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author | Justin Ruggles <justin.ruggles@gmail.com> | 2008-03-01 15:48:18 +0000 |
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committer | Justin Ruggles <justin.ruggles@gmail.com> | 2008-03-01 15:48:18 +0000 |
commit | 9d10e6e6c0577c67fa0e0309240b10597ea29ded (patch) | |
tree | dcc27d94bf94d613a08b6cab441f3d0474e5d4a9 /libavcodec | |
parent | 8541cc274cc2f6839f6677bc795e32ac7ea915d2 (diff) | |
download | ffmpeg-streaming-9d10e6e6c0577c67fa0e0309240b10597ea29ded.zip ffmpeg-streaming-9d10e6e6c0577c67fa0e0309240b10597ea29ded.tar.gz |
pre-calculate downmix coefficient sums. 2% faster 5.1-to-stereo downmixing.
Originally committed as revision 12286 to svn://svn.ffmpeg.org/ffmpeg/trunk
Diffstat (limited to 'libavcodec')
-rw-r--r-- | libavcodec/ac3dec.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c index 6c725c4..e205ef4 100644 --- a/libavcodec/ac3dec.c +++ b/libavcodec/ac3dec.c @@ -154,6 +154,7 @@ typedef struct { int center_mix_level; ///< Center mix level index int surround_mix_level; ///< Surround mix level index float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients + float downmix_coeff_sum[2]; ///< sum of downmix coeffs for each output channel float dynamic_range[2]; ///< dynamic range int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates int num_cpl_bands; ///< number of coupling bands @@ -402,6 +403,12 @@ static void set_downmix_coeffs(AC3DecodeContext *s) int nf = s->channel_mode - 4; s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix; } + + s->downmix_coeff_sum[0] = s->downmix_coeff_sum[1] = 0.0f; + for(i=0; i<s->fbw_channels; i++) { + s->downmix_coeff_sum[0] += s->downmix_coeffs[i][0]; + s->downmix_coeff_sum[1] += s->downmix_coeffs[i][1]; + } } /** @@ -732,18 +739,16 @@ static inline void do_imdct(AC3DecodeContext *s) static void ac3_downmix(AC3DecodeContext *s) { int i, j; - float v0, v1, s0, s1; + float v0, v1; for(i=0; i<256; i++) { - v0 = v1 = s0 = s1 = 0.0f; + v0 = v1 = 0.0f; for(j=0; j<s->fbw_channels; j++) { v0 += s->output[j][i] * s->downmix_coeffs[j][0]; v1 += s->output[j][i] * s->downmix_coeffs[j][1]; - s0 += s->downmix_coeffs[j][0]; - s1 += s->downmix_coeffs[j][1]; } - v0 /= s0; - v1 /= s1; + v0 /= s->downmix_coeff_sum[0]; + v1 /= s->downmix_coeff_sum[1]; if(s->output_mode == AC3_CHMODE_MONO) { s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB; } else if(s->output_mode == AC3_CHMODE_STEREO) { |