From 1ac3a5630af4e5fb01d5b8d896c377a5e736cc4c Mon Sep 17 00:00:00 2001
From: Michael Graczyk <mgraczyk@google.com>
Date: Mon, 4 Apr 2016 19:31:04 -0700
Subject: [PATCH] Add static bitrate allocation and force CELT-only for
ambisonics encoding
Signed-off-by: Jean-Marc Valin <jmvalin@jmvalin.ca>
---
src/opus_multistream_encoder.c | 103 +++++++++++++++++++++++++++++----
1 file changed, 93 insertions(+), 10 deletions(-)
diff --git a/src/opus_multistream_encoder.c b/src/opus_multistream_encoder.c
index f08789edb..a1cd0f5ce 100644
--- a/src/opus_multistream_encoder.c
+++ b/src/opus_multistream_encoder.c
@@ -512,7 +512,8 @@ int opus_multistream_surround_encoder_init(
int application
)
{
- int mapping_type;
+ MappingType mapping_type;
+
if ((channels>255) || (channels<1))
return OPUS_BAD_ARG;
st->lfe_stream = -1;
@@ -657,24 +658,19 @@ OpusMSEncoder *opus_multistream_surround_encoder_create(
return st;
}
-static opus_int32 surround_rate_allocation(
+static void surround_rate_allocation(
OpusMSEncoder *st,
opus_int32 *rate,
- int frame_size
+ int frame_size,
+ opus_int32 Fs
)
{
int i;
opus_int32 channel_rate;
- opus_int32 Fs;
- char *ptr;
int stream_offset;
int lfe_offset;
int coupled_ratio; /* Q8 */
int lfe_ratio; /* Q8 */
- opus_int32 rate_sum=0;
-
- ptr = (char*)st + align(sizeof(OpusMSEncoder));
- opus_encoder_ctl((OpusEncoder*)ptr, OPUS_GET_SAMPLE_RATE(&Fs));
if (st->bitrate_bps > st->layout.nb_channels*40000)
stream_offset = 20000;
@@ -727,6 +723,88 @@ static opus_int32 surround_rate_allocation(
rate[i] = stream_offset+channel_rate;
else
rate[i] = lfe_offset+(channel_rate*lfe_ratio>>8);
+ }
+}
+
+#ifdef ENABLE_EXPERIMENTAL_AMBISONICS
+static void ambisonics_rate_allocation(
+ OpusMSEncoder *st,
+ opus_int32 *rate,
+ int frame_size,
+ opus_int32 Fs
+ )
+{
+ int i;
+ int non_mono_rate;
+ int total_rate;
+
+ /* The mono channel gets (rate_ratio_num / rate_ratio_den) times as many bits
+ * as all other channels */
+ const int rate_ratio_num = 4;
+ const int rate_ratio_den = 3;
+ const int num_channels = st->layout.nb_streams;
+
+ if (st->bitrate_bps==OPUS_AUTO)
+ {
+ total_rate = num_channels * (20000 + st->layout.nb_streams*(Fs+60*Fs/frame_size));
+ } else if (st->bitrate_bps==OPUS_BITRATE_MAX)
+ {
+ total_rate = num_channels * 320000;
+ } else {
+ total_rate = st->bitrate_bps;
+ }
+
+ /* Let y be the non-mono rate and let p, q be integers such that the mono
+ * channel rate is (p/q) * y.
+ * Also let T be the total bitrate to allocate. Then
+ * (n - 1) y + (p/q) y = T
+ * y = (T q) / (qn - q + p)
+ */
+ non_mono_rate =
+ total_rate * rate_ratio_den
+ / (rate_ratio_den*num_channels + rate_ratio_num - rate_ratio_den);
+
+#ifndef FIXED_POINT
+ if (st->variable_duration==OPUS_FRAMESIZE_VARIABLE && frame_size != Fs/50)
+ {
+ opus_int32 bonus = 60*(Fs/frame_size-50);
+ non_mono_rate += bonus;
+ }
+#endif
+
+ rate[0] = total_rate - (num_channels - 1) * non_mono_rate;
+ for (i=1;i<st->layout.nb_streams;i++)
+ {
+ rate[i] = non_mono_rate;
+ }
+}
+#endif /* ENABLE_EXPERIMENTAL_AMBISONICS */
+
+static opus_int32 rate_allocation(
+ OpusMSEncoder *st,
+ opus_int32 *rate,
+ int frame_size
+ )
+{
+ int i;
+ opus_int32 rate_sum=0;
+ opus_int32 Fs;
+ char *ptr;
+
+ ptr = (char*)st + align(sizeof(OpusMSEncoder));
+ opus_encoder_ctl((OpusEncoder*)ptr, OPUS_GET_SAMPLE_RATE(&Fs));
+
+#ifdef ENABLE_EXPERIMENTAL_AMBISONICS
+ if (st->mapping_type == MAPPING_TYPE_AMBISONICS) {
+ ambisonics_rate_allocation(st, rate, frame_size, Fs);
+ } else
+#endif
+ {
+ surround_rate_allocation(st, rate, frame_size, Fs);
+ }
+
+ for (i=0;i<st->layout.nb_streams;i++)
+ {
rate[i] = IMAX(rate[i], 500);
rate_sum += rate[i];
}
@@ -829,7 +907,7 @@ static int opus_multistream_encode_native
}
/* Compute bitrate allocation between streams (this could be a lot better) */
- rate_sum = surround_rate_allocation(st, bitrates, frame_size);
+ rate_sum = rate_allocation(st, bitrates, frame_size);
if (!vbr)
{
@@ -873,6 +951,11 @@ static int opus_multistream_encode_native
opus_encoder_ctl(enc, OPUS_SET_FORCE_CHANNELS(2));
}
}
+#ifdef ENABLE_EXPERIMENTAL_AMBISONICS
+ else if (st->mapping_type == MAPPING_TYPE_AMBISONICS) {
+ opus_encoder_ctl(enc, OPUS_SET_FORCE_MODE(MODE_CELT_ONLY));
+ }
+#endif
}
ptr = (char*)st + align(sizeof(OpusMSEncoder));
--
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