On Thu, Apr 28, 2011 at 5:04 AM, Måns Rullgård <m...@mansr.com> wrote:
> Aℓex Converse <aconve...@google.com> writes:
>
>> There is most likely a performance hit here but the current code is
>> *undefined.*
>>
>> Haters are welcome to send suggestions on how to do this without an if.
>>
>> From 554be95192ad9803f51f00fec18bf6db9a562779 Mon Sep 17 00:00:00 2001
>> From: Alex Converse <aconve...@google.com>
>> Date: Tue, 26 Apr 2011 09:07:43 -0700
>> Subject: [PATCH 2/4] aacdec: Guard undefined shifts with an if.
>> MIME-Version: 1.0
>> Content-Type: multipart/mixed; boundary="------------1"
>>
>> This is a multi-part message in MIME format.
>> --------------1
>> Content-Type: text/plain; charset=UTF-8; format=fixed
>> Content-Transfer-Encoding: 8bit
>>
>> ---
>> libavcodec/aacdec.c | 7 +++++--
>> 1 files changed, 5 insertions(+), 2 deletions(-)
>>
>> --------------1
>> Content-Type: text/x-patch;
>> name="0002-aacdec-Guard-undefined-shifts-with-an-if.patch"
>> Content-Transfer-Encoding: 8bit
>> Content-Disposition: attachment;
>> filename="0002-aacdec-Guard-undefined-shifts-with-an-if.patch"
>
> Please configure your git to not do that.
It's not git. It's the mailer.
>
>> diff --git a/libavcodec/aacdec.c b/libavcodec/aacdec.c
>> index 0c6312f..c9f2afd 100644
>> --- a/libavcodec/aacdec.c
>> +++ b/libavcodec/aacdec.c
>> @@ -1083,8 +1083,11 @@ static int decode_spectrum_and_dequant(AACContext
>> *ac, float coef[1024],
>> GET_VLC(code, re, gb, vlc_tab, 8, 2);
>> cb_idx = cb_vector_idx[code];
>> nnz = cb_idx >> 8 & 15;
>> - bits = SHOW_UBITS(re, gb, nnz) << (32-nnz);
>> - LAST_SKIP_BITS(re, gb, nnz);
>> + if (nnz) {
>> + bits = SHOW_UBITS(re, gb, nnz) << (32-nnz);
>> + LAST_SKIP_BITS(re, gb, nnz);
>> + } else
>> + bits = 0;
>
> Does this ever happen?
>
yes
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