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Consider per-channel energy bits in surround_rate_allocation()

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This should also avoid cases where stereo streams receive fewer
bits than mono streams.
This commit is contained in:
Jean-Marc Valin 2016-09-19 17:18:58 -04:00
parent a3fadcb9f4
commit 8ac5d89918
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GPG key ID: 5E5DD9A36F9189C8
1 changed files with 41 additions and 32 deletions
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73
src/opus_multistream_encoder.c
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@ -685,41 +685,50 @@ static void surround_rate_allocation(
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 @@ static void surround_rate_allocation(
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));
}
}