Better handling of centre for surround masking, bitrate tuning
Centre channel now contributes sqrt(.5) to both channels
Reduces the stream offset at low bitrate
diff --git a/src/opus_multistream_encoder.c b/src/opus_multistream_encoder.c
index eadc11d..3efab53 100644
--- a/src/opus_multistream_encoder.c
+++ b/src/opus_multistream_encoder.c
@@ -37,6 +37,7 @@
#include "float_cast.h"
#include "os_support.h"
#include "analysis.h"
+#include "mathops.h"
typedef struct {
int nb_streams;
@@ -372,9 +373,12 @@
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;
+ else
+ stream_offset = st->bitrate_bps/st->layout.nb_channels/2;
/* We start by giving each stream (coupled or uncoupled) the same bitrate.
This models the main saving of coupled channels over uncoupled. */
- stream_offset = 20000;
/* The LFE stream is an exception to the above and gets fewer bits. */
lfe_offset = 3500;
/* Coupled streams get twice the mono rate after the first 20 kb/s. */
@@ -524,8 +528,16 @@
, &analysis_info
#endif
);
+ /* Combines the left and right mask into a centre mask. We
+ use an approximation for the log of the sum of the energies. */
for(i=0;i<21;i++)
- bandLogE_mono[i] = MAX16(bandLogE[i], bandLogE[21+i]);
+ {
+ opus_val16 diff;
+ diff = ABS16(SUB16(bandLogE[i], bandLogE[21+i]));
+ diff = diff + HALF16(diff);
+ diff = SHR32(HALF32(celt_exp2(-diff)), 16-DB_SHIFT);
+ bandLogE_mono[i] = MAX16(bandLogE[i], bandLogE[21+i]) + diff;
+ }
}
if (max_data_bytes < 4*st->layout.nb_streams-1)
@@ -696,7 +708,7 @@
for (c=0;c<channels;c++)
{
- if (pos[c]==1||pos[c]==2)
+ if (pos[c]==1)
{
for (i=0;i<frame_size;i++)
#if defined(FIXED_POINT)
@@ -704,8 +716,7 @@
#else
dst[2*i] += float_src[i*channels+c];
#endif
- }
- if (pos[c]==2||pos[c]==3)
+ } else if (pos[c]==3)
{
for (i=0;i<frame_size;i++)
#if defined(FIXED_POINT)
@@ -713,6 +724,18 @@
#else
dst[2*i+1] += float_src[i*channels+c];
#endif
+ } else if (pos[c]==2)
+ {
+ for (i=0;i<frame_size;i++)
+ {
+#if defined(FIXED_POINT)
+ dst[2*i] += SHR32(MULT16_16(QCONST16(.70711f,15), FLOAT2INT16(float_src[i*channels+c])),3+15);
+ dst[2*i+1] += SHR32(MULT16_16(QCONST16(.70711f,15), FLOAT2INT16(float_src[i*channels+c])),3+15);
+#else
+ dst[2*i] += .707*float_src[i*channels+c];
+ dst[2*i+1] += .707*float_src[i*channels+c];
+#endif
+ }
}
}
}
@@ -757,7 +780,7 @@
for (c=0;c<channels;c++)
{
- if (pos[c]==1||pos[c]==2)
+ if (pos[c]==1)
{
for (i=0;i<frame_size;i++)
#if defined(FIXED_POINT)
@@ -765,8 +788,7 @@
#else
dst[2*i] += (1/32768.f)*short_src[i*channels+c];
#endif
- }
- if (pos[c]==2||pos[c]==3)
+ } else if (pos[c]==3)
{
for (i=0;i<frame_size;i++)
#if defined(FIXED_POINT)
@@ -774,6 +796,18 @@
#else
dst[2*i+1] += (1/32768.f)*short_src[i*channels+c];
#endif
+ } else if (pos[c]==2)
+ {
+ for (i=0;i<frame_size;i++)
+ {
+#if defined(FIXED_POINT)
+ dst[2*i] += SHR32(MULT16_16(QCONST16(.70711f,15), short_src[i*channels+c]),3+15);
+ dst[2*i+1] += SHR32(MULT16_16(QCONST16(.70711f,15), short_src[i*channels+c]),3+15);
+#else
+ dst[2*i] += (.707f/32768.f)*short_src[i*channels+c];
+ dst[2*i+1] += (.707f/32768.f)*short_src[i*channels+c];
+#endif
+ }
}
}
}