commit 8bbdd20a293eab2cfac9f332613ead02a4e3c0c2
Author: Claudio Freire <klaussfreire@gmail.com>
Date:   Sun May 12 09:38:40 2013 +0200

    aacenc: Fix erasure of surround channels
    
    This was due to a miscomputation of s->cur_channel, which led to
    psy-based encoders using the psy coefficients for the wrong channel.
    
    Signed-off-by: Martin Storsjö <martin@martin.st>

diff --git a/libavcodec/aacenc.c b/libavcodec/aacenc.c
index 60eca59..b2ad47b 100644
--- a/libavcodec/aacenc.c
+++ b/libavcodec/aacenc.c
@@ -597,7 +597,7 @@ static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
                 coeffs[ch] = cpe->ch[ch].coeffs;
             s->psy.model->analyze(&s->psy, start_ch, coeffs, wi);
             for (ch = 0; ch < chans; ch++) {
-                s->cur_channel = start_ch * 2 + ch;
+                s->cur_channel = start_ch + ch;
                 s->coder->search_for_quantizers(avctx, s, &cpe->ch[ch], s->lambda);
             }
             cpe->common_window = 0;
@@ -613,7 +613,7 @@ static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
                     }
                 }
             }
-            s->cur_channel = start_ch * 2;
+            s->cur_channel = start_ch;
             if (s->options.stereo_mode && cpe->common_window) {
                 if (s->options.stereo_mode > 0) {
                     IndividualChannelStream *ics = &cpe->ch[0].ics;

commit f4d0a63b5b5c682c18df3bba730f97a9067408ba
Author: Claudio Freire <klaussfreire@gmail.com>
Date:   Sat May 4 18:36:37 2013 -0300

    aacenc: Fix target bitrate for twoloop quantiser search
    
    This fixes a case where multichannel bitrate isn't accurately
    targetted by psy model alone, never achieving the target bitrate.
    
    Signed-off-by: Martin Storsjö <martin@martin.st>

diff --git a/libavcodec/aaccoder.c b/libavcodec/aaccoder.c
index d65d8d9..35b98a9 100644
--- a/libavcodec/aaccoder.c
+++ b/libavcodec/aaccoder.c
@@ -710,7 +710,7 @@ static void search_for_quantizers_twoloop(AVCodecContext *avctx,
                                           const float lambda)
 {
     int start = 0, i, w, w2, g;
-    int destbits = avctx->bit_rate * 1024.0 / avctx->sample_rate / avctx->channels;
+    int destbits = avctx->bit_rate * 1024.0 / avctx->sample_rate / avctx->channels * (lambda / 120.f);
     float dists[128] = { 0 }, uplims[128];
     float maxvals[128];
     int fflag, minscaler;

commit 7c71ada4cad3c6aab5fa24155c379465c41cfd76
Author: Claudio Freire <klaussfreire@gmail.com>
Date:   Sat May 4 18:35:49 2013 -0300

    aacenc: Fix a rounding bug in aacpsy channel bitrate computation
    
    Signed-off-by: Martin Storsjö <martin@martin.st>

diff --git a/libavcodec/aacpsy.c b/libavcodec/aacpsy.c
index 6f1ac05..66cf6d5 100644
--- a/libavcodec/aacpsy.c
+++ b/libavcodec/aacpsy.c
@@ -312,7 +312,7 @@ static av_cold int psy_3gpp_init(FFPsyContext *ctx) {
         AacPsyCoeffs *coeffs = pctx->psy_coef[j];
         const uint8_t *band_sizes = ctx->bands[j];
         float line_to_frequency = ctx->avctx->sample_rate / (j ? 256.f : 2048.0f);
-        float avg_chan_bits = chan_bitrate / ctx->avctx->sample_rate * (j ? 128.0f : 1024.0f);
+        float avg_chan_bits = chan_bitrate * (j ? 128.0f : 1024.0f) / ctx->avctx->sample_rate;
         /* reference encoder uses 2.4% here instead of 60% like the spec says */
         float bark_pe = 0.024f * PSY_3GPP_BITS_TO_PE(avg_chan_bits) / num_bark;
         float en_spread_low = j ? PSY_3GPP_EN_SPREAD_LOW_S : PSY_3GPP_EN_SPREAD_LOW_L;