From acbb2777e28c462d38f774d317e6cd3ad2a0b215 Mon Sep 17 00:00:00 2001
From: Paul B Mahol <onemda@gmail.com>
Date: Tue, 20 Sep 2022 17:07:15 +0200
Subject: [PATCH] avcodec/ac3dec: add downmix support for mono and stereo for
 eac3 7.1

---
 libavcodec/ac3dec.c | 55 ++++++++++++++++++++++++++-------------------
 1 file changed, 32 insertions(+), 23 deletions(-)

diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 5d0add40fe..f628eae33c 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -183,6 +183,33 @@ static av_cold void ac3_tables_init(void)
 #endif
 }
 
+static void ac3_downmix(AVCodecContext *avctx)
+{
+    AC3DecodeContext *s = avctx->priv_data;
+    const AVChannelLayout mono   = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
+    const AVChannelLayout stereo = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
+
+    /* allow downmixing to stereo or mono */
+#if FF_API_OLD_CHANNEL_LAYOUT
+FF_DISABLE_DEPRECATION_WARNINGS
+    if (avctx->request_channel_layout) {
+        av_channel_layout_uninit(&s->downmix_layout);
+        av_channel_layout_from_mask(&s->downmix_layout, avctx->request_channel_layout);
+    }
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
+    if (avctx->ch_layout.nb_channels > 1 &&
+        !av_channel_layout_compare(&s->downmix_layout, &mono)) {
+        av_channel_layout_uninit(&avctx->ch_layout);
+        avctx->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
+    } else if (avctx->ch_layout.nb_channels > 2 &&
+             !av_channel_layout_compare(&s->downmix_layout, &stereo)) {
+        av_channel_layout_uninit(&avctx->ch_layout);
+        avctx->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
+    }
+    s->downmixed = 1;
+}
+
 /**
  * AVCodec initialization
  */
@@ -190,8 +217,6 @@ static av_cold int ac3_decode_init(AVCodecContext *avctx)
 {
     static AVOnce init_static_once = AV_ONCE_INIT;
     AC3DecodeContext *s = avctx->priv_data;
-    const AVChannelLayout mono   = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
-    const AVChannelLayout stereo = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
     int i, ret;
 
     s->avctx = avctx;
@@ -219,25 +244,7 @@ static av_cold int ac3_decode_init(AVCodecContext *avctx)
     else
         avctx->sample_fmt = AV_SAMPLE_FMT_FLTP;
 
-    /* allow downmixing to stereo or mono */
-#if FF_API_OLD_CHANNEL_LAYOUT
-FF_DISABLE_DEPRECATION_WARNINGS
-    if (avctx->request_channel_layout) {
-        av_channel_layout_uninit(&s->downmix_layout);
-        av_channel_layout_from_mask(&s->downmix_layout, avctx->request_channel_layout);
-    }
-FF_ENABLE_DEPRECATION_WARNINGS
-#endif
-    if (avctx->ch_layout.nb_channels > 1 &&
-        !av_channel_layout_compare(&s->downmix_layout, &mono)) {
-        av_channel_layout_uninit(&avctx->ch_layout);
-        avctx->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
-    } else if (avctx->ch_layout.nb_channels > 2 &&
-             !av_channel_layout_compare(&s->downmix_layout, &stereo)) {
-        av_channel_layout_uninit(&avctx->ch_layout);
-        avctx->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO;
-    }
-    s->downmixed = 1;
+    ac3_downmix(avctx);
 
     for (i = 0; i < AC3_MAX_CHANNELS; i++) {
         s->xcfptr[i] = s->transform_coeffs[i];
@@ -1751,7 +1758,7 @@ skip:
                     if (index < 0)
                         return AVERROR_INVALIDDATA;
                     if (extend >= channel_map_size)
-                        return AVERROR_INVALIDDATA;
+                        break;
 
                     extended_channel_map[index] = offset + channel_map[extend++];
                 } else {
@@ -1763,7 +1770,7 @@ skip:
                             if (index < 0)
                                 return AVERROR_INVALIDDATA;
                             if (extend >= channel_map_size)
-                                return AVERROR_INVALIDDATA;
+                                break;
 
                             extended_channel_map[index] = offset + channel_map[extend++];
                         }
@@ -1771,6 +1778,8 @@ skip:
                 }
             }
         }
+
+        ac3_downmix(avctx);
     }
 
     /* get output buffer */