From e275318cecee53cf8ce13e4ab41df91c8c7fdcd4 Mon Sep 17 00:00:00 2001 From: John Stebbins Date: Mon, 13 Jan 2014 17:04:30 +0000 Subject: [PATCH] ac3dec: Allow asymmetric application of DRC when drc_scale > 1 Amplification of quiet sounds is enhanced. Inspired by gbooker's A52Decoder. --- libavcodec/ac3dec.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c index 87638e7..0416dbc 100644 --- a/libavcodec/ac3dec.c +++ b/libavcodec/ac3dec.c @@ -772,8 +772,13 @@ static int decode_audio_block(AC3DecodeContext *s, int blk) i = !s->channel_mode; do { if (get_bits1(gbc)) { - s->dynamic_range[i] = powf(dynamic_range_tab[get_bits(gbc, 8)], - s->drc_scale); + /* Allow asymmetric application of DRC when drc_scale > 1. + Amplification of quiet sounds is enhanced */ + float range = dynamic_range_tab[get_bits(gbc, 8)]; + if (range > 1.0 || s->drc_scale <= 1.0) + s->dynamic_range[i] = powf(range, s->drc_scale); + else + s->dynamic_range[i] = range; } else if (blk == 0) { s->dynamic_range[i] = 1.0f; } @@ -1487,7 +1492,7 @@ static av_cold int ac3_decode_end(AVCodecContext *avctx) #define OFFSET(x) offsetof(AC3DecodeContext, x) #define PAR (AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_AUDIO_PARAM) static const AVOption options[] = { - { "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 1.0, PAR }, + { "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 6.0, PAR }, { NULL}, }; -- 1.8.3.4 (Apple Git-47)