Browse Prior Art Database

Method for Synchronized Active Video Capture and Playback with Field Memory

IP.com Disclosure Number: IPCOM000117164D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 124K

Publishing Venue

IBM

Related People

Potu, B: AUTHOR [+2]

Abstract

A typical video capture and playback adapter performs digitization of analog video input into its components with a video decoder for further processing such as compression and storage. It also performs playback operation with the decompressed video data. The compression and decompression operations can be performed by a hardware video codec or by the main processor itself in software. The terms compression and capture operation, decompression and playback operation are used interchangeably in this disclosure. A storage buffer is required for both the capture and playback operations as illustrated in Fig. 1.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Method for Synchronized Active Video Capture and Playback with Field
Memory

      A typical video capture and playback adapter performs
digitization of analog video input into its components with a video
decoder for further processing such as compression and storage.  It
also performs playback operation with the decompressed video data.
The compression and decompression operations can be performed by a
hardware video codec or by the main processor itself in software.
The terms compression and capture operation, decompression and
playback operation are used interchangeably in this disclosure.  A
storage buffer is required for both the capture and playback
operations as illustrated in Fig. 1.

      The storage buffer needs to contain only the digital video data
that is decoded from the active video signal.  Various parameters
such as field capture or playback rate, the size of the image should
be selectable.  The buffer also needs to be synchronized with the
video timing so that it does not contain parts of different fields
during compression of a field.  During playback, similar features are
required to achieve a tear-free display of video.

      The solution is to use a field memory with a configuration
register for synchronized capture and playback as illustrated in
Fig. 2.  The configuration register has four bits to  control the
operation of the field memory.  The register is programmable and can
be changed for capture and playback operations independently.  The
configuration bit fields specify various modes of operation.  They
represent the following parameters for a capture or playback
operation (Fig. 2).
  Fr/F  --  frame or field
  E/O   --  even or odd field, if F (field) is selected
  Fu/Ci --  full size or CIF (common intermediate format) size image
  C/D   --  compression/capture or decompression/playback
  N/P   --  NTSC or PAL/SECAM source
  S/Co  --  single or continuous mode

The configuration bits completely control the video data that gets
stored from the video I/O bus during compression and the video data
that is read out from the field memory to video I/O bus during
decompression.

      During a capture operation, only active video part is stored in
the field memory using a counter.  The active video part in an NTSC
signal corresponds to 640 pixels/line X 240 lines/field and 768
pixels/line X 288 lines/field for PAL or SECAM signals.  The video
timing signals, horizontal sync (HS) and vertical sync (VS) represent
end of filed and end of line signals for a real-time video source as
illustrated in Fig. 3.  The active video starts after 11 inactive
lines in NTSC and 16 inactive lines in PAL or SECAM signal.  The
timing pulses and configuration bits are used...