From 6b22e28f4c857b2d9c045001add083343f506d84 Mon Sep 17 00:00:00 2001 From: Lynne Date: Thu, 15 Aug 2019 11:13:35 +0100 Subject: [PATCH] opusdsp: adjust and optimize C function to match assembly The C and asm versions behaved differently _outside_ of the codec. The C version returned pre-multiplied 'state' for the next execution to use right away, while the assembly version outputted non-multiplied 'state' for the next execution to multiply to save instructions. Since the initial state when initialized or seeking is always 0, and since C and asm versions were never mixed, there was no issue. However, comparing outputs directly in checkasm doesn't work without dividing the initial state by CELT_EMPH_COEFF and multiplying the returned state by CELT_EMPH_COEFF for the assembly function. Since its actually faster to do this in C as well, copy the behavior the asm versions use. As a reminder, the initial state 0 is divided by CELT_EMPH_COEFF on seek and init (just in case in the future this is changed, its technically more correct to init with CELT_EMPH_COEFF than 0, however when seeking this will result in more audiable pops, unlike with 0 where the output gets in sync over a few samples). --- libavcodec/opus_celt.c | 6 +++++- libavcodec/opusdsp.c | 11 +++-------- 2 files changed, 8 insertions(+), 9 deletions(-) diff --git a/libavcodec/opus_celt.c b/libavcodec/opus_celt.c index 4655172b09..9dbeff1927 100644 --- a/libavcodec/opus_celt.c +++ b/libavcodec/opus_celt.c @@ -507,7 +507,11 @@ void ff_celt_flush(CeltFrame *f) memset(block->pf_gains_old, 0, sizeof(block->pf_gains_old)); memset(block->pf_gains_new, 0, sizeof(block->pf_gains_new)); - block->emph_coeff = 0.0; + /* libopus uses CELT_EMPH_COEFF on init, but 0 is better since there's + * a lesser discontinuity when seeking. + * The deemphasis functions differ from libopus in that they require + * an initial state divided by the coefficient. */ + block->emph_coeff = 0.0f / CELT_EMPH_COEFF; } f->seed = 0; diff --git a/libavcodec/opusdsp.c b/libavcodec/opusdsp.c index 0e179c98c9..08df87ffbe 100644 --- a/libavcodec/opusdsp.c +++ b/libavcodec/opusdsp.c @@ -43,15 +43,10 @@ static void postfilter_c(float *data, int period, float *gains, int len) static float deemphasis_c(float *y, float *x, float coeff, int len) { - float state = coeff; + for (int i = 0; i < len; i++) + coeff = y[i] = x[i] + coeff*CELT_EMPH_COEFF; - for (int i = 0; i < len; i++) { - const float tmp = x[i] + state; - state = tmp * CELT_EMPH_COEFF; - y[i] = tmp; - } - - return state; + return coeff; } av_cold void ff_opus_dsp_init(OpusDSP *ctx)