This decoder-side change, introduced in RFC 8251 (section 9), slightly improves the decoded quality of 16kbps speech in Hybrid Mode.
Differences can be seen/heard in testvector05.bit, testvector06.bit, and testvector12.bit in the RFC 6716/8251 testvectors found here: https://people.xiph.org/~greg/opus_testvectors/ Signed-off-by: Andrew D'Addesio <modchip...@gmail.com> --- libavcodec/opus_celt.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/libavcodec/opus_celt.c b/libavcodec/opus_celt.c index ff56041..2bbb96b 100644 --- a/libavcodec/opus_celt.c +++ b/libavcodec/opus_celt.c @@ -712,10 +712,22 @@ static void celt_decode_bands(CeltFrame *f, OpusRangeCoder *rc) b = av_clip_uintp2(FFMIN(f->remaining2 + 1, f->pulses[i] + curr_balance), 14); } - if (ff_celt_freq_bands[i] - ff_celt_freq_range[i] >= ff_celt_freq_bands[f->start_band] && - (update_lowband || lowband_offset == 0)) + if ((ff_celt_freq_bands[i] - ff_celt_freq_range[i] >= ff_celt_freq_bands[f->start_band] || + i == f->start_band + 1) && (update_lowband || lowband_offset == 0)) lowband_offset = i; + if (i == f->start_band + 1) { + /* Special Hybrid Folding (RFC 8251 section 9). Copy the first band into + the second to ensure the second band never has to use the LCG. */ + int offset = 8 * ff_celt_freq_bands[i]; + int count = 8 * (ff_celt_freq_range[i] - ff_celt_freq_range[i-1]); + + memcpy(&norm[offset], &norm[offset - count], count * sizeof(float)); + + if (f->channels == 2) + memcpy(&norm2[offset], &norm2[offset - count], count * sizeof(float)); + } + /* Get a conservative estimate of the collapse_mask's for the bands we're going to be folding from. */ if (lowband_offset != 0 && (f->spread != CELT_SPREAD_AGGRESSIVE || @@ -728,7 +740,7 @@ static void celt_decode_bands(CeltFrame *f, OpusRangeCoder *rc) foldstart = lowband_offset; while (ff_celt_freq_bands[--foldstart] > effective_lowband); foldend = lowband_offset - 1; - while (ff_celt_freq_bands[++foldend] < effective_lowband + ff_celt_freq_range[i]); + while (++foldend < i && ff_celt_freq_bands[foldend] < effective_lowband + ff_celt_freq_range[i]); cm[0] = cm[1] = 0; for (j = foldstart; j < foldend; j++) { -- 2.15.1.windows.2 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
