Antex Electronics StudioCard AV Pro, StudioCard 2000, & SC-22 - Manual (Page 84)

U s i n g t h e S t u d i o C a r d w i t h V i d e o C a p t u r e & D i s p l a y B o a r d s C h a p t e r 4
Antex Electronics Corporation Antex StudioCard 4-7
Using the
StudioCard
with Video
Capture &
Display
Boards
Audio sampling on most audio cards is generated by a crystal
oscillator. Since this oscillator has no reference to the
oscillator on the video board used to generate frames of video,
the audio and video can drift out of synchronization. This is the
equivalent of setting two watches to exactly the same time and
watching them slowly drift apart. The StudioCard has the
unique ability to lock its internal oscillator to timing signals
provided by most video capture and display boards. When the
StudioCard is referenced to this video timing signal it is
impossible for audio to drift out of synchronization with video.
This is extremely important when long video clips are used.
It is important to note that one of the locking methods listed
below must be in place for both capture and playback of the
source audio to insure synchronization. Audio digitally input to
the StudioCard (S/PDIF or AES/EBU) will not be locked to the
video as the sample clock used to digitize the audio was not
locked to the video sample clock.
Synchronizing the
StudioCard
Described in this section are two methods of synchronizing the
StudioCard to the PVR, Truevision, Intergraph, Matrox, and
other video capture boards:
Master 27 MHz clock lock (PVR only)
Horizontal sync lock (all video boards)