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| author | Thilo Borgmann <thilo.borgmann@googlemail.com> | 2010-01-07 22:23:28 +0000 |
|---|---|---|
| committer | Thilo Borgmann <thilo.borgmann@googlemail.com> | 2010-01-07 22:23:28 +0000 |
| commit | 99c5f5ccbefba0caa39020e58bcb458e107f8e89 (patch) | |
| tree | 26c0b2ae244b929dc0bbd3f3bd99cf516686ce92 /libavcodec/alsdec.c | |
| parent | 9a02c3e1833ef933f03860b5ac31ebdda1e1912d (diff) | |
| download | ffmpeg-99c5f5ccbefba0caa39020e58bcb458e107f8e89.tar.gz | |
Optimize short-term prediction by reducing index arithmetic.
Originally committed as revision 21069 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/alsdec.c')
| -rw-r--r-- | libavcodec/alsdec.c | 25 |
1 files changed, 19 insertions, 6 deletions
diff --git a/libavcodec/alsdec.c b/libavcodec/alsdec.c index dd3278de5e..11d315b4bf 100644 --- a/libavcodec/alsdec.c +++ b/libavcodec/alsdec.c @@ -712,6 +712,8 @@ static int decode_var_block_data(ALSDecContext *ctx, ALSBlockData *bd) int32_t *quant_cof = bd->quant_cof; int32_t *lpc_cof = bd->lpc_cof; int32_t *raw_samples = bd->raw_samples; + int32_t *raw_samples_end = bd->raw_samples + bd->block_length; + int32_t lpc_cof_reversed[opt_order]; // reverse long-term prediction if (*bd->use_ltp) { @@ -739,9 +741,9 @@ static int decode_var_block_data(ALSDecContext *ctx, ALSBlockData *bd) y = 1 << 19; for (sb = 0; sb < smp; sb++) - y += MUL64(lpc_cof[sb], *(raw_samples + smp - (sb + 1))); + y += MUL64(lpc_cof[sb], raw_samples[-(sb + 1)]); - raw_samples[smp] -= y >> 20; + *raw_samples++ -= y >> 20; parcor_to_lpc(smp, quant_cof, lpc_cof); } } else { @@ -775,16 +777,27 @@ static int decode_var_block_data(ALSDecContext *ctx, ALSBlockData *bd) raw_samples[sb] >>= bd->shift_lsbs; } + // reverse linear prediction coefficients for efficiency + lpc_cof = lpc_cof + opt_order; + + for (sb = 0; sb < opt_order; sb++) + lpc_cof_reversed[sb] = lpc_cof[-(sb + 1)]; + // reconstruct raw samples - for (; smp < bd->block_length; smp++) { + raw_samples = bd->raw_samples + smp; + lpc_cof = lpc_cof_reversed + opt_order; + + for (; raw_samples < raw_samples_end; raw_samples++) { y = 1 << 19; - for (sb = 0; sb < opt_order; sb++) - y += MUL64(bd->lpc_cof[sb], *(raw_samples + smp - (sb + 1))); + for (sb = -opt_order; sb < 0; sb++) + y += MUL64(lpc_cof[sb], raw_samples[sb]); - raw_samples[smp] -= y >> 20; + *raw_samples -= y >> 20; } + raw_samples = bd->raw_samples; + // restore previous samples in case that they have been altered if (bd->store_prev_samples) memcpy(raw_samples - sconf->max_order, bd->prev_raw_samples, |