Consider per-channel energy bits in surround_rate_allocation()
This should also avoid cases where stereo streams receive fewer
bits than mono streams.
diff --git a/src/opus_multistream_encoder.c b/src/opus_multistream_encoder.c
index 645dfa1..ff1393a 100644
--- a/src/opus_multistream_encoder.c
+++ b/src/opus_multistream_encoder.c
@@ -685,41 +685,50 @@
int lfe_offset;
int coupled_ratio; /* Q8 */
int lfe_ratio; /* Q8 */
+ int nb_lfe;
+ int nb_uncoupled;
+ int nb_coupled;
+ int nb_normal;
+ opus_int32 channel_offset;
+ opus_int32 bitrate;
+ int total;
- if (st->bitrate_bps > st->layout.nb_channels*40000)
- stream_offset = 20000;
- else
- stream_offset = st->bitrate_bps/st->layout.nb_channels/2;
- stream_offset += 60*(Fs/frame_size-50);
- /* We start by giving each stream (coupled or uncoupled) the same bitrate.
+ nb_lfe = (st->lfe_stream!=-1);
+ nb_coupled = st->layout.nb_coupled_streams;
+ nb_uncoupled = st->layout.nb_streams-nb_coupled-nb_lfe;
+ nb_normal = 2*nb_coupled + nb_uncoupled;
+
+ /* Give each non-LFE channel enough bits per channel for coding band energy. */
+ channel_offset = 40*IMAX(50, Fs/frame_size);
+
+ if (st->bitrate_bps==OPUS_AUTO)
+ {
+ bitrate = nb_normal*(channel_offset + Fs + 10000) + 8000*nb_lfe;
+ } else if (st->bitrate_bps==OPUS_BITRATE_MAX)
+ {
+ bitrate = nb_normal*300000 + nb_lfe*128000;
+ } else {
+ bitrate = st->bitrate_bps;
+ }
+
+ /* Give LFE some basic stream_channel allocation but never exceed 1/20 of the
+ total rate for the non-energy part to avoid problems at really low rate. */
+ lfe_offset = IMIN(bitrate/20, 3000) + 15*IMAX(50, Fs/frame_size);
+
+ /* We give each stream (coupled or uncoupled) a starting bitrate.
This models the main saving of coupled channels over uncoupled. */
- /* The LFE stream is an exception to the above and gets fewer bits. */
- lfe_offset = 3500 + 60*(Fs/frame_size-50);
- /* Coupled streams get twice the mono rate after the first 20 kb/s. */
+ stream_offset = (bitrate - channel_offset*nb_normal - lfe_offset*nb_lfe)/nb_normal/2;
+ stream_offset = IMAX(0, IMIN(20000, stream_offset));
+
+ /* Coupled streams get twice the mono rate after the offset is allocated. */
coupled_ratio = 512;
/* Should depend on the bitrate, for now we assume LFE gets 1/8 the bits of mono */
lfe_ratio = 32;
- /* Compute bitrate allocation between streams */
- if (st->bitrate_bps==OPUS_AUTO)
- {
- channel_rate = Fs+60*Fs/frame_size;
- } else if (st->bitrate_bps==OPUS_BITRATE_MAX)
- {
- channel_rate = 300000;
- } else {
- int nb_lfe;
- int nb_uncoupled;
- int nb_coupled;
- int total;
- nb_lfe = (st->lfe_stream!=-1);
- nb_coupled = st->layout.nb_coupled_streams;
- nb_uncoupled = st->layout.nb_streams-nb_coupled-nb_lfe;
- total = (nb_uncoupled<<8) /* mono */
- + coupled_ratio*nb_coupled /* stereo */
- + nb_lfe*lfe_ratio;
- channel_rate = 256*(opus_int64)(st->bitrate_bps-lfe_offset*nb_lfe-stream_offset*(nb_coupled+nb_uncoupled))/total;
- }
+ total = (nb_uncoupled<<8) /* mono */
+ + coupled_ratio*nb_coupled /* stereo */
+ + nb_lfe*lfe_ratio;
+ channel_rate = 256*(opus_int64)(bitrate - lfe_offset*nb_lfe - stream_offset*(nb_coupled+nb_uncoupled) - channel_offset*nb_normal)/total;
#ifndef FIXED_POINT
if (st->variable_duration==OPUS_FRAMESIZE_VARIABLE && frame_size != Fs/50)
{
@@ -732,11 +741,11 @@
for (i=0;i<st->layout.nb_streams;i++)
{
if (i<st->layout.nb_coupled_streams)
- rate[i] = stream_offset+(channel_rate*coupled_ratio>>8);
+ rate[i] = 2*channel_offset + IMAX(0, stream_offset+(channel_rate*coupled_ratio>>8));
else if (i!=st->lfe_stream)
- rate[i] = stream_offset+channel_rate;
+ rate[i] = channel_offset + IMAX(0, stream_offset + channel_rate);
else
- rate[i] = lfe_offset+(channel_rate*lfe_ratio>>8);
+ rate[i] = IMAX(0, lfe_offset+(channel_rate*lfe_ratio>>8));
}
}