[FFmpeg-devel] [PATCH 2/3] avcodec/h264: error out on ff_h264_pred_weight_table() only if strict spec compliance is requested

[James Almer]

On 4/13/2019 10:28 AM, James Almer wrote:
> On 4/13/2019 5:44 AM, Carl Eugen Hoyos wrote:
>> 2019-04-10 21:47 GMT+02:00, Carl Eugen Hoyos <ceffmpeg at gmail.com>:
>>> 2019-04-09 20:32 GMT+02:00, James Almer <jamrial at gmail.com>:
>>>> Fixes ticket #7174.
>>>>
>>>> Signed-off-by: James Almer <jamrial at gmail.com>
>>>> ---
>>>> This makes what's essentially a non spec compliant
>>>> stream decodable again with no visual artifacts, and
>>>> without reintroducing the risk of overflows.
>>>
>>> Your patch leads to bit-exact output with the reference
>>> decoder and old FFmpeg.
>>
>> This is true for the original sample, the new sample
>> zNqp.h264 has bit-exact output with old FFmpeg
>> but not with your patch.
> 
> Where can i get this sample? Perhaps clipping the bogus value will make
> it bitexact.
> 
> It would be nice to know what the reference decoder does, for that
> matter. If it's bothering like us to check and handle this out of spec
> values, or if they do like we used to and just pass them through.

Found it and tested the above, and with clipping it still doesn't seem
to be bitexact with old ffmpeg.