[FFmpeg-devel] [PATCH] ac3dec: avoid pointless alloc and indirection for input_buffer

[Reimar Döffinger]

Since we now always allocate it, it can simply be made part of the context
instead.
---
 libavcodec/ac3dec.c |   10 ----------
 libavcodec/ac3dec.h |    6 +++++-
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/libavcodec/ac3dec.c b/libavcodec/ac3dec.c
index 7f12d9c..d4e36c1 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
@@ -208,11 +205,6 @@ 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);
-
     avctx->sample_fmt = AV_SAMPLE_FMT_S16;
     return 0;
 }
@@ -1425,8 +1417,6 @@ 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 a5b1111..ac259ee 100644
--- a/libavcodec/ac3dec.h
+++ b/libavcodec/ac3dec.h
@@ -66,10 +66,14 @@
 
 #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 {
+    /** temp buffer to prevent overread, must be first to ensure alignment */
+    uint8_t input_buffer[AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE];
     AVCodecContext *avctx;                  ///< parent context
     GetBitContext gbc;                      ///< bitstream reader
-    uint8_t *input_buffer;                  ///< temp buffer to prevent overread
 
 ///@defgroup bsi bit stream information
 ///@{
-- 
1.7.4.1