Dot file element properties "atomicity"? Queue level time and buffers don't match

[Michiel Konstapel]

On 30-06-2021 16:18, Arun Raghavan wrote:
> On Wed, 30 Jun 2021, at 9:39 AM, Nicolas Dufresne via gstreamer-devel wrote:
>> Le mercredi 30 juin 2021 à 10:09 +0200, Michiel Konstapel via gstreamer-devel a
>> écrit :
>>> I'm seeing some "impossible" values in my debug dot files, namely queues
>>> with current-level-buffers=1 and current-level-time=1_720_000_000, in a
>>> pipeline where every video buffer should be 40 ms (25 fps):
>>>
>>>
>>> GstQueue
>>> queue:video2-preview
>>> [>]
>>> current-level-buffers=1
>>> current-level-bytes=8294400
>>> current-level-time=1720000000
>>> max-size-buffers=0
>>> max-size-bytes=0
>>>
>>> Are the property values shown in a dot file an "atomic" snapshot or is
>>> it possible it first read the current time, then a load of buffers got
>>> taken out, and then the current-level-buffers was read?
>>
>> No, they are not atomic. This is fetch independently from a running pipeline.
>>
>>>
>>> Then I still can't explain the picture, because the max-size-time of the
>>> queue is the default one second, so I don't understand how 1.7 seconds
>>> worth of buffers got in there.
>>
>> I confirm the result does not seems logical, you'd need 43 buffers, which is too
>> big of a difference. That being said, there is too little information here to
>> help you investigate.
> 
> Possibly related: https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/684
> 
> -- Arun

Thanks, that's good to know! I'm not sure I can pin my case on that bug, 
though, I think I've always seen this when the branch had been running 
for a while. I'll keep an eye out!
Michiel