[FFmpeg-devel] [PATCH][RFC] avcodec: disallow hwaccel with frame threads

[Hendrik Leppkes]

On Tue, Jan 19, 2016 at 9:27 PM, Andreas Cadhalpun
<andreas.cadhalpun at googlemail.com> wrote:
> On 19.01.2016 21:22, Hendrik Leppkes wrote:
>> On Tue, Jan 19, 2016 at 9:13 PM, Andreas Cadhalpun
>> <andreas.cadhalpun at googlemail.com> wrote:
>>> On 22.10.2015 11:44, Hendrik Leppkes wrote:
>>>> On Thu, Oct 22, 2015 at 11:27 AM, Wang Bin <wbsecg1 at gmail.com> wrote:
>>>>> VLC is using frame threading with hwaccel
>>>>
>>>> Then they should fix their usage, its broken by design, as explained
>>>> in detail my post earlier in this thread.
>>>
>>> Care to provide a patch for them?
>>
>>
>> This requires deep understanding of the code in question, so nothing
>> anyone not familiar with the code can easily fix, so no patches for
>> downstreams will be provided.
>
> That suggests that fixing it properly requires a lot of time.
>
>>> They now made VLC's configure error out when compiling with FFmpeg [1],
>>> because they currently lack time [2] to fix this the way you suggest
>>> and Libav doesn't return this error.
>>>
>>
>> They don't lack time, they lack understanding of the flaws in the system.
>
> How can you know that?

Because I read the ticket, which says he doesn't want to do it, not
that he doesn't have time to do it, and because I know that particular
person and his attitude.

>
>>> Thus I think it would be better to reduce this to a warning for the
>>> time being and maybe add a FF_API_* changing it to an error after
>>> the usual deprecation period.
>>>
>>
>> I do not agree that it should be a warning. As outlined in the commit
>> message and this thread, there are serious flaws with frame threading
>> and hwaccel.
>
> I'm fine with it being an error, but since it is an API change, it
> should follow the usual deprecation period to allow downstream users
> time to fix it. Meanwhile it can be a warning so that people notice
> the problem.

Its fundamentally broken, and making it a warning would re-introduce
known crashes. So no.