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[ffmpeg/armv6] fixed #13414 broken ac3 on armv6

backported ffmpeg commit cd2f98f365dfd83f0debac030413e57a73c7ecd5 which fixes ac3 on armv6

20:21:47 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] exponent out-of-range
20:21:47 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] error decoding the audio block
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] exponent out-of-range
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] error decoding the audio block
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] exponent out-of-range
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] error decoding the audio block
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] exponent out-of-range
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] error decoding the audio block
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] exponent out-of-range
20:21:48 T:1403229280   ERROR: ffmpeg[53A39460]: [ac3] error decoding the audio block

This log was observed on a RaspberryPI which is armv6.
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1 parent c4ed280 commit 42a68dd5eb5637adee3ec159f284d84780b1da26 @huceke committed Oct 15, 2012
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15 lib/ffmpeg/libavcodec/arm/ac3dsp_armv6.S
@@ -34,24 +34,23 @@ function ff_ac3_bit_alloc_calc_bap_armv6, export=1
add r0, r0, r4, lsl #1 @ mask + band
add r4, lr, r4
add r7, r7, r2 @ bap + start
- ldrb r10, [r4], #1
1:
ldrsh r9, [r0], #2 @ mask[band]
mov r8, #0xff0
sub r9, r9, r12 @ - snr_offset
- mov r11, r10
- ldrb r10, [r4], #1 @ band_start_tab[band++]
+ ldrb r10, [r4, #1]! @ band_start_tab[++band]
subs r9, r9, r5 @ - floor
it lt
movlt r9, #0
cmp r10, r3 @ - end
and r9, r9, r8, lsl #1 @ & 0x1fe0
ite gt
- subgt r8, r3, r11
- suble r8, r10, r11
+ subgt r8, r3, r2
+ suble r8, r10, r2
+ mov r2, r10
add r9, r9, r5 @ + floor => m
tst r8, #1
- add r2, r7, r8
+ add r11, r7, r8
bne 3f
b 5f
2:
@@ -65,9 +64,9 @@ function ff_ac3_bit_alloc_calc_bap_armv6, export=1
ldrb lr, [r6, lr]
strb r8, [r7], #1 @ bap[bin]
strb lr, [r7], #1
-5: cmp r7, r2
+5: cmp r7, r11
blo 2b
- cmp r3, r11
+ cmp r3, r10
bgt 1b
pop {r4-r11,pc}
3:
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62 lib/ffmpeg/patches/0033-ARM-ac3-fix-ac3_bit_alloc_calc_bap_armv6.patch
@@ -0,0 +1,62 @@
+From cd2f98f365dfd83f0debac030413e57a73c7ecd5 Mon Sep 17 00:00:00 2001
+From: Mans Rullgard <mans@mansr.com>
+Date: Wed, 1 Feb 2012 22:25:10 +0000
+Subject: [PATCH] ARM: ac3: fix ac3_bit_alloc_calc_bap_armv6
+
+This function was broken when the start bin was not at the start
+of a band.
+
+Signed-off-by: Mans Rullgard <mans@mansr.com>
+---
+ libavcodec/arm/ac3dsp_armv6.S | 15 +++++++--------
+ 1 file changed, 7 insertions(+), 8 deletions(-)
+
+diff --git a/libavcodec/arm/ac3dsp_armv6.S b/libavcodec/arm/ac3dsp_armv6.S
+index b6aee86..df8bfba 100644
+--- a/libavcodec/arm/ac3dsp_armv6.S
++++ b/libavcodec/arm/ac3dsp_armv6.S
+@@ -34,24 +34,23 @@ function ff_ac3_bit_alloc_calc_bap_armv6, export=1
+ add r0, r0, r4, lsl #1 @ mask + band
+ add r4, lr, r4
+ add r7, r7, r2 @ bap + start
+- ldrb r10, [r4], #1
+ 1:
+ ldrsh r9, [r0], #2 @ mask[band]
+ mov r8, #0xff0
+ sub r9, r9, r12 @ - snr_offset
+- mov r11, r10
+- ldrb r10, [r4], #1 @ band_start_tab[band++]
++ ldrb r10, [r4, #1]! @ band_start_tab[++band]
+ subs r9, r9, r5 @ - floor
+ it lt
+ movlt r9, #0
+ cmp r10, r3 @ - end
+ and r9, r9, r8, lsl #1 @ & 0x1fe0
+ ite gt
+- subgt r8, r3, r11
+- suble r8, r10, r11
++ subgt r8, r3, r2
++ suble r8, r10, r2
++ mov r2, r10
+ add r9, r9, r5 @ + floor => m
+ tst r8, #1
+- add r2, r7, r8
++ add r11, r7, r8
+ bne 3f
+ b 5f
+ 2:
+@@ -65,9 +64,9 @@ function ff_ac3_bit_alloc_calc_bap_armv6, export=1
+ ldrb lr, [r6, lr]
+ strb r8, [r7], #1 @ bap[bin]
+ strb lr, [r7], #1
+-5: cmp r7, r2
++5: cmp r7, r11
+ blo 2b
+- cmp r3, r11
++ cmp r3, r10
+ bgt 1b
+ pop {r4-r11,pc}
+ 3:
+--
+1.7.10.4
+

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