[FFmpeg-devel] [PATCH] Fix loss of precision for silencedetecton large files

[Allan Cady]

  On Wednesday, March 27, 2019, 11:19:23 AM PDT, Michael Niedermayer <michael at niedermayer.cc> wrote: > this breaks make fate> > also if fate is updated it should be ensured it still checks enough precission> and that it does produce the same results (fate passes) on all relevant> platforms. This change may bring non significant differences into significance> > thanks
OK so I spent some more time familiarizing myself with the code and tests, and it's clear that making the change the way I did would probably break dozens of tests, because the function I changed, av_ts_make_time_string, is referenced (by its convenience macro av_ts2timestr) in many files (I count 21) and dozens of lines of code, in libavfilter, fftools, and libavformat.
As an alternative, I tried making a modified & renamed copy of av_ts_make_time_string/av_ts2timestr, and referencing that copy in af_silencedetect.c, leaving other references to the original function unchanged. In this case, FATE fails just a single test, filter-metadata-silencedetect. I then modified the reference output file (tests/ref/fate/filter-metadata-silencedetect) to match the changed output, and all tests then pass.
So at this point I could use some guidance from the wizards as to the best way to proceed. Not knowing any of the history or thinking that went into the design, I don't know if it makes the best sense to use the "%.6g" format for all those other timestamps, but I feel strongly that it's a poor choice for silencedetect (and probably other *detect filters), for the reason I explained originally. Is there possibly another way to get the result I want without modifying the code? Or I can imagine maybe a format specifier as a filter parameter -- is there any precedent for this?

Open to suggestions. Thanks all.
Allan