diff options
author | Jean-Marc Valin <jmvalin@jmvalin.ca> | 2016-09-20 00:18:58 +0300 |
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committer | Jean-Marc Valin <jmvalin@jmvalin.ca> | 2016-09-20 05:10:09 +0300 |
commit | 8ac5d8991888704e8f75401d1c36ab94ee597ea8 (patch) | |
tree | 8ab98a46b0d999454076159ec05162a21bcebdcd /src/opus_multistream_encoder.c | |
parent | a3fadcb9f48c2504abe9d375adb2837b2c2cd4e3 (diff) |
Consider per-channel energy bits in surround_rate_allocation()
This should also avoid cases where stereo streams receive fewer
bits than mono streams.
Diffstat (limited to 'src/opus_multistream_encoder.c')
-rw-r--r-- | src/opus_multistream_encoder.c | 71 |
1 files changed, 40 insertions, 31 deletions
diff --git a/src/opus_multistream_encoder.c b/src/opus_multistream_encoder.c index 645dfa15..ff1393a2 100644 --- a/src/opus_multistream_encoder.c +++ b/src/opus_multistream_encoder.c @@ -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; + + 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 > 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. - 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. */ - 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; + bitrate = nb_normal*(channel_offset + Fs + 10000) + 8000*nb_lfe; } else if (st->bitrate_bps==OPUS_BITRATE_MAX) { - channel_rate = 300000; + bitrate = nb_normal*300000 + nb_lfe*128000; } 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; + 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. */ + 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; + + 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)); } } |