ORing AVERROR_INPUT_CHANGED and AVERROR_OUTPUT_CHANGED gives AVERROR_INPUT_CHANGED

[jrh]

The documentation for AVERROR_INPUT_CHANGED and AVERROR_OUTPUT_CHANGED states that the two can be ORed. But AVERROR_INPUT_CHANGED|AVERROR_OUTPUT_CHANGED gives a value equal to AVERROR_INPUT_CHANGED.

/libavutil/error.h:

#define AVERROR_INPUT_CHANGED      (-0x636e6701) ///< Input changed between calls. Reconfiguration is required. (can be OR-ed with AVERROR_OUTPUT_CHANGED)
#define AVERROR_OUTPUT_CHANGED     (-0x636e6702) ///< Output changed between calls. Reconfiguration is required. (can be OR-ed with AVERROR_INPUT_CHANGED)

Even though the numbers look as if ORing should work as intended, this is not the case because both are negative. The result is that "only input changed" and "both input and output changed" are indistinguishable.

[Balling]

But obviously OR means here not simple dumb OR. other such issue is in my patch here: ​https://patchwork.ffmpeg.org/project/ffmpeg/patch/20210604062818.2099-1-val.zapod.vz@gmail.com/

[Carl Eugen Hoyos]

Looks important.