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| author | Siarhei Siamashka <siarhei.siamashka@gmail.com> | 2009-05-16 14:17:08 +0000 |
|---|---|---|
| committer | Siarhei Siamashka <siarhei.siamashka@gmail.com> | 2009-05-16 14:17:08 +0000 |
| commit | 7d485f165f7f6313002da1fe67c2742f0fbb16c9 (patch) | |
| tree | 87e68249904f3c5bc7dcfc05df2eea10fd318ea2 /libavcodec/mdct.c | |
| parent | 3ac56e28b0a3fc84ccac9ac7e359f0f29567f8a0 (diff) | |
| download | ffmpeg-7d485f165f7f6313002da1fe67c2742f0fbb16c9.tar.gz | |
Support for getting (i)MDCT output multiplied by a constant scaling factor.
Scaling (i)MDCT output has no runtime overhead and can be used to improve
performance of audio codecs. All the changes are only needed in
'ff_mdct_init' function and slow down initialization a bit.
Originally committed as revision 18855 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec/mdct.c')
| -rw-r--r-- | libavcodec/mdct.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/libavcodec/mdct.c b/libavcodec/mdct.c index 7bd4d77f68..8a42adb4f3 100644 --- a/libavcodec/mdct.c +++ b/libavcodec/mdct.c @@ -68,10 +68,10 @@ av_cold void ff_sine_window_init(float *window, int n) { /** * init MDCT or IMDCT computation. */ -av_cold int ff_mdct_init(MDCTContext *s, int nbits, int inverse) +av_cold int ff_mdct_init(MDCTContext *s, int nbits, int inverse, double scale) { int n, n4, i; - double alpha; + double alpha, theta; memset(s, 0, sizeof(*s)); n = 1 << nbits; @@ -85,10 +85,12 @@ av_cold int ff_mdct_init(MDCTContext *s, int nbits, int inverse) if (!s->tsin) goto fail; + theta = 1.0 / 8.0 + (scale < 0 ? n4 : 0); + scale = sqrt(fabs(scale)); for(i=0;i<n4;i++) { - alpha = 2 * M_PI * (i + 1.0 / 8.0) / n; - s->tcos[i] = -cos(alpha); - s->tsin[i] = -sin(alpha); + alpha = 2 * M_PI * (i + theta) / n; + s->tcos[i] = -cos(alpha) * scale; + s->tsin[i] = -sin(alpha) * scale; } if (ff_fft_init(&s->fft, s->nbits - 2, inverse) < 0) goto fail; |