From c2a6ac4e341f7224ef8e30ad4e1eee79a516e069 Mon Sep 17 00:00:00 2001 From: Marcin Gorzel Date: Thu, 30 Aug 2018 13:15:21 +0100 Subject: Apply equal bit allocation to ambisonic channels Fixes issue #95 on GitHub. Signed-off-by: Felicia Lim --- src/opus_multistream_encoder.c | 57 +++++------------------------------------- 1 file changed, 6 insertions(+), 51 deletions(-) diff --git a/src/opus_multistream_encoder.c b/src/opus_multistream_encoder.c index 6cc1f432..9cb9bf34 100644 --- a/src/opus_multistream_encoder.c +++ b/src/opus_multistream_encoder.c @@ -742,20 +742,9 @@ static void ambisonics_rate_allocation( { int i; opus_int32 total_rate; - opus_int32 directional_rate; - opus_int32 nondirectional_rate; - opus_int32 leftover_bits; - - /* Each nondirectional channel gets (rate_ratio_num / rate_ratio_den) times - * as many bits as all other ambisonics channels. - */ - const int rate_ratio_num = 4; - const int rate_ratio_den = 3; + opus_int32 per_stream_rate; + const int nb_channels = st->layout.nb_streams + st->layout.nb_coupled_streams; - /* The omnidirectional ambisonics and non-diegetic stereo channels */ - const int nb_nondirectional_channels = st->layout.nb_coupled_streams * 2 + 1; - /* The remaining ambisonics channels */ - const int nb_directional_channels = nb_channels - nb_nondirectional_channels; if (st->bitrate_bps==OPUS_AUTO) { @@ -769,46 +758,12 @@ static void ambisonics_rate_allocation( total_rate = st->bitrate_bps; } - /* Let y be the directional rate, m be the num of nondirectional channels - * m = (s + 1) - * and let p, q be integers such that the nondirectional rate is - * m_rate = (p / q) * y - * Also let T be the total bitrate to allocate. Then - * T = (n - m) * y + m * m_rate - * Solving for y, - * y = (q * T) / (m * (p - q) + n * q) - */ - directional_rate = - total_rate * rate_ratio_den - / (nb_nondirectional_channels * (rate_ratio_num - rate_ratio_den) - + nb_channels * rate_ratio_den); - - /* Calculate the nondirectional rate. - * m_rate = y * (p / q) - */ - nondirectional_rate = directional_rate * rate_ratio_num / rate_ratio_den; - - /* Calculate the leftover from truncation error. - * leftover = T - y * (n - m) - m_rate * m - * Place leftover bits in omnidirectional channel. - */ - leftover_bits = total_rate - - directional_rate * nb_directional_channels - - nondirectional_rate * nb_nondirectional_channels; - - /* Calculate rates for each channel */ + /* Allocate equal number of bits to Ambisonic (uncoupled) and non-diegetic + * (coupled) streams */ + per_stream_rate = total_rate / st->layout.nb_streams; for (i = 0; i < st->layout.nb_streams; i++) { - if (i < st->layout.nb_coupled_streams) - { - rate[i] = nondirectional_rate * 2; - } else if (i == st->layout.nb_coupled_streams) - { - rate[i] = nondirectional_rate + leftover_bits; - } else - { - rate[i] = directional_rate; - } + rate[i] = per_stream_rate; } } -- cgit v1.2.1