qscale = get_bits(&s->gb, 5);
     skip_bits1(&s->gb); /* Continuous Presence Multipoint mode: off */
 
+    if(s->pb_frame){
+        skip_bits(&s->gb, 3); //temporal reference for B-frame
+        skip_bits(&s->gb, 2); //dbquant
+    }
+
     /* PEI */
     while (get_bits1(&s->gb) != 0) {
         skip_bits(&s->gb, 8);
Index: libavcodec/mpegvideo.h
===================================================================
--- libavcodec/mpegvideo.h	(revision 16921)
+++ libavcodec/mpegvideo.h	(working copy)
@@ -201,6 +201,8 @@
     int bit_rate;     ///< wanted bit rate
     enum OutputFormat out_format; ///< output format
     int h263_pred;    ///< use mpeg4/h263 ac/dc predictions
+    int pb_frame;     ///< PB frame mode
+    int impr_pb_frame;///< improved PB frame mode
 
 /* the following codec id fields are deprecated in favor of codec_id */
     int h263_plus;    ///< h263 plus headers