avplayback(1) avplayback(1)
NAME
avplayback - playback uncompressed video and audio in synchronization
SYNOPSIS
avplayback -[a# b# d# h r# t%s v vlancmdfile A B D V] <filename>
PARAMETERS
-a <audio format>
specifies the file format of the audio data:
1 = no audio
2 = QuickTime
3 = AIFC
If audio output is not disabled with -a1 an embedded audio track
will be played if it exists. If an embedded track does not exist
then a file with the suffix .aifc will be opened for playback.
-b <buffer size>
allows you to specify the maximum number of buffer elements to be
allocated. By default, 4 buffers are used, but the value can be
adjusted for I/O load balancing. The maximum number of buffers which
can be allocated is limited by the amount of available physical
memory in the system.
-d <video device number>
specifies the video device to be used (as reported by vlinfo). This
need not be specified unless you have more than one video device in
your system; it defaults to 0, i.e. the first device found.
-h prints a usage message giving a summary of available flags.
-r <scatter gather>
specifies the number of images to simultaneously read from disk
using readv(2)
-t </dev/ttyd#>
specify the tty device port for serial RS422 V-LAN control
-v instructs the program to parse the specified file for V-LAN commands
and to issue them immediately.
-A abort if any image is dropped (when a VL sequence lost event is
generated).
-B calculates the video disk I/O performance and prints the results
after the last image is output.
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avplayback(1) avplayback(1)
-V enables verbose mode and prints the values of parameters used to
setup the hardware for audio and video transfers.
<filename> specifies the name of the file to read. If the -a2 option
is chosen audio data will be in the separate file
filename.aifc. If the -a3 option is chosen audio data will
be embedded in the QuickTime file filename.
DESCRIPTION
The utility avplayback uses the Digital Media libraries to output a
sequence of video images and audio samples from various Silicon Graphics
digital media devices. As of this release audio data originally captured
with avcapture in a separate AIFC file played in sync with the video
using the -a3 option. If the audio and video hardware are locked to a
common external reference signal the audio and video data are guaranteed
to remain synchronized. If either device drops data synchronization will
be recalibrated. Visual or audio artifacts may be noticed at this time.
avplayback is best suited to playback large volumes of audio and video
data in realtime. This is possible if a striped logical volume disk
array of sufficient size and configuration is used with the XFS file
system. Before copying data to disk from an external source test the
performance of the array using the tool diskperf. It may be necessary to
reconfigure the array with diskalign before realtime playback can be
achieved.
See /usr/share/src/dmedia/movie for details on how to create and edit
QuickTime files using the SGI movie library.
All of the video control parameters including output timing and data
format are automatically set by the tool. If audio output is enabled
default audio device is used. The audio control parameters can be
adjusted with apanel.
The -v option specifies a text file containing V-LAN edit commands.
Robust error checking is not performed, therefore, unpredictable behavior
should be expected if invalid V-LAN commands are issued or if the
commands are issued in the wrong order. Permissions and ownership of the
command file must be properly set. If V-LAN control is chosen and the CO
(Coincidence On) and SC (Set Coincidence) commands are issued the GPI
output of the video device must be connected to the V-LAN receiver in
order to accurately initiate the data transfer. This option should be
used in conjunction with the -t flag. A special cable must be
constructed for the trigger output. See Appendix A of the DIVO XIO Board
Owner's Guide for details.
SEE ALSO
avcapture(1), diskalign(1), diskperf(1), memtovid(1), orion(1),
vidtomen(1)
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