Virtual File System Driver Overview
The Virtual File System driver for Picolo U4 H.264 PCI-104 is a memory-based file system driver. Each board appears as a file system populated with files organized as a directory tree. These files are managed using standard file management functions of the operating system.
The Virtual File System driver supports the following board features:
- Audio inputs
- Video inputs
- Input lines
- Output lines
- Audio sampling rates
- Watchdog
- Pass-through selector
The top-level of the directory structure looks as follows:
Refer to the corresponding topic in File System Structure for more details.
You will see the complete virtual file system for this device. The command and result are displayed hereafter:
$ ls -g
total 0
drwxrwxrwx 6 root 0 2009-12-16 12:09 audio
-r--r--r-- 1 root 1288 2009-12-16 12:09 config.dtd
-rw-rw-rw- 1 root 0 2009-12-16 12:09 config.xml
-r--r--r-- 1 root 4377 2009-12-16 12:09 exceptions.dtd
-rw-rw-rw- 1 root 0 2009-12-16 12:09 exceptions.xml
drwxrwxrwx 6 root 0 2009-12-16 12:09 inputlines
drwxrwxrwx 6 root 0 2009-12-16 12:09 outputlines
drwxrwxrwx 2 root 0 2009-12-16 12:09 passthroughselector
drwxrwxrwx 6 root 0 2009-12-16 12:09 visual
drwxrwxrwx 2 root 0 2009-12-16 12:09 watchdog
The data acquired by the board are provided as binary files containing raw data:
- Compressed video data
- Uncompressed video data
- Audio data
Each data file is associated with a metadata file that contains a plain-text XML description of the captured data.
The board is controlled through plain-text XML files:
- Configuration settings are made through Configuration files.
- Events are reported into Events files.
- Abnormal events and errors are reported into Exceptions files.
Every XML file is associated with a Document Type Definition (DTD) file that validates the syntax of the XML file.
There are three types of files on the Picolo H.264 file system:
- Data files
- Data files are binary files.
- Each file corresponds to one memory buffer.
- The buffers contain the data delivered by the card, without any addition or modification by the driver.
- XML files
- XML files are text files.
- They follow the XML syntax.
- They contain configuration, event, metadata, or exception data.
- DTD files
- DTD files are text files.
- They contain a set of markup declarations that define a particular type of XML document.
- They contain the validation rules for the card's XML files.