The tpad filter is problematic on the variable-framerate webcam files,
and the result can end up being hangs (or, at least, very slow
processing) in the compositing.
Move the tpad filter to the compositing process where it can run after
the fps filter has converted the video to constant framerate. It still
needs to run before the start trimming, so switch to using the trim
filter rather than the fps filter's start_pts feature.
The tpad filter is problematic on the variable-framerate webcam files,
and the result can end up being hangs (or, at least, very slow
processing) in the compositing.
Move the tpad filter to the compositing process where it can run after
the fps filter has converted the video to constant framerate. It still
needs to run before the start trimming, so switch to using the trim
filter rather than the fps filter's start_pts feature.
Even with the filter changes made, there's still some cases where
filter chain hangs can result from filter reconfigurations. To solve the
issue completely, I have split out pre-processing video files to
separate ffmpeg processes, so that the filter chain for compositing will
not ever be reconfigured.
Each input video now has a separate ffmpeg process run for it which
does the scaling, padding, and video extending steps. To avoid issues
with disk space usage and extra cpu usage or quality loss, the output
from these separate processes is sent to the compositing ffmpeg process
as uncompressed video in a pipe. To simplify the setup, named pipes
(special files) are used rather than setting up pipes in the ruby code
programmatically.
The extra ffmpeg processes are configured to log to files, and when
complete their log output is copied to the recording processing log.
Processes are joined to ensure zombie processes are not created, and
the return codes of all the processes are checked so errors can be
detected.
Due to the overhead of transferring video through pipes, this might
be a bit slower than the 2.4 recording processing - but on the other
hand, some of the video decoding and scaling happens in parallel, so it
might balance out.
Even with the filter changes made, there's still some cases where
filter chain hangs can result from filter reconfigurations. To solve the
issue completely, I have split out pre-processing video files to
separate ffmpeg processes, so that the filter chain for compositing will
not ever be reconfigured.
Each input video now has a separate ffmpeg process run for it which
does the scaling, padding, and video extending steps. To avoid issues
with disk space usage and extra cpu usage or quality loss, the output
from these separate processes is sent to the compositing ffmpeg process
as uncompressed video in a pipe. To simplify the setup, named pipes
(special files) are used rather than setting up pipes in the ruby code
programmatically.
The extra ffmpeg processes are configured to log to files, and when
complete their log output is copied to the recording processing log.
Processes are joined to ensure zombie processes are not created, and
the return codes of all the processes are checked so errors can be
detected.
Due to the overhead of transferring video through pipes, this might
be a bit slower than the 2.4 recording processing - but on the other
hand, some of the video decoding and scaling happens in parallel, so it
might balance out.
