[FFmpeg-user] metadata from concat list not working

[Paul B Mahol]

On 9/30/19, Goran Obal <obal.goran at gmail.com> wrote:
> Hi everyone,
>
> I apologize for spamming... I just saw that it is in fact working for me
> when I do it with pictures, I was just using such examples that the text
> was not visible. Sorry.
> So, yes, it seems I don't understand what is different when I create video
> from a bunch of pictures and when I use filter_complex to create video from
> audio files and try to write text over it... I assume that the "picture
> way" is then packet and the "audio visualization filter way" is then a
> stream.
> So I think my question should be: Can I inject metadata to a stream?

Yes with ametadata and metadata filters, read their documentation.
Note that drawtext filter command you used use only frame metadata,
and frame metadata
can be added/removed/changed by mentioned filters above.
The concat demuxer can not set/remove/change frame metadata.
Also frame metadata is per each frame and can obviously disappear and
appear at any time.
AFAIK there is no way for filters to know stream metadata, so your
approach to draw text is wrong.

Stream metadata is static per stream and never changes.
Frame metadata can be available in each filtered frame.

>
> Best regards.
> Goran
>
>
> On Mon, Sep 30, 2019 at 10:47 AM Goran Obal <obal.goran at gmail.com> wrote:
>
>> Hi Nicolas,
>>
>> I am trying to understand what you meant, but unfortunately I don't get
>> it.
>> I am still a beginner with video filters of ffmpeg and what I read in the
>> documentation for stream metadata and packet metadata didn't help me to
>> see
>> what I was confusing.
>>
>> What I would like to understand is why does it work for the weather
>> station (the link in my first email) and why is the same logic accepted
>> here:
>> https://superuser.com/questions/1336844/is-it-possible-to-burn-a-filename-watermark-in-the-corner-of-a-concatenated-imag
>> as
>> an answer.
>> When I try to reproduce what the weather station has or what this second
>> link describes, I don't get the text in the video. The weather station
>> even
>> posted its video and there you can clearly see that the metadata
>> from custom-list.txt is displayed on bottom-left of the video
>> <https://www.youtube.com/watch?v=nq4ZGtLOw6Q>.
>>
>> If it worked for them, why doesn't it work when I try to reproduce it?
>>
>> Best regards.
>> Goran
>>
>>
>> On Sun, Sep 29, 2019 at 7:39 PM Nicolas George <george at nsup.org> wrote:
>>
>>> Goran Obal (12019-09-29):
>>> > Somehow this is not working for me and I don't understand why. My video
>>> > displays text "blah", which tells me that ffmpeg can't find the
>>> metadata...
>>>
>>> I suspect you are confusing stream metadata and packet metadata.
>>>
>>> Regards,
>>>
>>> --
>>>   Nicolas George
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>>
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