[gst-devel] textoverlay and dynamic text - to subtitle or not and if so how?

[HaroldJRoth]

Andoni Morales wrote:
> 
> 2010/11/9 HaroldJRoth <dlafferty at gmail.com>:
>>
>>
>> Andoni Morales wrote:
>>>
>>> 2010/11/9 HaroldJRoth <dlafferty at gmail.com>:
>>>>
>>>> Can textoverlay be used to apply dynamically generated text to a frame?
>>>>
>>>
>>> ...
>>>
>>> You could also use the 'textrender' element, which support plain text
>>> and pango markup.
>>>
>>> andoni
>>>
>>>
>>
>> Two issues:  'textrender' doesn't mux text to another video stream.
>>  Second,
>> 'textrender' doesn't allow me to sync my text to frame TIMESTAMP data.  I
>> think textrender on its own is more appropriate for generating text only
>> frames from a textparse element.
> Textrender, which outputs an image with an alpha channel, is usually
> used in combination with videomixer, which mixes your video stream
> with the text image and sync them, so it's exactly what you are
> looking for. IIRC playbin2 uses it to render the subtitles.
> 
> Andoni
> 

Unfortunately, it's not merging text with that's the issue.  The difficulty
is specifying the input to the textrender.  It looks like I need to generate
application/x-subtitles data for the frames that I wish to write text to. 
My goal is to cross reference timestamp data with other metadata and write
this to the frame.  I can't update the text directly from my appsrc plugin,
because it will fall out of sink with the frame due to delays in the
decodebin2 plugin between any text overlay and the appsrc.  

Do you have any suggestions on there to look for details on generating the
application/x-subtitles data used by a subparse?
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