[FFmpeg-user] Use processed filename as draw text after tmix, in one pass?

[Steven Kan]

> Thanks! This works, and I agree that it’s better than using the filename:
> 
> ffmpeg -pattern_type glob -i '*.jpg' -vf "drawtext=text='%{metadata\\:DateTimeOriginal}': fontfile=/System/Library/Fonts/Helvetica.ttc:fontcolor=white: fontsize=48: x=(w-text_w)*0.01: y=(h-text_h)*0.98" -y CombLapseWithTimeStamp.mp4
> 
> I can now add tmix after drawtext:
> 
> ffmpeg -pattern_type glob -i '*.jpg' -vf "drawtext=text='%{metadata\\:DateTimeOriginal}': fontfile=/System/Library/Fonts/Helvetica.ttc:fontcolor=white: fontsize=48: x=(w-text_w)*0.01: y=(h-text_h)*0.98, tmix=frames=10:weights='1'" -y CombLapseWithTimeStampAndTmix.mp4
> 
> And it renders, but the timestamps get blended.
> 
> Can I use “split” to make one stream of images from which I can extract the timestamp, and then another stream for tmix, and then overlay the timestamp after tmix? How would I sync up the two streams, since tmix would be N frames shorter than the original?

Hmmm. 

This:

https://youtu.be/-NB1JzR5aCQ

is the result of:

ffmpeg -pattern_type glob -i '*.jpg' -vf "split [tmp][main]; [tmp] crop=iw:ih*0.05:0:ih*0.95, drawtext=text='%{metadata\\:DateTimeOriginal}': fontfile=/System/Library/Fonts/Helvetica.ttc:fontcolor=white: fontsize=72: x=(w-text_w)*0.01: y=(h-text_h)*0.01 [text]; [main] tmix=frames=10:weights='1' [blend]; [blend][text] overlay=0:H*0.95" -y CombLapseWithTimeStampAndTmixSplit.mp4

which approximates the result I'm trying to achieve, but it's cheating, because it's making a separate stream of the bottom 5% of the video with the drawtext overlay, and then overlaying that on top of the blended frames. It appears to work only because there's nothing much happening in the bottom half of the frames.  If there were any significant bee activity in the bottom 5% it would be apparent that that section is not getting tmixed.

Can anyone help me construct a filter chain that will overlay the internal timestamp in an arbitrary position on top of the blended frames, after tmix has been applied?