diff options
author | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | 2020-07-25 15:14:53 +0200 |
---|---|---|
committer | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | 2020-09-18 02:00:34 +0200 |
commit | 3899adc29869301bfab77a9064a21da7a5a5163d (patch) | |
tree | c9ddd548b30c64a068a03823fd3e70a0d8fe6fe7 /libavcodec/smacker.c | |
parent | 943a4581570728b4b1a2bf97e5601e24f3f80404 (diff) |
avcodec/smacker: Remove redundant checks when reading VLC codes
The VLC codes in question originate from a Huffmann tree and so every
sequence of bits that is longer than the longest code contains an
initial sequence that is a valid code. Given that it has been checked
during reading said tree (and once again in ff_init_vlc_sparse()) that
the length of each code is <= 3 * the number of bits read at once when
reading codes, get_vlc2() will always find a matching entry.
These checks have been added in 71d3c25a7ef442ac2dd7b6fbf7c489ebc0b58e9b
at a time when the length of the codes had not been checked when parsing
the tree.
For GCC 9 and the sample from ticket #2425 this led to a slight
performance regression: The time for one call to smka_decode_frame()
increased from 2053671 to 2064529 decicycles; for Clang 9, performance
improved from 1521288 to 1508459 decicycles.
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Diffstat (limited to 'libavcodec/smacker.c')
-rw-r--r-- | libavcodec/smacker.c | 32 |
1 files changed, 0 insertions, 32 deletions
diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c index 991622eb0e..5e1b8c59ff 100644 --- a/libavcodec/smacker.c +++ b/libavcodec/smacker.c @@ -140,8 +140,6 @@ static int smacker_decode_bigtree(GetBitContext *gb, HuffContext *hc, int val, i1, i2; i1 = ctx->v1->table ? get_vlc2(gb, ctx->v1->table, SMKTREE_BITS, 3) : 0; i2 = ctx->v2->table ? get_vlc2(gb, ctx->v2->table, SMKTREE_BITS, 3) : 0; - if (i1 < 0 || i2 < 0) - return AVERROR_INVALIDDATA; val = ctx->recode1[i1] | (ctx->recode2[i2] << 8); if(val == ctx->escapes[0]) { ctx->last[0] = hc->current; @@ -678,21 +676,11 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, res = get_vlc2(&gb, vlc[2].table, SMKTREE_BITS, 3); else res = 0; - if (res < 0) { - av_log(avctx, AV_LOG_ERROR, "invalid vlc\n"); - ret = AVERROR_INVALIDDATA; - goto error; - } val = h[2].values[res]; if(vlc[3].table) res = get_vlc2(&gb, vlc[3].table, SMKTREE_BITS, 3); else res = 0; - if (res < 0) { - av_log(avctx, AV_LOG_ERROR, "invalid vlc\n"); - ret = AVERROR_INVALIDDATA; - goto error; - } val |= h[3].values[res] << 8; pred[1] += (unsigned)sign_extend(val, 16); *samples++ = pred[1]; @@ -701,21 +689,11 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3); else res = 0; - if (res < 0) { - av_log(avctx, AV_LOG_ERROR, "invalid vlc\n"); - ret = AVERROR_INVALIDDATA; - goto error; - } val = h[0].values[res]; if(vlc[1].table) res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3); else res = 0; - if (res < 0) { - av_log(avctx, AV_LOG_ERROR, "invalid vlc\n"); - ret = AVERROR_INVALIDDATA; - goto error; - } val |= h[1].values[res] << 8; pred[0] += (unsigned)sign_extend(val, 16); *samples++ = pred[0]; @@ -736,11 +714,6 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3); else res = 0; - if (res < 0) { - av_log(avctx, AV_LOG_ERROR, "invalid vlc\n"); - ret = AVERROR_INVALIDDATA; - goto error; - } pred[1] += sign_extend(h[1].values[res], 8); *samples8++ = pred[1]; } else { @@ -748,11 +721,6 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3); else res = 0; - if (res < 0) { - av_log(avctx, AV_LOG_ERROR, "invalid vlc\n"); - ret = AVERROR_INVALIDDATA; - goto error; - } pred[0] += sign_extend(h[0].values[res], 8); *samples8++ = pred[0]; } |