On 09.11.2016 02:27, Michael Niedermayer wrote:
> On Tue, Nov 08, 2016 at 10:36:01PM +0100, Andreas Cadhalpun wrote:
>> Since the loop goes down to i = 0 the number of iterations (variable
>> count) is the original i, not i - 1.
>> In the case of i originally being 1, this miscalculation resulted in
>> a division by zero.
>>
>> This problem was introduced in commit
>> 4b90dcb8493552c17a811c8b1e6538dae4061f9d.
>>
>> Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
>> ---
>> libavcodec/dvbsubdec.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavcodec/dvbsubdec.c b/libavcodec/dvbsubdec.c
>> index e9f4765..31898ea 100644
>> --- a/libavcodec/dvbsubdec.c
>> +++ b/libavcodec/dvbsubdec.c
>> @@ -810,7 +810,7 @@ static void compute_default_clut(AVSubtitleRect *rect,
>> int w, int h)
>> list_inv[ i ] = bestv;
>> }
>>
>> - count = i - 1;
>> + count = i;
>> for (i--; i>=0; i--) {
>> int v = i*255/count;
>> AV_WN32(rect->data[1] + 4*list_inv[i], RGBA(v/2,v,v/2,v));
>
> with this a 2 color text would be 50% and 100% transparent
> it should be transparent background and opaque text,
> count = FFMAX(i - 1, 1);
> seems better to me
OK, patch doing that is attached.
Best regards,
Andreas
>From 436318575abf482e1ea144f651c47bc2730e41a2 Mon Sep 17 00:00:00 2001
From: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
Date: Tue, 8 Nov 2016 22:32:42 +0100
Subject: [PATCH] dvbsubdec: fix division by zero in compute_default_clut
This problem was introduced in commit
4b90dcb8493552c17a811c8b1e6538dae4061f9d.
Signed-off-by: Andreas Cadhalpun <andreas.cadhal...@googlemail.com>
---
libavcodec/dvbsubdec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavcodec/dvbsubdec.c b/libavcodec/dvbsubdec.c
index e9f4765..bf3b1a1 100644
--- a/libavcodec/dvbsubdec.c
+++ b/libavcodec/dvbsubdec.c
@@ -810,7 +810,7 @@ static void compute_default_clut(AVSubtitleRect *rect, int w, int h)
list_inv[ i ] = bestv;
}
- count = i - 1;
+ count = FFMAX(i - 1, 1);
for (i--; i>=0; i--) {
int v = i*255/count;
AV_WN32(rect->data[1] + 4*list_inv[i], RGBA(v/2,v,v/2,v));
--
2.10.2
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