Convert floating-point MDCT coefficients to 24-bit fixed-point all at once

instead of doing it separately in 2 different functions.
This makes float AC-3 encoding approx. 3-7% faster overall.
Also, the coefficient conversion can now be easily SIMD-optimized.

Originally committed as revision 26232 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 11 insertions, 0 deletions

diff --git a/libavcodec/ac3enc_float.c b/libavcodec/ac3enc_float.c
index 82d806bc06..f3246362e7 100644
--- a/libavcodec/ac3enc_float.c
+++ b/libavcodec/ac3enc_float.c
@@ -102,6 +102,17 @@ static int normalize_samples(AC3EncodeContext *s)
 }
 
 
+/**
+ * Scale MDCT coefficients from float to 24-bit fixed-point.
+ */
+static void scale_coefficients(AC3EncodeContext *s)
+{
+    int i;
+    for (i = 0; i < AC3_MAX_COEFS * AC3_MAX_BLOCKS * s->channels; i++)
+        s->fixed_coef_buffer[i] = SCALE_FLOAT(s->mdct_coef_buffer[i], 24);
+}
+
+
 AVCodec ac3_encoder = {
     "ac3",
     AVMEDIA_TYPE_AUDIO,