From: Rodeo
Origin: https://github.com/HandBrake/HandBrake/blob/master/contrib/a52dec/A01-thread-safe.patch

diff -Naur a52dec.old/include/a52.h a52dec.new/include/a52.h
--- a52dec.old/include/a52.h	2012-07-16 14:24:14.000000000 +0200
+++ a52dec.new/include/a52.h	2012-07-16 14:31:37.000000000 +0200
@@ -42,6 +42,11 @@
 } expbap_t;
 
 typedef struct {
+    sample_t real;
+    sample_t imag;
+} complex_t;
+
+typedef struct {
     uint8_t fscod;            /* sample rate */
     uint8_t halfrate;         /* halfrate factor */
     uint8_t acmod;            /* coded channels */
@@ -94,6 +99,20 @@
 
     sample_t * samples;
     int downmixed;
+
+    /* Root values for IFFT */
+    sample_t * roots16;           // size 3
+    sample_t * roots32;           // size 7
+    sample_t * roots64;           // size 15
+    sample_t * roots128;          // size 31
+
+    /* Twiddle factors for IMDCT */
+    complex_t * pre1;             // size 128
+    complex_t * post1;            // size 64
+    complex_t * pre2;             // size 64
+    complex_t * post2;            // size 32
+
+    sample_t * a52_imdct_window;  // size 256
 } a52_state_t;
 
 #define A52_CHANNEL 0
diff -Naur a52dec.old/liba52/a52_internal.h a52dec.new/liba52/a52_internal.h
--- a52dec.old/liba52/a52_internal.h	2012-07-16 14:24:14.000000000 +0200
+++ a52dec.new/liba52/a52_internal.h	2012-07-16 14:28:33.000000000 +0200
@@ -49,6 +49,6 @@
 		  sample_t clev, sample_t slev);
 void a52_upmix (sample_t * samples, int acmod, int output);
 
-void a52_imdct_init (uint32_t mm_accel);
-void a52_imdct_256 (sample_t * data, sample_t * delay, sample_t bias);
-void a52_imdct_512 (sample_t * data, sample_t * delay, sample_t bias);
+void a52_imdct_init (a52_state_t * state, uint32_t mm_accel);
+void a52_imdct_256 (a52_state_t * state, sample_t * data, sample_t * delay, sample_t bias);
+void a52_imdct_512 (a52_state_t * state, sample_t * data, sample_t * delay, sample_t bias);
diff -Naur a52dec.old/liba52/imdct.c a52dec.new/liba52/imdct.c
--- a52dec.old/liba52/imdct.c	2012-07-16 14:24:14.000000000 +0200
+++ a52dec.new/liba52/imdct.c	2012-07-16 14:33:00.000000000 +0200
@@ -40,11 +40,6 @@
 #include "a52_internal.h"
 #include "mm_accel.h"
 
-typedef struct complex_s {
-    sample_t real;
-    sample_t imag;
-} complex_t;
-
 static uint8_t fftorder[] = {
       0,128, 64,192, 32,160,224, 96, 16,144, 80,208,240,112, 48,176,
       8,136, 72,200, 40,168,232,104,248,120, 56,184, 24,152,216, 88,
@@ -56,22 +51,8 @@
       6,134, 70,198, 38,166,230,102,246,118, 54,182, 22,150,214, 86
 };
 
-/* Root values for IFFT */
-static sample_t roots16[3];
-static sample_t roots32[7];
-static sample_t roots64[15];
-static sample_t roots128[31];
-
-/* Twiddle factors for IMDCT */
-static complex_t pre1[128];
-static complex_t post1[64];
-static complex_t pre2[64];
-static complex_t post2[32];
-
-static sample_t a52_imdct_window[256];
-
-static void (* ifft128) (complex_t * buf);
-static void (* ifft64) (complex_t * buf);
+static void (* ifft128) (a52_state_t * state, complex_t * buf);
+static void (* ifft64) (a52_state_t * state, complex_t * buf);
 
 static inline void ifft2 (complex_t * buf)
 {
@@ -167,7 +148,7 @@
     a1.imag += tmp4;				\
 } while (0)
 
-static inline void ifft8 (complex_t * buf)
+static inline void ifft8 (a52_state_t * state, complex_t * buf)
 {
     double tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7, tmp8;
 
@@ -175,7 +156,7 @@
     ifft2 (buf + 4);
     ifft2 (buf + 6);
     BUTTERFLY_ZERO (buf[0], buf[2], buf[4], buf[6]);
-    BUTTERFLY_HALF (buf[1], buf[3], buf[5], buf[7], roots16[1]);
+    BUTTERFLY_HALF (buf[1], buf[3], buf[5], buf[7], state->roots16[1]);
 }
 
 static void ifft_pass (complex_t * buf, sample_t * weight, int n)
@@ -205,66 +186,66 @@
     } while (--i);
 }
 
-static void ifft16 (complex_t * buf)
+static void ifft16 (a52_state_t * state, complex_t * buf)
 {
-    ifft8 (buf);
+    ifft8 (state, buf);
     ifft4 (buf + 8);
     ifft4 (buf + 12);
-    ifft_pass (buf, roots16 - 4, 4);
+    ifft_pass (buf, state->roots16 - 4, 4);
 }
 
-static void ifft32 (complex_t * buf)
+static void ifft32 (a52_state_t * state, complex_t * buf)
 {
-    ifft16 (buf);
-    ifft8 (buf + 16);
-    ifft8 (buf + 24);
-    ifft_pass (buf, roots32 - 8, 8);
+    ifft16 (state, buf);
+    ifft8 (state, buf + 16);
+    ifft8 (state, buf + 24);
+    ifft_pass (buf, state->roots32 - 8, 8);
 }
 
-static void ifft64_c (complex_t * buf)
+static void ifft64_c (a52_state_t * state, complex_t * buf)
 {
-    ifft32 (buf);
-    ifft16 (buf + 32);
-    ifft16 (buf + 48);
-    ifft_pass (buf, roots64 - 16, 16);
+    ifft32 (state, buf);
+    ifft16 (state, buf + 32);
+    ifft16 (state, buf + 48);
+    ifft_pass (buf, state->roots64 - 16, 16);
 }
 
-static void ifft128_c (complex_t * buf)
+static void ifft128_c (a52_state_t * state, complex_t * buf)
 {
-    ifft32 (buf);
-    ifft16 (buf + 32);
-    ifft16 (buf + 48);
-    ifft_pass (buf, roots64 - 16, 16);
+    ifft32 (state, buf);
+    ifft16 (state, buf + 32);
+    ifft16 (state, buf + 48);
+    ifft_pass (buf, state->roots64 - 16, 16);
 
-    ifft32 (buf + 64);
-    ifft32 (buf + 96);
-    ifft_pass (buf, roots128 - 32, 32);
+    ifft32 (state, buf + 64);
+    ifft32 (state, buf + 96);
+    ifft_pass (buf, state->roots128 - 32, 32);
 }
 
-void a52_imdct_512 (sample_t * data, sample_t * delay, sample_t bias)
+void a52_imdct_512 (a52_state_t * state, sample_t * data, sample_t * delay, sample_t bias)
 {
     int i, k;
     sample_t t_r, t_i, a_r, a_i, b_r, b_i, w_1, w_2;
-    const sample_t * window = a52_imdct_window;
+    const sample_t * window = state->a52_imdct_window;
     complex_t buf[128];
 	
     for (i = 0; i < 128; i++) {
 	k = fftorder[i];
-	t_r = pre1[i].real;
-	t_i = pre1[i].imag;
+	t_r = state->pre1[i].real;
+	t_i = state->pre1[i].imag;
 
 	buf[i].real = t_i * data[255-k] + t_r * data[k];
 	buf[i].imag = t_r * data[255-k] - t_i * data[k];
     }
 
-    ifft128 (buf);
+    ifft128 (state, buf);
 
     /* Post IFFT complex multiply plus IFFT complex conjugate*/
     /* Window and convert to real valued signal */
     for (i = 0; i < 64; i++) {
 	/* y[n] = z[n] * (xcos1[n] + j * xsin1[n]) ; */
-	t_r = post1[i].real;
-	t_i = post1[i].imag;
+	t_r = state->post1[i].real;
+	t_i = state->post1[i].imag;
 
 	a_r = t_r * buf[i].real     + t_i * buf[i].imag;
 	a_i = t_i * buf[i].real     - t_r * buf[i].imag;
@@ -285,18 +266,18 @@
     }
 }
 
-void a52_imdct_256(sample_t * data, sample_t * delay, sample_t bias)
+void a52_imdct_256(a52_state_t * state, sample_t * data, sample_t * delay, sample_t bias)
 {
     int i, k;
     sample_t t_r, t_i, a_r, a_i, b_r, b_i, c_r, c_i, d_r, d_i, w_1, w_2;
-    const sample_t * window = a52_imdct_window;
+    const sample_t * window = state->a52_imdct_window;
     complex_t buf1[64], buf2[64];
 
     /* Pre IFFT complex multiply plus IFFT cmplx conjugate */
     for (i = 0; i < 64; i++) {
 	k = fftorder[i];
-	t_r = pre2[i].real;
-	t_i = pre2[i].imag;
+	t_r = state->pre2[i].real;
+	t_i = state->pre2[i].imag;
 
 	buf1[i].real = t_i * data[254-k] + t_r * data[k];
 	buf1[i].imag = t_r * data[254-k] - t_i * data[k];
@@ -305,15 +286,15 @@
 	buf2[i].imag = t_r * data[255-k] - t_i * data[k+1];
     }
 
-    ifft64 (buf1);
-    ifft64 (buf2);
+    ifft64 (state, buf1);
+    ifft64 (state, buf2);
 
     /* Post IFFT complex multiply */
     /* Window and convert to real valued signal */
     for (i = 0; i < 32; i++) {
 	/* y1[n] = z1[n] * (xcos2[n] + j * xs in2[n]) ; */ 
-	t_r = post2[i].real;
-	t_i = post2[i].imag;
+	t_r = state->post2[i].real;
+	t_i = state->post2[i].imag;
 
 	a_r = t_r * buf1[i].real    + t_i * buf1[i].imag;
 	a_i = t_i * buf1[i].real    - t_r * buf1[i].imag;
@@ -362,7 +343,7 @@
     return bessel;
 }
 
-void a52_imdct_init (uint32_t mm_accel)
+void a52_imdct_init (a52_state_t * state, uint32_t mm_accel)
 {
     int i, k;
     double sum;
@@ -371,50 +352,50 @@
     sum = 0;
     for (i = 0; i < 256; i++) {
 	sum += besselI0 (i * (256 - i) * (5 * M_PI / 256) * (5 * M_PI / 256));
-	a52_imdct_window[i] = sum;
+	state->a52_imdct_window[i] = sum;
     }
     sum++;
     for (i = 0; i < 256; i++)
-	a52_imdct_window[i] = sqrt (a52_imdct_window[i] / sum);
+	state->a52_imdct_window[i] = sqrt (state->a52_imdct_window[i] / sum);
 
     for (i = 0; i < 3; i++)
-	roots16[i] = cos ((M_PI / 8) * (i + 1));
+	state->roots16[i] = cos ((M_PI / 8) * (i + 1));
 
     for (i = 0; i < 7; i++)
-	roots32[i] = cos ((M_PI / 16) * (i + 1));
+	state->roots32[i] = cos ((M_PI / 16) * (i + 1));
 
     for (i = 0; i < 15; i++)
-	roots64[i] = cos ((M_PI / 32) * (i + 1));
+	state->roots64[i] = cos ((M_PI / 32) * (i + 1));
 
     for (i = 0; i < 31; i++)
-	roots128[i] = cos ((M_PI / 64) * (i + 1));
+	state->roots128[i] = cos ((M_PI / 64) * (i + 1));
 
     for (i = 0; i < 64; i++) {
 	k = fftorder[i] / 2 + 64;
-	pre1[i].real = cos ((M_PI / 256) * (k - 0.25));
-	pre1[i].imag = sin ((M_PI / 256) * (k - 0.25));
+	state->pre1[i].real = cos ((M_PI / 256) * (k - 0.25));
+	state->pre1[i].imag = sin ((M_PI / 256) * (k - 0.25));
     }
 
     for (i = 64; i < 128; i++) {
 	k = fftorder[i] / 2 + 64;
-	pre1[i].real = -cos ((M_PI / 256) * (k - 0.25));
-	pre1[i].imag = -sin ((M_PI / 256) * (k - 0.25));
+	state->pre1[i].real = -cos ((M_PI / 256) * (k - 0.25));
+	state->pre1[i].imag = -sin ((M_PI / 256) * (k - 0.25));
     }
 
     for (i = 0; i < 64; i++) {
-	post1[i].real = cos ((M_PI / 256) * (i + 0.5));
-	post1[i].imag = sin ((M_PI / 256) * (i + 0.5));
+	state->post1[i].real = cos ((M_PI / 256) * (i + 0.5));
+	state->post1[i].imag = sin ((M_PI / 256) * (i + 0.5));
     }
 
     for (i = 0; i < 64; i++) {
 	k = fftorder[i] / 4;
-	pre2[i].real = cos ((M_PI / 128) * (k - 0.25));
-	pre2[i].imag = sin ((M_PI / 128) * (k - 0.25));
+	state->pre2[i].real = cos ((M_PI / 128) * (k - 0.25));
+	state->pre2[i].imag = sin ((M_PI / 128) * (k - 0.25));
     }
 
     for (i = 0; i < 32; i++) {
-	post2[i].real = cos ((M_PI / 128) * (i + 0.5));
-	post2[i].imag = sin ((M_PI / 128) * (i + 0.5));
+	state->post2[i].real = cos ((M_PI / 128) * (i + 0.5));
+	state->post2[i].imag = sin ((M_PI / 128) * (i + 0.5));
     }
 
 #ifdef LIBA52_DJBFFT
diff -Naur a52dec.old/liba52/parse.c a52dec.new/liba52/parse.c
--- a52dec.old/liba52/parse.c	2012-07-16 14:24:14.000000000 +0200
+++ a52dec.new/liba52/parse.c	2012-07-16 14:33:00.000000000 +0200
@@ -56,16 +56,53 @@
     a52_state_t * state;
     int i;
 
-    state = malloc (sizeof (a52_state_t));
+    state = calloc (1, sizeof (a52_state_t));
     if (state == NULL)
 	return NULL;
 
     state->samples = memalign (16, 256 * 12 * sizeof (sample_t));
     if (state->samples == NULL) {
-	free (state);
-	return NULL;
+        goto fail;
     }
 
+    /* Root values for IFFT */
+    state->roots16 = memalign (16, 3 * sizeof (sample_t));
+    if (state->roots16 == NULL)
+        goto fail;
+
+    state->roots32 = memalign (16, 7 * sizeof (sample_t));
+    if (state->roots32 == NULL)
+        goto fail;
+
+    state->roots64 = memalign (16, 15 * sizeof (sample_t));
+    if (state->roots64 == NULL)
+        goto fail;
+
+    state->roots128 = memalign (16, 31 * sizeof (sample_t));
+    if (state->roots128 == NULL)
+        goto fail;
+
+    /* Twiddle factors for IMDCT */
+    state->pre1 = memalign (16, 128 * sizeof (complex_t));
+    if (state->pre1 == NULL)
+        goto fail;
+
+    state->post1 = memalign (16, 64 * sizeof (complex_t));
+    if (state->post1 == NULL)
+        goto fail;
+
+    state->pre2 = memalign (16, 64 * sizeof (complex_t));
+    if (state->pre2 == NULL)
+        goto fail;
+
+    state->post2 = memalign (16, 32 * sizeof (complex_t));
+    if (state->post2 == NULL)
+        goto fail;
+
+    state->a52_imdct_window = memalign (16, 256 * sizeof (sample_t));
+    if (state->a52_imdct_window == NULL)
+        goto fail;
+
     for (i = 0; i < 256 * 12; i++)
 	state->samples[i] = 0;
 
@@ -73,9 +110,27 @@
 
     state->lfsr_state = 1;
 
-    a52_imdct_init (mm_accel);
+    a52_imdct_init (state, mm_accel);
 
     return state;
+
+fail:
+    if ( state )
+    {
+        free (state->a52_imdct_window);
+        free (state->post2);
+        free (state->pre2);
+        free (state->post1);
+        free (state->pre1);
+        free (state->roots128);
+        free (state->roots64);
+        free (state->roots32);
+        free (state->roots16);
+        free (state->samples);
+        free (state);
+    }
+    return NULL;
+
 }
 
 sample_t * a52_samples (a52_state_t * state)
@@ -825,7 +880,7 @@
 		       state->dynrng, 0, 7);
 	    for (i = 7; i < 256; i++)
 		(samples-256)[i] = 0;
-	    a52_imdct_512 (samples - 256, samples + 1536 - 256, state->bias);
+	    a52_imdct_512 (state, samples - 256, samples + 1536 - 256, state->bias);
 	} else {
 	    /* just skip the LFE coefficients */
 	    coeff_get (state, samples + 1280, &state->lfe_expbap, &quantizer,
@@ -854,10 +909,10 @@
 
 	    if (coeff[i]) {
 		if (blksw[i])
-		    a52_imdct_256 (samples + 256 * i, samples + 1536 + 256 * i,
+		    a52_imdct_256 (state, samples + 256 * i, samples + 1536 + 256 * i,
 				   bias);
 		else 
-		    a52_imdct_512 (samples + 256 * i, samples + 1536 + 256 * i,
+		    a52_imdct_512 (state, samples + 256 * i, samples + 1536 + 256 * i,
 				   bias);
 	    } else {
 		int j;
@@ -883,11 +938,11 @@
 
 	if (blksw[0])
 	    for (i = 0; i < nfchans; i++)
-		a52_imdct_256 (samples + 256 * i, samples + 1536 + 256 * i,
+		a52_imdct_256 (state, samples + 256 * i, samples + 1536 + 256 * i,
 			       state->bias);
 	else 
 	    for (i = 0; i < nfchans; i++)
-		a52_imdct_512 (samples + 256 * i, samples + 1536 + 256 * i,
+		a52_imdct_512 (state, samples + 256 * i, samples + 1536 + 256 * i,
 			       state->bias);
     }
 
@@ -896,6 +951,15 @@
 
 void a52_free (a52_state_t * state)
 {
+    free (state->a52_imdct_window);
+    free (state->post2);
+    free (state->pre2);
+    free (state->post1);
+    free (state->pre1);
+    free (state->roots128);
+    free (state->roots64);
+    free (state->roots32);
+    free (state->roots16);
     free (state->samples);
     free (state);
 }