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[FFmpeg-devel,54/57] avcodec/mpeg12dec: Don't initialize inter_scantable

Message ID AS8P250MB0744BC0F8E5E5C6F6F5FAC378F1B2@AS8P250MB0744.EURP250.PROD.OUTLOOK.COM
State New
Headers show
Series [FFmpeg-devel,01/14] avcodec/get_buffer: Remove redundant check | expand

Commit Message

Andreas Rheinhardt April 29, 2024, 9:14 p.m. UTC 
MPEG-1/2 only needs one scantable and therefore all code
already uses the intra one. So stop initializing
the inter one altogether.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
---
 libavcodec/mpeg12dec.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)
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Patch

diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index 52f98986f6..55e3a31e95 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -1256,13 +1256,10 @@  static int mpeg_decode_picture_coding_extension(Mpeg1Context *s1)
     s->chroma_420_type            = get_bits1(&s->gb);
     s->progressive_frame          = get_bits1(&s->gb);
 
-    if (s->alternate_scan) {
-        ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable, ff_alternate_vertical_scan);
-        ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable, ff_alternate_vertical_scan);
-    } else {
-        ff_init_scantable(s->idsp.idct_permutation, &s->inter_scantable, ff_zigzag_direct);
-        ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable, ff_zigzag_direct);
-    }
+    // We only initialize intra_scantable, as both scantables always coincide
+    // and all code therefore only uses the intra one.
+    ff_init_scantable(s->idsp.idct_permutation, &s->intra_scantable,
+                      s->alternate_scan ? ff_alternate_vertical_scan : ff_zigzag_direct);
 
     /* composite display not parsed */
     ff_dlog(s->avctx, "intra_dc_precision=%d\n", s->intra_dc_precision);