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From: Michael Niedermayer <michael@niedermayer.cc>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: [FFmpeg-devel] [PATCH 9/9] avcodec/vlc: simplify min/maxbits in multi VLC
Date: Sun, 22 Oct 2023 23:51:13 +0200
Message-ID: <20231022215113.3469-9-michael@niedermayer.cc> (raw)
In-Reply-To: <20231022215113.3469-1-michael@niedermayer.cc>

nothing uses maxbits, so its removed
minbits is just the last entry (verified with assert on fate)

This basically reverts 58d9b5caf3d332c6495f9af437158bf45531a05e for the minbits computation

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/vlc.c | 13 ++++---------
 1 file changed, 4 insertions(+), 9 deletions(-)

diff --git a/libavcodec/vlc.c b/libavcodec/vlc.c
index ceabeba5408..de16424c93d 100644
--- a/libavcodec/vlc.c
+++ b/libavcodec/vlc.c
@@ -395,7 +395,7 @@ static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
                          const int is16bit, const int nb_codes, const int numbits,
                          VLCcode *buf, void *logctx)
 {
-    int minbits, maxbits, max;
+    int minbits, max;
     unsigned count[VLC_MULTI_MAX_SYMBOLS-1] = { 0, };
     VLC_MULTI_ELEM info = { { 0, }, 0, 0, };
     int count0 = 0;
@@ -407,14 +407,9 @@ static int vlc_multi_gen(VLC_MULTI_ELEM *table, const VLC *single,
         }
     }
 
-    minbits = 32;
-    maxbits = 0;
-
-    for (int n = nb_codes - count0; n < nb_codes; n++) {
-        minbits = FFMIN(minbits, buf[n].bits);
-        maxbits = FFMAX(maxbits, buf[n].bits);
-    }
-    av_assert0(maxbits <= numbits);
+    //This is only correct if count0 > 0 and the table is sorted
+    //minbits is not used if count0 == 0 and other parts assume the table is sorted too
+    minbits = buf[nb_codes - 1].bits;
 
     for (max = nb_codes; max > nb_codes - count0; max--) {
         // We can only add a code that fits with the shortest other code into the table
-- 
2.17.1

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  parent reply	other threads:[~2023-10-22 21:52 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-10-22 21:51 [FFmpeg-devel] [PATCH 1/9] avcodec/vlc: merge lost 16bit end of array check Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 2/9] avcodec/vlc: dont pass nb_elems into multi vlc code Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 3/9] avcodec/vlc: Skip subtable entries in multi VLC Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 4/9] avcodec/vlc: Replace mysterious max computation code in multi vlc Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 5/9] avcodec/vlc: Pass VLC_MULTI_ELEM directly not by pointer Michael Niedermayer
2023-10-23  6:10   ` Leo Izen
2023-10-23 16:04     ` Michael Niedermayer
2023-10-24  9:54       ` Leo Izen
2023-10-31 22:22         ` Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 6/9] avcodec/vlc: Remove mysterious jitter loop in multi VLC Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 7/9] Revert "avcodec/vlc: add correct upper limit for recursive function" Michael Niedermayer
2023-10-22 21:51 ` [FFmpeg-devel] [PATCH 8/9] Revert "avcodec/vlc: fix off by one in limit check for multi" Michael Niedermayer
2023-10-22 21:51 ` Michael Niedermayer [this message]
2023-10-22 23:02 ` [FFmpeg-devel] [PATCH 1/9] avcodec/vlc: merge lost 16bit end of array check Paul B Mahol
2023-10-23 16:05   ` Michael Niedermayer
2023-10-26 22:35 ` Michael Niedermayer

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