diff options
| author | Janne Grunau <janne-libav@jannau.net> | 2014-02-21 13:13:36 +0100 |
|---|---|---|
| committer | Janne Grunau <janne-libav@jannau.net> | 2014-02-28 13:00:48 +0100 |
| commit | 7686afd049be98d18663682b92d983340fa2c305 (patch) | |
| tree | e50dd1c93c3eef3bdb920b223bfcbb900816c915 /libavcodec/dcadec.c | |
| parent | 08e3ea60ff4059341b74be04a428a38f7c3630b0 (diff) | |
| download | ffmpeg-7686afd049be98d18663682b92d983340fa2c305.tar.gz | |
dca: factorize scaling in inverse ADPCM
Based on a patch from Christophe Gisquet.
Unrolling of the m == 0 case avoids a possible use of the uninitilized
value sum when s->predictor_history is not set. I failed to find a
sample for it. It also reduced the cycle count from 220 to 150 on
sandy bridge, x86_64 linux, gcc 4.8.2 compared to his patch.
Diffstat (limited to 'libavcodec/dcadec.c')
| -rw-r--r-- | libavcodec/dcadec.c | 27 |
1 files changed, 19 insertions, 8 deletions
diff --git a/libavcodec/dcadec.c b/libavcodec/dcadec.c index c251db80a9..5ede61db33 100644 --- a/libavcodec/dcadec.c +++ b/libavcodec/dcadec.c @@ -1192,16 +1192,27 @@ static int dca_subsubframe(DCAContext *s, int base_channel, int block_index) */ if (s->prediction_mode[k][l]) { int n; - for (m = 0; m < 8; m++) { - for (n = 1; n <= 4; n++) + if (s->predictor_history) + subband_samples[k][l][0] += (adpcm_vb[s->prediction_vq[k][l]][0] * + s->subband_samples_hist[k][l][3] + + adpcm_vb[s->prediction_vq[k][l]][1] * + s->subband_samples_hist[k][l][2] + + adpcm_vb[s->prediction_vq[k][l]][2] * + s->subband_samples_hist[k][l][1] + + adpcm_vb[s->prediction_vq[k][l]][3] * + s->subband_samples_hist[k][l][0]) * + (1.0f / 8192); + for (m = 1; m < 8; m++) { + float sum = adpcm_vb[s->prediction_vq[k][l]][0] * + subband_samples[k][l][m - 1]; + for (n = 2; n <= 4; n++) if (m >= n) - subband_samples[k][l][m] += - (adpcm_vb[s->prediction_vq[k][l]][n - 1] * - subband_samples[k][l][m - n] / 8192); + sum += adpcm_vb[s->prediction_vq[k][l]][n - 1] * + subband_samples[k][l][m - n]; else if (s->predictor_history) - subband_samples[k][l][m] += - (adpcm_vb[s->prediction_vq[k][l]][n - 1] * - s->subband_samples_hist[k][l][m - n + 4] / 8192); + sum += adpcm_vb[s->prediction_vq[k][l]][n - 1] * + s->subband_samples_hist[k][l][m - n + 4]; + subband_samples[k][l][m] += sum * 1.0f / 8192; } } } |