[FFmpeg-devel] [PATCH 13/39] avcodec/msmpeg4dec: Reuse identical MV VLC

[Andreas Rheinhardt]

msmpeg4dec and ituh263dec both create VLCs with identical parameters out
of ff_mvtab. Given that ff_msmpeg4_decode_init() always (indirectly) calls
ff_h263_decode_init_vlc(), the VLC initialized by the latter can be
directly used by msmpeg4dec. Doing so saves a bit more than 2KB from the
.bss segment as well as the code to initialize a VLC.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/h263.h       | 2 ++
 libavcodec/ituh263dec.c | 7 +++----
 libavcodec/msmpeg4dec.c | 7 +------
 3 files changed, 6 insertions(+), 10 deletions(-)

diff --git a/libavcodec/h263.h b/libavcodec/h263.h
index f891f72379..998f7d0d59 100644
--- a/libavcodec/h263.h
+++ b/libavcodec/h263.h
@@ -34,6 +34,7 @@
 // reading vlc values. Changing these may improve speed and data cache needs
 // be aware though that decreasing them may need the number of stages that is
 // passed to get_vlc* to be increased.
+#define H263_MV_VLC_BITS     9
 #define INTRA_MCBPC_VLC_BITS 6
 #define INTER_MCBPC_VLC_BITS 7
 #define CBPY_VLC_BITS 6
@@ -44,6 +45,7 @@
 extern VLC ff_h263_intra_MCBPC_vlc;
 extern VLC ff_h263_inter_MCBPC_vlc;
 extern VLC ff_h263_cbpy_vlc;
+extern VLC ff_h263_mv_vlc;
 
 extern const enum AVPixelFormat ff_h263_hwaccel_pixfmt_list_420[];
 
diff --git a/libavcodec/ituh263dec.c b/libavcodec/ituh263dec.c
index 7ddb33b795..eec86c81b1 100644
--- a/libavcodec/ituh263dec.c
+++ b/libavcodec/ituh263dec.c
@@ -51,7 +51,6 @@
 // reading vlc values. Changing these may improve speed and data cache needs
 // be aware though that decreasing them may need the number of stages that is
 // passed to get_vlc* to be increased.
-#define MV_VLC_BITS 9
 #define H263_MBTYPE_B_VLC_BITS 6
 #define CBPC_B_VLC_BITS 3
 
@@ -98,7 +97,7 @@ void ff_h263_show_pict_info(MpegEncContext *s){
 VLC ff_h263_intra_MCBPC_vlc;
 VLC ff_h263_inter_MCBPC_vlc;
 VLC ff_h263_cbpy_vlc;
-static VLC mv_vlc;
+VLC ff_h263_mv_vlc;
 static VLC h263_mbtype_b_vlc;
 static VLC cbpc_b_vlc;
 
@@ -119,7 +118,7 @@ av_cold void ff_h263_decode_init_vlc(void)
         INIT_VLC_STATIC(&ff_h263_cbpy_vlc, CBPY_VLC_BITS, 16,
                  &ff_h263_cbpy_tab[0][1], 2, 1,
                  &ff_h263_cbpy_tab[0][0], 2, 1, 64);
-        INIT_VLC_STATIC(&mv_vlc, MV_VLC_BITS, 33,
+        INIT_VLC_STATIC(&ff_h263_mv_vlc, H263_MV_VLC_BITS, 33,
                  &ff_mvtab[0][1], 2, 1,
                  &ff_mvtab[0][0], 2, 1, 538);
         ff_rl_init(&ff_h263_rl_inter, ff_h263_static_rl_table_store[0]);
@@ -270,7 +269,7 @@ int ff_h263_resync(MpegEncContext *s){
 int ff_h263_decode_motion(MpegEncContext * s, int pred, int f_code)
 {
     int code, val, sign, shift;
-    code = get_vlc2(&s->gb, mv_vlc.table, MV_VLC_BITS, 2);
+    code = get_vlc2(&s->gb, ff_h263_mv_vlc.table, H263_MV_VLC_BITS, 2);
 
     if (code == 0)
         return pred;
diff --git a/libavcodec/msmpeg4dec.c b/libavcodec/msmpeg4dec.c
index 06e9707b65..d059e8eecc 100644
--- a/libavcodec/msmpeg4dec.c
+++ b/libavcodec/msmpeg4dec.c
@@ -38,7 +38,6 @@
 #define V2_INTRA_CBPC_VLC_BITS 3
 #define V2_MB_TYPE_VLC_BITS 7
 #define MV_VLC_BITS 9
-#define V2_MV_VLC_BITS 9
 #define TEX_VLC_BITS 9
 
 #define DEFAULT_INTER_INDEX 3
@@ -66,7 +65,6 @@ static VLC v2_dc_lum_vlc;
 static VLC v2_dc_chroma_vlc;
 static VLC v2_intra_cbpc_vlc;
 static VLC v2_mb_type_vlc;
-static VLC v2_mv_vlc;
 VLC ff_inter_intra_vlc;
 
 /* This is identical to H.263 except that its range is multiplied by 2. */
@@ -74,7 +72,7 @@ static int msmpeg4v2_decode_motion(MpegEncContext * s, int pred, int f_code)
 {
     int code, val, sign, shift;
 
-    code = get_vlc2(&s->gb, v2_mv_vlc.table, V2_MV_VLC_BITS, 2);
+    code = get_vlc2(&s->gb, ff_h263_mv_vlc.table, H263_MV_VLC_BITS, 2);
     ff_dlog(s, "MV code %d at %d %d pred: %d\n", code, s->mb_x,s->mb_y, pred);
     if (code < 0)
         return 0xffff;
@@ -362,9 +360,6 @@ av_cold int ff_msmpeg4_decode_init(AVCodecContext *avctx)
         INIT_VLC_STATIC(&v2_mb_type_vlc, V2_MB_TYPE_VLC_BITS, 8,
                  &ff_v2_mb_type[0][1], 2, 1,
                  &ff_v2_mb_type[0][0], 2, 1, 128);
-        INIT_VLC_STATIC(&v2_mv_vlc, V2_MV_VLC_BITS, 33,
-                 &ff_mvtab[0][1], 2, 1,
-                 &ff_mvtab[0][0], 2, 1, 538);
 
         INIT_VLC_STATIC(&ff_mb_non_intra_vlc[0], MB_NON_INTRA_VLC_BITS, 128,
                      &ff_wmv2_inter_table[0][0][1], 8, 4,
-- 
2.25.1