diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 663acc0ac9..9c0ed7dccb 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -38,9 +38,6 @@
 #include "ac3dec_data.h"
 #include "kbdwin.h"
 
-/** Large enough for maximum possible frame size when the specification limit is ignored */
-#define AC3_FRAME_BUFFER_SIZE 32768
-
 /**
  * table for ungrouping 3 values in 7 bits.
  * used for exponents and bap=2 mantissas
@@ -206,11 +203,6 @@ static av_cold int ac3_decode_init(AVCodecContext *avctx)
     }
     s->downmixed = 1;
 
-    /* allocate context input buffer */
-        s->input_buffer = av_mallocz(AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
-        if (!s->input_buffer)
-            return AVERROR(ENOMEM);
-
     return 0;
 }
 
@@ -1436,8 +1428,6 @@ static av_cold int ac3_decode_end(AVCodecContext *avctx)
     ff_mdct_end(&s->imdct_512);
     ff_mdct_end(&s->imdct_256);
 
-    av_freep(&s->input_buffer);
-
     return 0;
 }
 
diff --git a/libavcodec/ac3dec.h b/libavcodec/ac3dec.h
index a7cebafbe9..38262514b6 100644
--- a/libavcodec/ac3dec.h
+++ b/libavcodec/ac3dec.h
@@ -62,11 +62,13 @@
 
 #define SPX_MAX_BANDS    17
 
+/** Large enough for maximum possible frame size when the specification limit is ignored */
+#define AC3_FRAME_BUFFER_SIZE 32768
+
 typedef struct {
     AVClass        *class;                  ///< class for AVOptions
     AVCodecContext *avctx;                  ///< parent context
     GetBitContext gbc;                      ///< bitstream reader
-    uint8_t *input_buffer;                  ///< temp buffer to prevent overread
 
 ///@name Bit stream information
 ///@{
@@ -202,6 +204,7 @@ typedef struct {
     DECLARE_ALIGNED(32, float, window)[AC3_BLOCK_SIZE];                              ///< window coefficients
     DECLARE_ALIGNED(32, float, tmp_output)[AC3_BLOCK_SIZE];                          ///< temporary storage for output before windowing
     DECLARE_ALIGNED(32, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE];            ///< output after imdct transform and windowing
+    DECLARE_ALIGNED(32, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
 ///@}
 } AC3DecodeContext;