Record Movie Using Mask - Single Pass

Record Movie Using Mask - Single Pass

This option is a variant on [R Record movie - single pass]. It provides the same basic abilities with the additional functionality of providing ALU operations during the recording process.

It records with either manual or computer controlled synchronisation in a single pass. If the requested frame rate exceeds that the computer is capable of, then frames will be dropped and the maximum achievable rate will be used.

DigImage movie files normally have a .MOV extension and consist of a sequence of images stored in a single file. They are accessed as a direct access binary file with one byte per record. The file format consists of four blocks of header information followed by the raw image data:

GeneralHeader 256 bytes

                   Contains general information

HistoryHeader 256 bytes

                   Contains information about the file history

MovieHeader 1024 bytes

                   Contains information about the images and movie sequence

MovieFrameTable 32768 bytes

                   Stores pointers to each frame (maximum of 2048) in the
                   movie

For complete details on each of these headers, refer to DigImage\Include\Headers.INC.

Name of movie to be created (.MOV default extension) ?

The images acquired as part of the movie will be stored in the file specified here. For full details of the format of this file, refer to DigImage\Include\Headers.INC.

Set recording window using which buffer ?

Only the region of the image falling within a user specified window will be recorded. The smaller this window is, the closer the samples may be together without loosing data. The buffer specified here will be displayed while the window is being specified.

Window Selection: Region to record in movie

The Window Selection submenu is produced to allow the desired region to be selected. For further information on the use of windows, refer the [H Help] within the Window Selection submenu.

Horizontal step ?

By sampling the image on a coarser grid the frame rate of the recording may be increased. This entry specifies the horizontal spacing between samples to be included in the movie image.

Vertical step ?

This entry specifies the vertical spacing between the samples to be included in the movie image.

Spacing between images ?

This entry specifies the temporal sampling frequency or frame rate of the movie. If the requested frequency is too high (spacing too small), then it will not be possible to maintain the required interval between images. If the spacing is not a multiple of the spacing between images for the video source (1/25 or 1/30s for PAL or NTSC), then the sample spacing used will not be constant but will be chosen so as to best approximate the requested spacing.

Duration of movie ?

The duration of the movie is fixed by this entry. The duration is converted into the number of samples to be recorded. The duration of the movie will be adhered to (as closely as possible) even if DigImage is not able to maintain the requested frame rate.

Use which buffer as a mask ? Must be onboard buffer and not buffer 0 (-1 for input buffer)

This option specifies the buffer to be presented to the "B" input arm of the ALU. If -1 is specified, then the buffer being acquired will be its own mask, even if an extended memory buffer is being acquired. If another value is given, then it must correspond to an onboard buffer; the same buffer will be used for every image in the sequence (though the buffer's contents may be changed by acquiring to it).

ALU Operations: This input specifies the ALU operation to be used during the acquisition process. The ALU operations are divided into logical operations and two classes of arithmetic operations. The two classes of arithmetic operations vary in how the CARRYIN register on the frame grabber card is set. A list of the 48 operations is given below:

      Logical         Arithmetic              with carry
      0  nA           16 A                    32 A + 1
      1  n(A or B)    17 A or B               33 (A or B) + 1
      2  nA and b     18 A or nB              34 (A or nB) + 1
      3  0            19 -1                   35 zero
      4  n(A and B)   20 A + (A and nB)       36 A+(A and nB)+1
      5  nB           21 (A or B)+(A and nB)  37 (A or B)+(A and nB)+1
      6  A xor B      22 A - B - 1            38 A - B
      7  A and nB     23 (A or nB) - 1        39 A and nB
      8  nA           24 A + (A and B)        40 A+(A and B)+1
      9  n(A xor B)   25 A + B                 41 A + B + 1
      10 B            26 (A or nB)+(A and B)  42 (A or nB)+(A and B)+1
      11 A and B      27 (A and B) - 1        43 A and B
      12 1            28 A + A                44 A + A + 1
      13 A or nB      29 (A or B) + A         45 (A or B)+A+1
      14 A or B       30 (A or nB) + A        46 (A or nB)+A+1
      15 A            31 A - 1                47 A

Note that nA and nB are the logical compliments of A and B, respectively. Addition operations (+) produce results between 0 and 511 as expected from adding two eight bit values. The subtraction operations (22 and 38) produce values between 256 and 511 for positive results, and between 0 and 255 for negative results.

Select Input Look Up Table The digitized eight bit signal produced by the A/D converter is applied to input "A" via input look up table (ILUT). A number of simple manipulations may be performed using this table. Details on those available are given by the 'H' Help option within the Select Input Look Up Table submenu.

Select Result Look Up Table The nine bit signal output from the ALU must be mapped onto eight intensity bits. This is achieved by passing the ALU output through the 512 elements of the Result Look Up Table (RLUT), each element containing an eight bit value. The mapping may perform simple arithmetic operations in its own right. Details on the RLUTs available are given by the 'H' Help option within the Select Result Look Up Table submenu.

Manual or Computer synchronisation ?

The start point of the movie may be provided by either manual (<M>) synchronisation with the video, or by direct computer control (<C>).

{If computer synchronisation}

Start time (offset from current position) ?

The movie recording will start at the specified offset from the current position of the VTR. If positive the movie will start after this point, while negative will make the movie start before this point.

{If computer synchronisation}

On completion Reposition video tape or Leave it where it is ?

Once the acquisition has been completed, the video tape may be either repositioned to its initial location (<R>), or simply left where it is. In both cases the location may be obtained through the !!V system variable.

{If manual synchronisation}

Start recording or Quit ?

This message will be produced when DigImage is ready to start recording the movie if manual synchronisation is being used.

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Stuart Dalziel, last page update: 19 February 1996