diff --git a/libavcodec/aaccoder.c b/libavcodec/aaccoder.c
index 95782fc49e..5bdba46b92 100644
--- a/libavcodec/aaccoder.c
+++ b/libavcodec/aaccoder.c
@@ -52,6 +52,9 @@
  * excessive PNS and little PNS usage. */
 #define NOISE_LAMBDA_NUMERATOR 252.1f
 
+/** Frequency in Hz for lower limit of intensity stereo   **/
+#define INT_STEREO_LOW_LIMIT 6100
+
 /** Total number of usable codebooks **/
 #define CB_TOT 12
 
@@ -1178,6 +1181,104 @@ static void search_for_pns(AACEncContext *s, AVCodecContext *avctx, SingleChanne
     }
 }
 
+static void search_for_is(AACEncContext *s, AVCodecContext *avctx, ChannelElement *cpe,
+                          const float lambda)
+{
+    float IS[128];
+    float *L34  = s->scoefs + 128*0, *R34  = s->scoefs + 128*1;
+    float *I34  = s->scoefs + 128*2;
+    SingleChannelElement *sce0 = &cpe->ch[0];
+    SingleChannelElement *sce1 = &cpe->ch[1];
+    int start = 0, count = 0, i, w, w2, g;
+    const float freq_mult = avctx->sample_rate/(1024.0f/sce0->ics.num_windows)/2.0f;
+
+    for (w = 0; w < 128; w++)
+        if (sce1->band_type[w] >= INTENSITY_BT2)
+            sce1->band_type[w] = 0;
+
+    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 (start*freq_mult > INT_STEREO_LOW_LIMIT*(lambda/170.0f) &&
+                cpe->ch[0].band_type[w*16+g] != NOISE_BT && !cpe->ch[0].zeroes[w*16+g] &&
+                cpe->ch[1].band_type[w*16+g] != NOISE_BT && !cpe->ch[1].zeroes[w*16+g]) {
+                int phase = 0;
+                float ener0 = 0.0f, ener1 = 0.0f, ener01 = 0.0f;
+                float dist1 = 0.0f, dist2 = 0.0f;
+                for (w2 = 0; w2 < sce0->ics.group_len[w]; w2++) {
+                    for (i = 0; i < sce0->ics.swb_sizes[g]; i++) {
+                        float coef0 = sce0->pcoeffs[start+(w+w2)*128+i];
+                        float coef1 = sce1->pcoeffs[start+(w+w2)*128+i];
+                        phase += coef0*coef1 >= 0.0f ? 1 : -1;
+                        ener0 += coef0*coef0;
+                        ener1 += coef1*coef1;
+                        ener01 += (coef0 + coef1)*(coef0 + coef1);
+                    }
+                }
+                if (!phase) { /* Too much phase difference between channels */
+                    start += sce0->ics.swb_sizes[g];
+                    continue;
+                }
+                phase = av_clip(phase, -1, 1);
+                for (w2 = 0; w2 < sce0->ics.group_len[w]; w2++) {
+                    FFPsyBand *band0 = &s->psy.ch[s->cur_channel+0].psy_bands[(w+w2)*16+g];
+                    FFPsyBand *band1 = &s->psy.ch[s->cur_channel+1].psy_bands[(w+w2)*16+g];
+                    int is_band_type, is_sf_idx = FFMAX(1, sce0->sf_idx[(w+w2)*16+g]-4);
+                    float e01_34 = phase*pow(sqrt(ener1/ener0), 3.0/4.0);
+                    float maxval, dist_spec_err = 0.0f;
+                    float minthr = FFMIN(band0->threshold, band1->threshold);
+                    for (i = 0; i < sce0->ics.swb_sizes[g]; i++)
+                        IS[i] = (sce0->pcoeffs[start+(w+w2)*128+i] + phase*sce1->pcoeffs[start+(w+w2)*128+i]) * sqrt(ener0/ener01);
+                    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(I34, IS,                            sce0->ics.swb_sizes[g]);
+                    maxval = find_max_val(1, sce0->ics.swb_sizes[g], I34);
+                    is_band_type = find_min_book(maxval, is_sf_idx);
+                    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 + (w+w2)*128,
+                                                R34,
+                                                sce1->ics.swb_sizes[g],
+                                                sce1->sf_idx[(w+w2)*16+g],
+                                                sce1->band_type[(w+w2)*16+g],
+                                                lambda / band1->threshold, INFINITY, NULL);
+                    dist2 += quantize_band_cost(s, IS,
+                                                I34,
+                                                sce0->ics.swb_sizes[g],
+                                                is_sf_idx,
+                                                is_band_type,
+                                                lambda / minthr, INFINITY, NULL);
+                    for (i = 0; i < sce0->ics.swb_sizes[g]; i++) {
+                        dist_spec_err += (L34[i] - I34[i])*(L34[i] - I34[i]);
+                        dist_spec_err += (R34[i] - I34[i]*e01_34)*(R34[i] - I34[i]*e01_34);
+                    }
+                    dist_spec_err *= lambda / minthr;
+                    dist2 += dist_spec_err;
+                }
+                if (dist2 <= dist1) {
+                    cpe->is_mask[w*16+g] = 1;
+                    cpe->ms_mask[w*16+g] = 0;
+                    cpe->ch[0].is_ener[w*16+g] = sqrt(ener0/ener01);
+                    cpe->ch[1].is_ener[w*16+g] = ener0/ener1;
+                    if (phase)
+                        cpe->ch[1].band_type[w*16+g] = INTENSITY_BT;
+                    else
+                        cpe->ch[1].band_type[w*16+g] = INTENSITY_BT2;
+                    count++;
+                }
+            }
+            start += sce0->ics.swb_sizes[g];
+        }
+    }
+    cpe->is_mode = !!count;
+}
+
 static void search_for_ms(AACEncContext *s, ChannelElement *cpe,
                           const float lambda)
 {
@@ -1191,7 +1292,7 @@ static void search_for_ms(AACEncContext *s, ChannelElement *cpe,
     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]) {
+            if (!cpe->ch[0].zeroes[w*16+g] && !cpe->ch[1].zeroes[w*16+g] && !cpe->is_mask[w*16+g]) {
                 float dist1 = 0.0f, dist2 = 0.0f;
                 for (w2 = 0; w2 < sce0->ics.group_len[w]; w2++) {
                     FFPsyBand *band0 = &s->psy.ch[s->cur_channel+0].psy_bands[(w+w2)*16+g];
@@ -1248,6 +1349,7 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = {
         set_special_band_scalefactors,
         search_for_pns,
         search_for_ms,
+        search_for_is,
     },
     [AAC_CODER_ANMR] = {
         search_for_quantizers_anmr,
@@ -1256,6 +1358,7 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = {
         set_special_band_scalefactors,
         search_for_pns,
         search_for_ms,
+        search_for_is,
     },
     [AAC_CODER_TWOLOOP] = {
         search_for_quantizers_twoloop,
@@ -1264,6 +1367,7 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = {
         set_special_band_scalefactors,
         search_for_pns,
         search_for_ms,
+        search_for_is,
     },
     [AAC_CODER_FAST] = {
         search_for_quantizers_fast,
@@ -1272,5 +1376,6 @@ AACCoefficientsEncoder ff_aac_coders[AAC_CODER_NB] = {
         set_special_band_scalefactors,
         search_for_pns,
         search_for_ms,
+        search_for_is,
     },
 };
diff --git a/libavcodec/aacenc.c b/libavcodec/aacenc.c
index 3e5ac725aa..a4248ff517 100644
--- a/libavcodec/aacenc.c
+++ b/libavcodec/aacenc.c
@@ -550,7 +550,7 @@ static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
     AACEncContext *s = avctx->priv_data;
     float **samples = s->planar_samples, *samples2, *la, *overlap;
     ChannelElement *cpe;
-    int i, ch, w, g, chans, tag, start_ch, ret, ms_mode = 0;
+    int i, ch, w, g, chans, tag, start_ch, ret, ms_mode = 0, is_mode = 0;
     int chan_el_counter[4];
     FFPsyWindowInfo windows[AAC_MAX_CHANNELS];
 
@@ -675,6 +675,10 @@ static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
                     s->coder->search_for_ms(s, cpe, s->lambda);
                 }
             }
+            if (chans > 1 && s->options.intensity_stereo && s->coder->search_for_is) {
+                s->coder->search_for_is(s, avctx, cpe, s->lambda);
+                if (cpe->is_mode) is_mode = 1;
+            }
             if (s->coder->set_special_band_scalefactors)
                 for (ch = 0; ch < chans; ch++)
                     s->coder->set_special_band_scalefactors(s, &cpe->ch[ch]);
@@ -699,7 +703,7 @@ static int aac_encode_frame(AVCodecContext *avctx, AVPacket *avpkt,
             s->psy.bitres.bits = frame_bits / s->channels;
             break;
         }
-        if (ms_mode) {
+        if (is_mode || ms_mode) {
             for (i = 0; i < s->chan_map[0]; i++) {
                 // Must restore coeffs
                 chans = tag == TYPE_CPE ? 2 : 1;
@@ -877,6 +881,9 @@ static const AVOption aacenc_options[] = {
     {"aac_pns", "Perceptual Noise Substitution", offsetof(AACEncContext, options.pns), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, AACENC_FLAGS, "aac_pns"},
         {"disable",  "Disable PNS", 0, AV_OPT_TYPE_CONST, {.i64 =  0 }, INT_MIN, INT_MAX, AACENC_FLAGS, "aac_pns"},
         {"enable",   "Enable PNS (Proof of concept)",  0, AV_OPT_TYPE_CONST, {.i64 =  1 }, INT_MIN, INT_MAX, AACENC_FLAGS, "aac_pns"},
+    {"aac_is", "Intensity stereo coding", offsetof(AACEncContext, options.intensity_stereo), AV_OPT_TYPE_INT, {.i64 = 0}, 0, 1, AACENC_FLAGS, "intensity_stereo"},
+        {"disable", "Disable intensity stereo coding", 0, AV_OPT_TYPE_CONST, {.i64 = 0}, INT_MIN, INT_MAX, AACENC_FLAGS, "intensity_stereo"},
+        {"enable",   "Enable intensity stereo coding", 0, AV_OPT_TYPE_CONST, {.i64 = 1}, INT_MIN, INT_MAX, AACENC_FLAGS, "intensity_stereo"},
     {NULL}
 };
 
diff --git a/libavcodec/aacenc.h b/libavcodec/aacenc.h
index 8ba58174a4..966c70889e 100644
--- a/libavcodec/aacenc.h
+++ b/libavcodec/aacenc.h
@@ -43,6 +43,7 @@ typedef struct AACEncOptions {
     int stereo_mode;
     int aac_coder;
     int pns;
+    int intensity_stereo;
 } AACEncOptions;
 
 struct AACEncContext;
@@ -57,6 +58,7 @@ typedef struct AACCoefficientsEncoder {
     void (*set_special_band_scalefactors)(struct AACEncContext *s, SingleChannelElement *sce);
     void (*search_for_pns)(struct AACEncContext *s, AVCodecContext *avctx, SingleChannelElement *sce, const float lambda);
     void (*search_for_ms)(struct AACEncContext *s, ChannelElement *cpe, const float lambda);
+    void (*search_for_is)(struct AACEncContext *s, AVCodecContext *avctx, ChannelElement *cpe, const float lambda);
 } AACCoefficientsEncoder;
 
 extern AACCoefficientsEncoder ff_aac_coders[];