diff --git a/ext/at3_standalone/atrac3plus.cpp b/ext/at3_standalone/atrac3plus.cpp
index 01a5fbe801..0844deed59 100644
--- a/ext/at3_standalone/atrac3plus.cpp
+++ b/ext/at3_standalone/atrac3plus.cpp
@@ -815,16 +815,6 @@ static int decode_code_table_indexes(GetBitContext *gb, Atrac3pChanUnitCtx *ctx,
     return 0;
 }
 
-/**
- * Clear high bits from an unsigned integer starting with specific bit position
- * @param  a value to clip
- * @param  p bit position to clip at
- * @return clipped value
- */
-inline unsigned av_mod_uintp2(unsigned a, unsigned p) {
-    return a & ((1 << p) - 1);
-}
-
 /**
  * Decode huffman-coded spectral lines for a given quant unit.
  *
@@ -846,21 +836,21 @@ static void decode_qu_spectra(GetBitContext *gb, const Atrac3pSpecCodeTab *tab,
     int bits       = tab->bits;
     int is_signed  = tab->is_signed;
     unsigned val;
+    const unsigned bitmask = ((1 << bits) - 1);  // mask to clear higher bits.
 
     for (pos = 0; pos < num_specs;) {
         if (group_size == 1 || get_bits1(gb)) {
             for (j = 0; j < group_size; j++) {
                 val = get_vlc2(gb, vlc_tab->table, vlc_tab->bits, 1);
-
                 for (i = 0; i < num_coeffs; i++) {
-                    cf = av_mod_uintp2(val, bits);
+                    cf = val & bitmask;
                     if (is_signed)
                         cf = sign_extend(cf, bits);
                     else if (cf && get_bits1(gb))
                         cf = -cf;
 
                     out[pos++] = cf;
-                    val      >>= bits;
+                    val >>= bits;
                 }
             }
         } else /* group skipped */
diff --git a/ext/at3_standalone/compat.h b/ext/at3_standalone/compat.h
index 57b0244de4..f282f0c9c5 100644
--- a/ext/at3_standalone/compat.h
+++ b/ext/at3_standalone/compat.h
@@ -37,10 +37,6 @@
 #define av_printf_format(a,b)
 #define avpriv_report_missing_feature(...)
 
-#define AV_NOPTS_VALUE          ((int64_t)UINT64_C(0x8000000000000000))
-#define AV_TIME_BASE            1000000
-#define AV_TIME_BASE_Q          (AVRational){1, AV_TIME_BASE}
-
 #define AVERROR(e) (-(e))   ///< Returns a negative error code from a POSIX error code, to return from library functions.
 #define AVUNERROR(e) (-(e)) ///< Returns a POSIX error code from a library function error return value.
 
@@ -49,8 +45,6 @@
 #define AVERROR_INVALIDDATA        FFERRTAG( 'I','N','D','A') ///< Invalid data found when processing input
 #define AVERROR_PATCHWELCOME       FFERRTAG( 'P','A','W','E') ///< Not yet implemented in FFmpeg, patches welcome
 
-#define FF_SANE_NB_CHANNELS 64U
-
 #define AV_LOG_ERROR    16
 #define AV_LOG_WARNING  24
 #define AV_LOG_INFO     32
@@ -60,13 +54,6 @@
 
 void av_log(int level, const char *fmt, ...) av_printf_format(3, 4);
 
-/**
- * Maximum size in bytes of extradata.
- * This value was chosen such that every bit of the buffer is
- * addressable by a 32-bit signed integer as used by get_bits.
- */
-#define FF_MAX_EXTRADATA_SIZE ((1 << 28) - AV_INPUT_BUFFER_PADDING_SIZE)
-
  /**
   * Absolute value, Note, INT_MIN / INT64_MIN result in undefined behavior as they
   * are not representable as absolute values of their type. This is the same
diff --git a/ext/at3_standalone/get_bits.cpp b/ext/at3_standalone/get_bits.cpp
index 4c7725f89b..50d3969219 100644
--- a/ext/at3_standalone/get_bits.cpp
+++ b/ext/at3_standalone/get_bits.cpp
@@ -87,7 +87,7 @@ static int alloc_table(VLC *vlc, int size, int use_static)
             vlc->table_size = 0;
             return AVERROR(ENOMEM);
         }
-        memset(vlc->table + vlc->table_allocated - (1 << vlc->bits), 0, sizeof(VLC_TYPE) * 2 << vlc->bits);
+        memset(vlc->table + vlc->table_allocated - (unsigned int)(1UL << vlc->bits), 0, sizeof(VLC_TYPE) * 2 << vlc->bits);
     }
     return index;
 }