ffmpeg | branch: master | Claudio Freire <klaussfre...@gmail.com> | Sun Jan 10 03:04:21 2016 -0300| [699c2ee560532a5111a944d2653e9a3e484efc34] | committer: Claudio Freire
AAC encoder: encode out-of-phase I/S efficiently Use the ability to invert phase with ms_mask instead of changing the codebook when possible, to avoid having to switch codebooks if some bands are INTENSTY_BT and others are INTENSITY_BT2, since usually a set ms_mask uses less bits that a codebook change. While it may not always be a win (ie: if it causes an ms_mask bitmap to be sent when it wouldn't have been otherwise), it's unlikely since the ms_mask bitmap will almost always be there already for M/S itself. > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=699c2ee560532a5111a944d2653e9a3e484efc34 --- libavcodec/aacenc_is.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/libavcodec/aacenc_is.c b/libavcodec/aacenc_is.c index d77fcb5..405f178 100644 --- a/libavcodec/aacenc_is.c +++ b/libavcodec/aacenc_is.c @@ -99,7 +99,7 @@ void ff_aac_search_for_is(AACEncContext *s, AVCodecContext *avctx, ChannelElemen { SingleChannelElement *sce0 = &cpe->ch[0]; SingleChannelElement *sce1 = &cpe->ch[1]; - int start = 0, count = 0, w, w2, g, i, prev_sf1 = -1; + int start = 0, count = 0, w, w2, g, i, prev_sf1 = -1, prev_bt = -1, prev_is = 0; const float freq_mult = avctx->sample_rate/(1024.0f/sce0->ics.num_windows)/2.0f; uint8_t nextband1[128]; @@ -139,11 +139,18 @@ void ff_aac_search_for_is(AACEncContext *s, AVCodecContext *avctx, ChannelElemen cpe->ch[0].is_ener[w*16+g] = sqrt(ener0 / best->ener01); cpe->ch[1].is_ener[w*16+g] = ener0/ener1; cpe->ch[1].band_type[w*16+g] = (best->phase > 0) ? INTENSITY_BT : INTENSITY_BT2; + if (prev_is && prev_bt != cpe->ch[1].band_type[w*16+g]) { + /** Flip M/S mask and pick the other CB, since it encodes more efficiently */ + cpe->ms_mask[w*16+g] = 1; + cpe->ch[1].band_type[w*16+g] = (best->phase > 0) ? INTENSITY_BT2 : INTENSITY_BT; + } + prev_bt = cpe->ch[1].band_type[w*16+g]; count++; } } if (!sce1->zeroes[w*16+g] && sce1->band_type[w*16+g] < RESERVED_BT) prev_sf1 = sce1->sf_idx[w*16+g]; + prev_is = cpe->is_mask[w*16+g]; start += sce0->ics.swb_sizes[g]; } } _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog
