| Message ID | 1473074325-20959-3-git-send-email-pburt0@gmail.com |
|---|---|
| State | Accepted |
| Commit | 38445d58f1a1cdc69bb11309e07aa99360bf466b |
| Headers | show |
On Mon, Sep 05, 2016 at 06:18:42AM -0500, Burt P wrote: > Signed-off-by: Burt P <pburt0@gmail.com> > --- > libavfilter/af_hdcd.c | 9 ++++----- > 1 file changed, 4 insertions(+), 5 deletions(-) > > diff --git a/libavfilter/af_hdcd.c b/libavfilter/af_hdcd.c > index cde2340..c8bda82 100644 > --- a/libavfilter/af_hdcd.c > +++ b/libavfilter/af_hdcd.c > @@ -1316,11 +1316,10 @@ static void hdcd_analyze_prepare(hdcd_state *state, int32_t *samples, int count, > /** encode a value in the given sample by adjusting the amplitude */ > static int32_t hdcd_analyze_gen(int32_t sample, unsigned int v, unsigned int maxv) > { > - float sflt = sample, vv = v; > - vv /= maxv; > - if (vv > 1.0) vv = 1.0; > - sflt *= 1.0 + (vv * 18); > - return (int32_t)sflt; > + static const int r = 18, m = 1024; > + int64_t s64 = sample; > + v = m + (v * r * m / maxv); maxv is always a constant (for each call) and division is slow, maybe you want to replace it by multiplication by its inverse and adjust the /m later (that is fast as m is a constant power of 2 in unsigned context) [...[
applied as is for now. Thanks for the comment. I will look into a faster way of doing it. I only needed to change from the float version because it was giving different results for i686 than for amd64. I don't know why, exactly, but I do know that this version gives bit-perfect results everywhere I've tried it.
diff --git a/libavfilter/af_hdcd.c b/libavfilter/af_hdcd.c index cde2340..c8bda82 100644 --- a/libavfilter/af_hdcd.c +++ b/libavfilter/af_hdcd.c @@ -1316,11 +1316,10 @@ static void hdcd_analyze_prepare(hdcd_state *state, int32_t *samples, int count, /** encode a value in the given sample by adjusting the amplitude */ static int32_t hdcd_analyze_gen(int32_t sample, unsigned int v, unsigned int maxv) { - float sflt = sample, vv = v; - vv /= maxv; - if (vv > 1.0) vv = 1.0; - sflt *= 1.0 + (vv * 18); - return (int32_t)sflt; + static const int r = 18, m = 1024; + int64_t s64 = sample; + v = m + (v * r * m / maxv); + return (int32_t)(s64 * v / m); } /** behaves like hdcd_envelope(), but encodes processing information in
Signed-off-by: Burt P <pburt0@gmail.com> --- libavfilter/af_hdcd.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)