Feature #5875


Increase maximum size of RIFO buffer to cater for higher prefill levels

Added by cquirin about 1 year ago. Updated 12 months ago.

Target version:
Start date:
Due date:
% Done:


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Some transatlantic users experience high packet loss and large jitter. High packet loss can be worked around with FEC, implemented in an external program that forwards UDP packets with redundancy. The added redundancy adds additional jitter, as packets originally lost and recovered with FEC may pass packets not lost.

The additional jitter and packet reordering is not a problem if the RIFO is run at a sufficiently high prefill level. On average the RIFO stays at that prefill level but does experience local variations that are important.

However, if the RIFO is prefilled to and kept at a high level (around 700 frames) the level gets dangerously close to the maximum RIFO length, hardcoded to 800 frames.

Increasing the RIFO size is trivial, by changing a single #define. A doubling of its size to 1600 frames (200ms) may be appropriate.

A doubling of the size may seem overkill but in absolute terms, the memory footprint of the RIFO stays low (<= 52kB).

Actions #1

Updated by laforge about 1 year ago

fine with me, feel free to send a related patch to gerrit - assuming that the default fill level stays the same, so we're just talking about the maximum usable RIFO size we're talking here.

Actions #2

Updated by cquirin about 1 year ago

Of course we would just increase the maximum buffer size. The default prefill does not get touched. This feature makes sense only in scenarios with high latency, high jitter, high packet loss and FEC.

Actions #3

Updated by laforge 12 months ago

  • Status changed from New to Resolved
  • % Done changed from 0 to 100

Merged in

commit 632517011d756da5b0e5ddb38348df0454254621
Author: Christoph Lauter <>
Date:   Thu Jan 26 09:45:45 2023 -0700

    Increasing max FIFO size for feature request 5875, adapting tests

    Change-Id: Iae76d87cf436c80c005a2f8fce5a30f74f7e4545

As the commitlog didn't states "Closes: OS#5875", this issue was not closed automatically.


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