Basler ace acA1920-155, Руководство пользователя, Страница: 313 / 326

AW00123404000 Features
Basler ace USB 3.0 303
8.18.4 Retrieving Data Chunks
When the chunk mode is active and data chunks are enabled, the selected data chunks are
appended to each acquired image when the image is transferred to the host PC (see Section 8.18.1
on
page 295 ), creating a set of chunks.
The set of chunks includes chunk 1 with the image data ("image data payload") and related
supplementary data (chunk ID and length of the image data payload), followed by the selected data
chunks, each one consisting of the chunk payload and supplementary data.
The PayloadSize parameter value for the device (i.e. for the camera) indicates the calculated
maximum size ("maximum buffer size") that can be expected to occur for a set of chunks. The
calculated maximum size is derived from the current camera parameter settings (ROI size, pixel
format, selected data chunks, etc.).
The actual size of a set of chunks as received by the PC ("grab result") can be read form the
PayloadSize value for the grab result . The actual size will be equal to or smaller than the
calculated maximum size.
A set of chunks (chunks one through N) is illustrated in Figure 112 . The example assumes that the
CRC Checksum chunk was enabled.
Fig. 112: Example of a Set of Chunks Related to One Image Acquisition
Make sure all camera parameters are set as desired before reading the
PayloadSize parameter value.
Chunk
1
(Image data payload)
Chunk
1
(ID)
Chunk
N
CRC
Chunk
1
(Length)
...
Chunk
2
(Length)
Chunk
N
(Length)
Chunk
N
(ID)
Chunk
2
(ID)
Chunk
2
(Payload)
32 bit 32 bit 32 bit 32 bit 32 bit 32 bit Length Length Length
Chunk 1 Chunk 2 Chunk N
Actual payload size of the grab result