Forward Error Correction with a Cauchy MDS block erasure codec is used to prevent block loss. This can make the UDP transmission more robust particularly over WiFi links.
The distant SDRangel instance to which the data stream is sent is controlled via its REST API using a separate control software for example [SDRangelcli](https://github.com/f4exb/sdrangelcli)
The sample size used in the I/Q stream is the Rx sample size of the local instance. Possible conversion takes place in the distant Remote source channel plugin to match the Rx sample size of the distant instance. Best performace is obtained when both instances use the same sample size.
The plugin will be built only if the [CM256cc library](https://github.com/f4exb/cm256cc) is installed in your system. For CM256cc library you will have to specify the include and library paths on the cmake command line. Say if you install cm256cc in `/opt/install/cm256cc` you will have to add `-DCM256CC_DIR=/opt/install/cm256cc` to the cmake commands.
This is the remote instance baseband sample rate. It can be a power of two multiple of the stream sample rate (2) but it will not work for other values.
This sets the minimum delay between transmission of an UDP block (send datagram) and the next. This allows throttling of the UDP transmission that is otherwise uncontrolled and causes network congestion.
The value is a percentage of the nominal time it takes to process a block of samples corresponding to one UDP block (512 bytes). This is calculated as follows:
- There are 127 blocks of I/Q data per frame (1 meta block for 128 blocks) and each I/Q data block of 512 bytes (128 samples) has a 8 bytes header (2 samples) thus there are 126 samples remaining effectively. This gives the constant 127*126 = 16002 samples per frame in the formula
This is the channel index of the Remote source in the remote instance to which the stream is connected to. Use this value to properly address the API to get status.
<h4>6.1: Desired number of FEC blocks per frame</h4>
This sets the number of FEC blocks per frame. A frame consists of 128 data blocks (1 meta data block followed by 127 I/Q data blocks) and a variable number of FEC blocks used to protect the UDP transmission with a Cauchy MDS block erasure correction. The two numbers next are the total number of blocks and the number of FEC blocks separated by a slash (/).
This is the remote stream rate calculated from the samples counter between two consecutive API polls. It is normal for it to oscillate moderately around the nominal stream rate (2).
This counter counts the unrecoverable error conditions found (i.e. 6.4 between 128 and 128 plus the number of FEC blocks) since the last counters reset.
This is the detail of the ratio shown in the gauge. Each frame block is a block of 127 ✕ 126 samples (16 bit I or Q samples) or 127 ✕ 63 samples (24 bit I or Q samples).
When the return key is hit within the address (9.2) or port (9.3) the changes are effective immediately. You can also use this button to set again these values. Clicking on this button will send a request to the API to get the distant SDRangel instance information that is displayed in the API message box (8)
When the return key is hit within the address (10.2) or port (10.3) the changes are effective immediately. You can also use this button to set again these values.
