[FFmpeg-devel] [PATCH v2 7/8] aacenc: add support for coding of IS spectral coefficients

Rostislav Pehlivanov atomnuker at gmail.com
Thu Jul 2 20:13:06 CEST 2015


This commit adds support for the coding of intensity stereo spectral coefficients. It also fixes the Mid/Side coding of band_types higher than RESERVED_BT (M/S must not be applied to their spectral coefficients, but marking M/S as present in encode_ms_info() is okay). Much of the changes here were taken from the decoder and inverted. This commit does not change the functionality of the decoder as the previous patch in this series zeroes ms_mask and is_mask.

Reviewed-by: Claudio Freire <klaussfreire at gmail.com>
---
 libavcodec/aacenc.c | 37 +++++++++++++++++++++++++++----------
 1 file changed, 27 insertions(+), 10 deletions(-)

diff --git a/libavcodec/aacenc.c b/libavcodec/aacenc.c
index f7325d4..3e5ac72 100644
--- a/libavcodec/aacenc.c
+++ b/libavcodec/aacenc.c
@@ -312,19 +312,26 @@ static void encode_ms_info(PutBitContext *pb, ChannelElement *cpe)
 static void adjust_frame_information(ChannelElement *cpe, int chans)
 {
     int i, w, w2, g, ch;
-    int start, maxsfb, cmaxsfb;
+    int maxsfb, cmaxsfb;
+    IndividualChannelStream *ics;
 
-    for (ch = 0; ch < chans; ch++) {
-        IndividualChannelStream *ics = &cpe->ch[ch].ics;
-        start = 0;
-        maxsfb = 0;
-        cpe->ch[ch].pulse.num_pulse = 0;
+    if (cpe->common_window) {
+        ics = &cpe->ch[0].ics;
         for (w = 0; w < ics->num_windows; w += ics->group_len[w]) {
-            for (w2 = 0; w2 < ics->group_len[w]; w2++) {
-                start = (w+w2) * 128;
+            for (w2 =  0; w2 < ics->group_len[w]; w2++) {
+                int start = (w+w2) * 128;
                 for (g = 0; g < ics->num_swb; g++) {
-                    //apply M/S
-                    if (cpe->common_window && !ch && cpe->ms_mask[w*16 + g]) {
+                    //apply Intensity stereo coeffs transformation
+                    if (cpe->is_mask[w*16 + g]) {
+                        int p = -1 + 2 * (cpe->ch[1].band_type[w*16+g] - 14);
+                        float scale = cpe->ch[0].is_ener[w*16+g];
+                        for (i = 0; i < ics->swb_sizes[g]; i++) {
+                            cpe->ch[0].coeffs[start+i] = (cpe->ch[0].pcoeffs[start+i] + p*cpe->ch[1].pcoeffs[start+i]) * scale;
+                            cpe->ch[1].coeffs[start+i] = 0.0f;
+                        }
+                    } else if (cpe->ms_mask[w*16 + g] &&
+                               cpe->ch[0].band_type[w*16 + g] < NOISE_BT &&
+                               cpe->ch[1].band_type[w*16 + g] < NOISE_BT) {
                         for (i = 0; i < ics->swb_sizes[g]; i++) {
                             cpe->ch[0].coeffs[start+i] = (cpe->ch[0].pcoeffs[start+i] + cpe->ch[1].pcoeffs[start+i]) * 0.5f;
                             cpe->ch[1].coeffs[start+i] = cpe->ch[0].coeffs[start+i] - cpe->ch[1].pcoeffs[start+i];
@@ -332,6 +339,16 @@ static void adjust_frame_information(ChannelElement *cpe, int chans)
                     }
                     start += ics->swb_sizes[g];
                 }
+            }
+        }
+    }
+
+    for (ch = 0; ch < chans; ch++) {
+        IndividualChannelStream *ics = &cpe->ch[ch].ics;
+        maxsfb = 0;
+        cpe->ch[ch].pulse.num_pulse = 0;
+        for (w = 0; w < ics->num_windows; w += ics->group_len[w]) {
+            for (w2 =  0; w2 < ics->group_len[w]; w2++) {
                 for (cmaxsfb = ics->num_swb; cmaxsfb > 0 && cpe->ch[ch].zeroes[w*16+cmaxsfb-1]; cmaxsfb--)
                     ;
                 maxsfb = FFMAX(maxsfb, cmaxsfb);
-- 
2.1.4



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