[FFmpeg-devel] [PATCH] AAC encoder: fix assertion error with prediction

Claudio Freire klaussfreire at gmail.com
Wed Jan 13 17:17:53 CET 2016

On Wed, Dec 30, 2015 at 10:44 PM, Claudio Freire <klaussfreire at gmail.com> wrote:
> On Tue, Dec 29, 2015 at 1:12 PM, Claudio Freire <klaussfreire at gmail.com> wrote:
>> On Tue, Dec 29, 2015 at 6:18 AM, Rostislav Pehlivanov
>> <atomnuker at gmail.com> wrote:
>>> Wouldn't it be simpler to just check if the maximum codebook was 0 after
>>> calculating cost1 and skipping the rest of the code in the loop?
>>> On 29 December 2015 at 08:23, Claudio Freire <klaussfreire at gmail.com> wrote:
>>>> Fixes an assertion error reported in #2686 that happens when
>>>> using prediction (either explicitly or implicitly by setting
>>>> the AAC main profile), since prediction code would allow
>>>> creating new zeroes or removing existing ones, without
>>>> properly checking for SF delta violations.
>>>> This patch forbids creating/removing zeroes, perhaps an
>>>> overly conservative approach, but a safe one. More permissive
>>>> and sophisticated approaches may be attempted in the future.
>> It is possible, and in fact does happen and it helps considerably to
>> hide some artifacts, to use prediction in zeroed bands.
>> It basically uses the predicted coefficient with no correction.
>> May well be better than using a zero.
> If there are no further objections I may push it soon.
> I've encoded and listened to lots of test samples without issue
> (though I'm testing other patches too).


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