In some cases, we get DRAW_END events for pencil shapes from the
html5 client that have no dataPoints. The only thing we can really
do here is detect the issue and ignore the shape.

In some cases, this may result in the shape's intermediate drawing
updates being shown, but it'll disappear when the end event happens.

The checks for 0 numerator or denominator were failing due to
type mismatch

The archive_dir can by the raw recording directory in some recording
formats - including, hopefully, presentation at some point (to avoid the
extra copy)

The previous calculation used the video size in pixels, which might lead
to stretched/squashed videos in rare cases where the video has non-square
pixels. The new calculation is correct for all video sizes.

The video_info function returns the start time already in milliseconds,
so compare against 1ms instead of 1/1000.

The ffprobe command in ffmpeg 4.0 now omits the aspect ratio fields in the
json output when indeterminate, instead of returning an invalid value with
0 in the numerator or denominator. Handle this correctly.

Since the update to the newer red5, seeking in flv files (webcams in
particular are noticable) has been broken, resulting in cameras
appearing to "hang" any time there is a cut in the generated video -
which happens when start/stop button is pushed, or when cameras are
added or removed.

We can detect the problematic video files because the timestamp of the
first frame is large (old red5 versions always set first frame
timestamp to 0.001 seconds). If we see a file like this, having ffmpeg
remux the file - rewriting the timestamps and index - works around the
problem.

Due to improvements in the recording scripts, most of the stuff the sanity
script was checking for is no longer needed (missing/corrupt video files
are handled by the processing scripts). The version of this script in
master has been cleaned up so that the only things it does are:

- Check that the events.xml exists and is properly formatted xml
- Rebuild flv files from red5 .flv.ser/.flv.info files

The script from master is compatible with the 2.0 code, so just use it
as-is.

This fixes a problem where following the recent red5 upgrade in 2.0 branch,
an flv file is never written for webcam streams where no frames were
received, despite there being recording events.

This improves the quality of portrait documents, before they were
1200px when landscape documents got 1600px.

Switching to scaling to a square means that we can use the "-scale-to"
option on pdftocaio, which means that it generates images directly
at the desired size. This can save quite a bit of time (and memory)
if a document was uploaded with extremely large page size.

There's some cases where you can get 0-duration recordings due to
recording event placement (e.g. a single recording event is the last
event in the events.xml). Detect these cases, and treat them like
no recording marks in the archive script (it will stop the recording
from being automatically processed).

I've also adjusted the sanity script to detect these cases and error
out. The recording processing scripts cannot handle 0-length recordings,
you have to manually edit the events. I've added a message to the
sanity log about this.

I forgot to include the 'K' multiplier on the bitrate values, so they
were all 1000 times too low.

Generates a single .ogg file containing the meeting audio

In some cases (due to network issues), the webcam video can be shorter
than the time between the start/stop events. Pad the input video with a
blank video to make sure that there's input to the video tiling filters,
to fix a problem where the video won't render correctly with ffmpeg v3.4
and later.

In some cases when there is a slight mismatch between audio file
duration and event timestamp difference, and we have a record
status or chapter break event in a certain location, it could
trigger a seek past the end of an audio file. Detect this
condition and just render silence instead.

Also adjust the thresholds for the audio length scaling - they
were being triggered on short recordings that should be correct.

Red5 sometimes writes webcam video files with a large offset in the
video frame offsets, sometimes up to 30 or even 60 seconds. However,
the start event in the events.xml file corresponds to the time at
which red5 received the first keyframe (recorded frame) in the video.

The end result is that the video will sometimes appear to be
delayed (out of sync) in the processed recording.

The correction is simple: We're already reading video metadata,
including the timestamp of the first frame, so we just have to apply
a correction during video processing to undo the frame timestamp
offsets in the video file.

If you're inserting at position 0 (and there was no previous deleted text
from that position), you can't use the timestamp from the previous character
position, since there's no previous character. Use the timestamp of the
following character instead.

In some unusual cases, the recording start can be the last event in the
events file, or at least have the same timestamp as such.

Add some code to check the array bounds and break if needed, so we
don't check the timestamp on the (non-existant) event after the last
event.