[FFmpeg-cvslog] avcodec/mpeg4videodec: Avoid unnecessary indirections

[Andreas Rheinhardt]

ffmpeg | branch: master | Andreas Rheinhardt <andreas.rheinhardt at outlook.com> | Thu Jun 19 15:50:32 2025 +0200| [91e9578025f8b251e2f56a8d06297344ae89464e] | committer: Andreas Rheinhardt

avcodec/mpeg4videodec: Avoid unnecessary indirections

This basically reverts d4967c04e040b3b2f937cad88599af825147ec94.
Said commit was based on the false premise that it would
be an aliasing violation to upcast a pointer to structure
to a pointer to a bigger structure containing the original
structure as its first element, but this is just not true.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=91e9578025f8b251e2f56a8d06297344ae89464e
---

 libavcodec/mpeg4videodec.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/libavcodec/mpeg4videodec.c b/libavcodec/mpeg4videodec.c
index 34f383bbbd..c61fd23c48 100644
--- a/libavcodec/mpeg4videodec.c
+++ b/libavcodec/mpeg4videodec.c
@@ -1647,12 +1647,10 @@ not_coded:
  */
 static int mpeg4_decode_partitioned_mb(MpegEncContext *s, int16_t block[6][64])
 {
-    Mpeg4DecContext *ctx = s->avctx->priv_data;
+    Mpeg4DecContext *const ctx = (Mpeg4DecContext*)s;
     int cbp, mb_type, use_intra_dc_vlc;
     const int xy = s->mb_x + s->mb_y * s->mb_stride;
 
-    av_assert2(s == (void*)ctx);
-
     mb_type = s->cur_pic.mb_type[xy];
     cbp     = s->cbp_table[xy];
 
@@ -1737,13 +1735,12 @@ static int mpeg4_decode_partitioned_mb(MpegEncContext *s, int16_t block[6][64])
 
 static int mpeg4_decode_mb(MpegEncContext *s, int16_t block[6][64])
 {
-    Mpeg4DecContext *ctx = s->avctx->priv_data;
+    Mpeg4DecContext *const ctx = (Mpeg4DecContext*)s;
     int cbpc, cbpy, i, cbp, pred_x, pred_y, mx, my, dquant;
     static const int8_t quant_tab[4] = { -1, -2, 1, 2 };
     const int xy = s->mb_x + s->mb_y * s->mb_stride;
     int next;
 
-    av_assert2(s ==  (void*)ctx);
     av_assert2(s->h263_pred);
 
     if (s->pict_type == AV_PICTURE_TYPE_P ||
@@ -2153,7 +2150,7 @@ static const uint8_t ac_state_tab[22][2] =
 
 static int mpeg4_decode_studio_block(MpegEncContext *s, int32_t block[64], int n)
 {
-    Mpeg4DecContext *ctx = s->avctx->priv_data;
+    Mpeg4DecContext *const ctx = (Mpeg4DecContext*)s;
 
     int cc, dct_dc_size, dct_diff, code, j, idx = 1, group = 0, run = 0,
         additional_code_len, sign, mismatch;