[FFmpeg-cvslog] aaccoder: fix M/S coding

[Rostislav Pehlivanov]

ffmpeg | branch: master | Rostislav Pehlivanov <atomnuker at gmail.com> | Thu Jul  2 19:13:02 2015 +0100| [57848ef3c6a135caeb1f8034cadc157a38947009] | committer: Michael Niedermayer

aaccoder: fix M/S coding

There were some mistakes in the code for M/S stereo, this commit fixes them.
The start variable was not being reset for every window and every access to
the coefficients was incorrect as well. This fixes that by properly
addressing the coefficients using both windows and setting the start on every window to zero.

Reviewed-by: Claudio Freire <klaussfreire at gmail.com>
Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=57848ef3c6a135caeb1f8034cadc157a38947009
---

 libavcodec/aaccoder.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/libavcodec/aaccoder.c b/libavcodec/aaccoder.c
index cd996b2..aaf70d5 100644
--- a/libavcodec/aaccoder.c
+++ b/libavcodec/aaccoder.c
@@ -1166,6 +1166,7 @@ static void search_for_ms(AACEncContext *s, ChannelElement *cpe,
     if (!cpe->common_window)
         return;
     for (w = 0; w < sce0->ics.num_windows; w += sce0->ics.group_len[w]) {
+        start = 0;
         for (g = 0;  g < sce0->ics.num_swb; g++) {
             if (!cpe->ch[0].zeroes[w*16+g] && !cpe->ch[1].zeroes[w*16+g]) {
                 float dist1 = 0.0f, dist2 = 0.0f;
@@ -1175,22 +1176,22 @@ static void search_for_ms(AACEncContext *s, ChannelElement *cpe,
                     float minthr = FFMIN(band0->threshold, band1->threshold);
                     float maxthr = FFMAX(band0->threshold, band1->threshold);
                     for (i = 0; i < sce0->ics.swb_sizes[g]; i++) {
-                        M[i] = (sce0->pcoeffs[start+w2*128+i]
-                              + sce1->pcoeffs[start+w2*128+i]) * 0.5;
+                        M[i] = (sce0->pcoeffs[start+(w+w2)*128+i]
+                              + sce1->pcoeffs[start+(w+w2)*128+i]) * 0.5;
                         S[i] =  M[i]
-                              - sce1->pcoeffs[start+w2*128+i];
+                              - sce1->pcoeffs[start+(w+w2)*128+i];
                     }
-                    abs_pow34_v(L34, sce0->coeffs+start+w2*128, sce0->ics.swb_sizes[g]);
-                    abs_pow34_v(R34, sce1->coeffs+start+w2*128, sce0->ics.swb_sizes[g]);
+                    abs_pow34_v(L34, sce0->coeffs+start+(w+w2)*128, sce0->ics.swb_sizes[g]);
+                    abs_pow34_v(R34, sce1->coeffs+start+(w+w2)*128, sce0->ics.swb_sizes[g]);
                     abs_pow34_v(M34, M,                         sce0->ics.swb_sizes[g]);
                     abs_pow34_v(S34, S,                         sce0->ics.swb_sizes[g]);
-                    dist1 += quantize_band_cost(s, sce0->coeffs + start + w2*128,
+                    dist1 += quantize_band_cost(s, sce0->coeffs + start + (w+w2)*128,
                                                 L34,
                                                 sce0->ics.swb_sizes[g],
                                                 sce0->sf_idx[(w+w2)*16+g],
                                                 sce0->band_type[(w+w2)*16+g],
                                                 lambda / band0->threshold, INFINITY, NULL);
-                    dist1 += quantize_band_cost(s, sce1->coeffs + start + w2*128,
+                    dist1 += quantize_band_cost(s, sce1->coeffs + start + (w+w2)*128,
                                                 R34,
                                                 sce1->ics.swb_sizes[g],
                                                 sce1->sf_idx[(w+w2)*16+g],