diff options
author | Måns Rullgård <mans@mansr.com> | 2009-09-29 14:38:27 +0400 |
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committer | Måns Rullgård <mans@mansr.com> | 2009-09-29 14:38:27 +0400 |
commit | c0d1463da71dc035776171a9165e4f65218b3654 (patch) | |
tree | 30cf6da8cccef054821268585363ff39ad5931ec /libavcodec/wmadec.c | |
parent | 4b4ac5c7a8b4c90c359ad7150ac71e542973abc8 (diff) |
WMA: use a table instead of pow() in decode_exp_vlc
Originally committed as revision 20076 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/wmadec.c')
-rw-r--r-- | libavcodec/wmadec.c | 77 |
1 files changed, 73 insertions, 4 deletions
diff --git a/libavcodec/wmadec.c b/libavcodec/wmadec.c index a4d5ad6d27..ce2940d24d 100644 --- a/libavcodec/wmadec.c +++ b/libavcodec/wmadec.c @@ -240,6 +240,74 @@ static void decode_exp_lsp(WMACodecContext *s, int ch) s->block_len, lsp_coefs); } +/** pow(10, i / 16.0) for i in -60..67 */ +static const float pow_tab[128] = { + 1.7782794100389e-04, 2.0535250264571e-04, + 2.3713737056617e-04, 2.7384196342644e-04, + 3.1622776601684e-04, 3.6517412725484e-04, + 4.2169650342858e-04, 4.8696752516586e-04, + 5.6234132519035e-04, 6.4938163157621e-04, + 7.4989420933246e-04, 8.6596432336006e-04, + 1.0000000000000e-03, 1.1547819846895e-03, + 1.3335214321633e-03, 1.5399265260595e-03, + 1.7782794100389e-03, 2.0535250264571e-03, + 2.3713737056617e-03, 2.7384196342644e-03, + 3.1622776601684e-03, 3.6517412725484e-03, + 4.2169650342858e-03, 4.8696752516586e-03, + 5.6234132519035e-03, 6.4938163157621e-03, + 7.4989420933246e-03, 8.6596432336006e-03, + 1.0000000000000e-02, 1.1547819846895e-02, + 1.3335214321633e-02, 1.5399265260595e-02, + 1.7782794100389e-02, 2.0535250264571e-02, + 2.3713737056617e-02, 2.7384196342644e-02, + 3.1622776601684e-02, 3.6517412725484e-02, + 4.2169650342858e-02, 4.8696752516586e-02, + 5.6234132519035e-02, 6.4938163157621e-02, + 7.4989420933246e-02, 8.6596432336007e-02, + 1.0000000000000e-01, 1.1547819846895e-01, + 1.3335214321633e-01, 1.5399265260595e-01, + 1.7782794100389e-01, 2.0535250264571e-01, + 2.3713737056617e-01, 2.7384196342644e-01, + 3.1622776601684e-01, 3.6517412725484e-01, + 4.2169650342858e-01, 4.8696752516586e-01, + 5.6234132519035e-01, 6.4938163157621e-01, + 7.4989420933246e-01, 8.6596432336007e-01, + 1.0000000000000e+00, 1.1547819846895e+00, + 1.3335214321633e+00, 1.5399265260595e+00, + 1.7782794100389e+00, 2.0535250264571e+00, + 2.3713737056617e+00, 2.7384196342644e+00, + 3.1622776601684e+00, 3.6517412725484e+00, + 4.2169650342858e+00, 4.8696752516586e+00, + 5.6234132519035e+00, 6.4938163157621e+00, + 7.4989420933246e+00, 8.6596432336007e+00, + 1.0000000000000e+01, 1.1547819846895e+01, + 1.3335214321633e+01, 1.5399265260595e+01, + 1.7782794100389e+01, 2.0535250264571e+01, + 2.3713737056617e+01, 2.7384196342644e+01, + 3.1622776601684e+01, 3.6517412725484e+01, + 4.2169650342858e+01, 4.8696752516586e+01, + 5.6234132519035e+01, 6.4938163157621e+01, + 7.4989420933246e+01, 8.6596432336007e+01, + 1.0000000000000e+02, 1.1547819846895e+02, + 1.3335214321633e+02, 1.5399265260595e+02, + 1.7782794100389e+02, 2.0535250264571e+02, + 2.3713737056617e+02, 2.7384196342644e+02, + 3.1622776601684e+02, 3.6517412725484e+02, + 4.2169650342858e+02, 4.8696752516586e+02, + 5.6234132519035e+02, 6.4938163157621e+02, + 7.4989420933246e+02, 8.6596432336007e+02, + 1.0000000000000e+03, 1.1547819846895e+03, + 1.3335214321633e+03, 1.5399265260595e+03, + 1.7782794100389e+03, 2.0535250264571e+03, + 2.3713737056617e+03, 2.7384196342644e+03, + 3.1622776601684e+03, 3.6517412725484e+03, + 4.2169650342858e+03, 4.8696752516586e+03, + 5.6234132519035e+03, 6.4938163157621e+03, + 7.4989420933246e+03, 8.6596432336007e+03, + 1.0000000000000e+04, 1.1547819846895e+04, + 1.3335214321633e+04, 1.5399265260595e+04, +}; + /** * decode exponents coded with VLC codes */ @@ -248,6 +316,7 @@ static int decode_exp_vlc(WMACodecContext *s, int ch) int last_exp, n, code; const uint16_t *ptr; float v, *q, max_scale, *q_end; + const float *ptab = pow_tab + 60; ptr = s->exponent_bands[s->frame_len_bits - s->block_len_bits]; q = s->exponents[ch]; @@ -255,8 +324,7 @@ static int decode_exp_vlc(WMACodecContext *s, int ch) max_scale = 0; if (s->version == 1) { last_exp = get_bits(&s->gb, 5) + 10; - /* XXX: use a table */ - v = pow(10, last_exp * (1.0 / 16.0)); + v = ptab[last_exp]; max_scale = v; n = *ptr++; do { @@ -271,8 +339,9 @@ static int decode_exp_vlc(WMACodecContext *s, int ch) return -1; /* NOTE: this offset is the same as MPEG4 AAC ! */ last_exp += code - 60; - /* XXX: use a table */ - v = pow(10, last_exp * (1.0 / 16.0)); + if ((unsigned)last_exp + 60 > FF_ARRAY_ELEMS(pow_tab)) + return -1; + v = ptab[last_exp]; if (v > max_scale) max_scale = v; n = *ptr++; |