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Re: Video narration

From: Paul Garlick
Subject: Re: Video narration
Date: Mon, 06 May 2019 21:34:40 +0100

Hi Ricardo,

> Are you saying you want to take snapshots in larger intervals and pad
> the intermediate frames with duplicates of previous frames?

Thank you for writing the snap! procedure.  It is writing the output as

The problem we ran into was to do with the timing.  If you go back in
this thread you will see the history.  

In order to produce .webm files that are compatible with the Firefox
browser it is necessary to eliminate gaps in the audio streams.  ffmpeg
can do this automatically using the 'apad' filter.  However, it will
truncate the audio stream if the video stream is shorter in duration
than the audio stream.  

So, in preparing the cli session files we need to be able to accurately
set the duration of the last 'sleep' command.  Since we know the frame
rate (25 fps) it is straightforward to calculate the number of repeated
frames we need for any given duration.  This is the job of the new
'repeat' procedure.  

In this way we effectively replace the timer with a counter.

The session files now need to be checked to tune the sleep commands to
synchronize with the audio stream.  I will be able to look at 02-daily-
use1 again tomorrow.

Best regards,


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