Data

Files associated with data buffers.

Name following this syntax: <Zero-based buffer index>

Purpose

Data files represent buffers. They are as many files as buffers in the frame store. The buffers are entitled to contain data coming from the board by DMA.

Attributes

The data files are readable and writable.

Frame Store

The frame store is the collection of buffers entitled to receive the data coming from one Picolo U4 H.264 PCI-104 capture channel. Three types of Picolo U4 H.264 PCI-104 constituents feature a frame store: the visual encoder, the visual formatter and the audio encoder.

The frame store buffers are allocated by the Virtual File System driver in virtual memory. The size of the frame store and buffers is set by the user application through the configuration files.

At system initialization, the frame store contains no buffers, and there are no files in the corresponding data directory. The buffers are allocated and the files created, when the user application sets the appropriate configuration settings.

When the number of filled buffers reaches BufferCount, the acquisition is suspended until the user release some buffer(s).

The buffers are passed to the hardware for DMA operations.

Read

Data files can be read at anytime, as long as they exist. When the application reads a data file, the Virtual File System driver provides the buffer's content, without delay.

Mmap

Data files can be mapped in application's memory, as long as they exist, giving direct access to the buffer's content.

Write

Writing in a data file causes the buffer's content to be updated accordingly, without delay.

Delete

Deleting a data file is allowed, but it effectively does not delete the file. Instead, the buffer is disposed of (as per writing the Dispose element in metadata.xml) and the corresponding metadata is updated accordingly.

Synchronization

Several applications can access the files simultaneously. When doing so, it is the application's responsibility to synchronize the file accesses.