diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index b0e7647877..5ef576ae0d 100644
--- a/libavcodec/ac3dec.c
+++ b/libavcodec/ac3dec.c
@@ -37,9 +37,6 @@
 #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
@@ -204,11 +201,6 @@ 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);
-
     /* ffdshow custom code */
 #if CONFIG_AUDIO_FLOAT
     avctx->sample_fmt = AV_SAMPLE_FMT_FLT;
@@ -1441,8 +1433,6 @@ 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 3e0afcded0..91008e5c8f 100644
--- a/libavcodec/ac3dec.h
+++ b/libavcodec/ac3dec.h
@@ -67,10 +67,12 @@
 
 #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 {
     AVCodecContext *avctx;                  ///< parent context
     GetBitContext gbc;                      ///< bitstream reader
-    uint8_t *input_buffer;                  ///< temp buffer to prevent overread
 
 ///@defgroup bsi bit stream information
 ///@{
@@ -205,6 +207,7 @@ typedef struct {
     DECLARE_ALIGNED(16, float, window)[AC3_BLOCK_SIZE];                              ///< window coefficients
     DECLARE_ALIGNED(16, float, tmp_output)[AC3_BLOCK_SIZE];                          ///< temporary storage for output before windowing
     DECLARE_ALIGNED(16, float, output)[AC3_MAX_CHANNELS][AC3_BLOCK_SIZE];            ///< output after imdct transform and windowing
+    DECLARE_ALIGNED(16, uint8_t, input_buffer)[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE]; ///< temp buffer to prevent overread
 ///@}
 } AC3DecodeContext;