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| author | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | 2020-06-26 11:36:57 +0200 |
|---|---|---|
| committer | Andreas Rheinhardt <andreas.rheinhardt@gmail.com> | 2020-09-18 02:11:34 +0200 |
| commit | b2c42f02337301583b51bea2ede9dbfd837991c0 (patch) | |
| tree | dfacb04223b14b1b4c3aeec7dd62e39799462a3a | |
| parent | 010e345afe5d9744956dbc6253a4999e6851e7e9 (diff) | |
| download | ffmpeg-b2c42f02337301583b51bea2ede9dbfd837991c0.tar.gz | |
avcodec/smacker: Use unsigned for prediction values
Up until now, the Smacker decoder has pretended that the prediction
values are signed in code like 'pred[0] += (unsigned)sign_extend(val, 16)'
(the cast has been added to this code later to fix undefined behaviour).
This has been even done in case the PCM format is u8.
Yet in case of 8/16 bit samples, only the lower 8/16 bit of the predicition
values are ever used, so one can just as well just use unsigned and
remove the sign extensions. This is what this commit does.
For GCC 9 the time for one call to smka_decode_frame() for the sample from
ticket #2425 decreased from 1709043 to 1693619 decicycles; for Clang 9
it went up from 1355273 to 1369089 decicycles.
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
| -rw-r--r-- | libavcodec/smacker.c | 13 |
1 files changed, 6 insertions, 7 deletions
diff --git a/libavcodec/smacker.c b/libavcodec/smacker.c index e588b03820..d2b1c68162 100644 --- a/libavcodec/smacker.c +++ b/libavcodec/smacker.c @@ -595,11 +595,10 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, int16_t *samples; uint8_t *samples8; uint8_t values[4]; - int val; int i, res, ret; int unp_size; int bits, stereo; - int pred[2] = {0, 0}; + unsigned pred[2], val; if (buf_size <= 4) { av_log(avctx, AV_LOG_ERROR, "packet is too small\n"); @@ -668,7 +667,7 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, /* this codec relies on wraparound instead of clipping audio */ if(bits) { //decode 16-bit data for(i = stereo; i >= 0; i--) - pred[i] = sign_extend(av_bswap16(get_bits(&gb, 16)), 16); + pred[i] = av_bswap16(get_bits(&gb, 16)); for(i = 0; i <= stereo; i++) *samples++ = pred[i]; for(; i < unp_size / 2; i++) { @@ -687,7 +686,7 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, else res = values[3]; val |= res << 8; - pred[1] += (unsigned)sign_extend(val, 16); + pred[1] += val; *samples++ = pred[1]; } else { if(vlc[0].table) @@ -700,7 +699,7 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, else res = values[1]; val |= res << 8; - pred[0] += (unsigned)sign_extend(val, 16); + pred[0] += val; *samples++ = pred[0]; } } @@ -719,14 +718,14 @@ static int smka_decode_frame(AVCodecContext *avctx, void *data, res = get_vlc2(&gb, vlc[1].table, SMKTREE_BITS, 3); else res = values[1]; - pred[1] += sign_extend(res, 8); + pred[1] += res; *samples8++ = pred[1]; } else { if(vlc[0].table) res = get_vlc2(&gb, vlc[0].table, SMKTREE_BITS, 3); else res = values[0]; - pred[0] += sign_extend(res, 8); + pred[0] += res; *samples8++ = pred[0]; } } |