VNR 100 • Reference Information
37
Working with Video and Audio Streams
When recording video content along with associated audio, the Start and Finish times
for the each of the different recorded file types can differ by a small amount. Usually, the
video file will be slightly longer and its start and end times will overlap the other files in the
recording.
The times specified in the gcode utility must take this difference into account or
synchronization of the content in the converted files will be lost, most noticeable in loss of lip
sync between video and audio content.
When using the gcode utility to convert two files, the start and end times set for each file
conversion must be the same and must overlap.
When setting the start time for a conversion, check the start times for each of the files that
are to be converted and use the start time of the file that is last to start up, that is the latest
start time.
For the end time, use a similar process but use the end time of the file that is first to stop,
that is the earliest end time.
Example 1:
VideoStartTime=17:43:13.84
Video Finish Time = 17:49:11.36
Video file
Audio Start Time = 17:45:35.41
Audio Finish Time = 17:49:11.20
Audio file
In the above diagram, the start and end times of the video and audio files are different.
NOTE:
The difference in start time is exaggerated to illustrate this point. In practice, the
difference will be much smaller.
To create the correct number of video frames and a .WVA file of the correct length you must
specify the correct Start and Finish times within the gcode command line.
For this example a Start time of 17:45:35.50 (after both the audio and video files have
started) and a Finish time of 17:49:11.00 (before either file finishes) would be appropriate.
This results in video and audio files of the same length being created. These files can be
used with third-party video editing software to produce a correctly lip-synced file.
You will need two separate commands, the first to generate the video file and the second to
generate the audio file:
./gcode -t -o /home/matrix_rec/Targa -s 17:45:35.50
-f 17:49:11.00 -i /home/matrix_rec/Storage/SAC_Test/
Dave_Gilmour_Dimming_of_the_Day_620027.0.0_r0_s0.rec
./gcode -o /home/matrix_rec/Targa -s 17:45:35.50 -f 17:49:11.00 -i /
home/matrix_rec/Storage/SAC_Test/Dave_Gilmour_Dimming_of_the_Day_620027.
A0.0_r0_s0.rec
•
The first command uses a video file to produce targa files (
-t
).
•
The second command uses an audio file (
.A0
) to produce a WAV file.
•
Both the audio and video files are generated from the same start time (
17:45:35.50
) to
the same finish time (
17:49:11.00
).