avcodec/vc1: factor read_bfraction() out

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/vc1.c

@@ -613,6 +613,12 @@ static void rotate_luts(VC1Context *v)
     *v->curr_use_ic = 0;
 }
 
+static int read_bfraction(VC1Context *v, GetBitContext* gb) {
+    v->bfraction_lut_index = get_vlc2(gb, ff_vc1_bfraction_vlc.table, VC1_BFRACTION_VLC_BITS, 1);
+    v->bfraction           = ff_vc1_bfraction_lut[v->bfraction_lut_index];
+    return 0;
+}
+
 int ff_vc1_parse_frame_header(VC1Context *v, GetBitContext* gb)
 {
     int pqindex, lowquant, status;
@@ -644,8 +650,8 @@ int ff_vc1_parse_frame_header(VC1Context *v, GetBitContext* gb)
 
     v->bi_type = 0;
     if (v->s.pict_type == AV_PICTURE_TYPE_B) {
-        v->bfraction_lut_index = get_vlc2(gb, ff_vc1_bfraction_vlc.table, VC1_BFRACTION_VLC_BITS, 1);
-        v->bfraction           = ff_vc1_bfraction_lut[v->bfraction_lut_index];
+        if (read_bfraction(v, gb) < 0)
+            return AVERROR_INVALIDDATA;
         if (v->bfraction == 0) {
             v->s.pict_type = AV_PICTURE_TYPE_BI;
         }
@@ -928,8 +934,8 @@ int ff_vc1_parse_frame_header_adv(VC1Context *v, GetBitContext* gb)
                 v->refdist += get_unary(gb, 0, 16);
         }
         if ((v->s.pict_type == AV_PICTURE_TYPE_B) || (v->s.pict_type == AV_PICTURE_TYPE_BI)) {
-            v->bfraction_lut_index = get_vlc2(gb, ff_vc1_bfraction_vlc.table, VC1_BFRACTION_VLC_BITS, 1);
-            v->bfraction           = ff_vc1_bfraction_lut[v->bfraction_lut_index];
+            if (read_bfraction(v, gb) < 0)
+                return AVERROR_INVALIDDATA;
             v->frfd = (v->bfraction * v->refdist) >> 8;
             v->brfd = v->refdist - v->frfd - 1;
             if (v->brfd < 0)
@@ -941,8 +947,8 @@ int ff_vc1_parse_frame_header_adv(VC1Context *v, GetBitContext* gb)
         if (v->finterpflag)
             v->interpfrm = get_bits1(gb);
         if (v->s.pict_type == AV_PICTURE_TYPE_B) {
-            v->bfraction_lut_index = get_vlc2(gb, ff_vc1_bfraction_vlc.table, VC1_BFRACTION_VLC_BITS, 1);
-            v->bfraction           = ff_vc1_bfraction_lut[v->bfraction_lut_index];
+            if (read_bfraction(v, gb) < 0)
+                return AVERROR_INVALIDDATA;
             if (v->bfraction == 0) {
                 v->s.pict_type = AV_PICTURE_TYPE_BI; /* XXX: should not happen here */
             }
@@ -1186,8 +1192,8 @@ int ff_vc1_parse_frame_header_adv(VC1Context *v, GetBitContext* gb)
         break;
     case AV_PICTURE_TYPE_B:
         if (v->fcm == ILACE_FRAME) {
-            v->bfraction_lut_index = get_vlc2(gb, ff_vc1_bfraction_vlc.table, VC1_BFRACTION_VLC_BITS, 1);
-            v->bfraction           = ff_vc1_bfraction_lut[v->bfraction_lut_index];
+            if (read_bfraction(v, gb) < 0)
+                return AVERROR_INVALIDDATA;
             if (v->bfraction == 0) {
                 return -1;
             }