Quoted from here:

green gfx bugs while playing avi file encoded with ultimotion codec

most likely libavfilter-caused regression

Can someone here explain in more detail?

  • Have you already looked up "regression" on the dictionary?
    – Thursagen
    Sep 8, 2011 at 9:08
  • @Thursagen,yes, but non match in this case. Sep 8, 2011 at 9:12

3 Answers 3


The word "regression" has a specific meaning in programming, which can be found in Wiktionary:

(programming) The reappearance of a bug in a piece of software that had previously been fixed.

Thus, "regression" in the text provided seems to imply that there had been bugs previous to this.

  • +1 This definition makes clear that regression occurs only when the bug in question previously existed and was fixed. This implies that anything else is not regression, even if the current state is somehow worse than a previous state.
    – Ed Guiness
    Sep 8, 2011 at 10:04

In this case, regression is referring to a software bug that was fixed earlier, but has reappeared due to changes to the software or the modules it depends on.

In software development, it is common to do regression testing. This is a process which is done either manually, by a quality assurance (QA) team, or automatically using a set of unit tests. It is done to ensure that operations that were working before changes were made to the software still work after the changes were made. If the changes cause things to break, those breakages are known as regressions.

  • 1
    Not necessarily "a set of unit tests", I would rather say that when a "unit" is changed we run a regression test in order to clarify that the unit do not disturb other units of the system. Sep 13, 2016 at 8:32

It is a type of bug where something known to have worked in the past has stopped working. This jargon use of the word "regression" is based on the physiological sense of reverting to a less-developed state.

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