On Tue, 20 Feb 2024, Allan Cady via ffmpeg-devel wrote:
When the silencedetect audio filter is run against long files, the
output timestamps gradually lose precision as the scan proceeds further
into the file. This is because the output format specifier ("%.6g" in
libavutil/timestamp.h) limits the total field width to six significant
digits. As the offset into the file increases, digits drop off the end,
until eventually, for offsets greater than 100000 seconds (about 28
hours), fractions of a second disappear altogether, and the timestamps
are logged as whole seconds.
This patch changes the format to "%.6f" for silencedetect, which will
give microsecond precision for all timestamps regardless of offset.
libavutil/timestamp.h exposes a macro, av_ts2timestr, as the public
interface. This macro was used by silencedetect.c, as well as other
source files. In order to fix the issue for silencedetect without
affecting other files and tests, I have added a new macro,
av_ts2timestr_fixed_precision, which uses the new format specifier.
The original av_ts_make_time_string remains, with the original
behavior.
I'd rather just to fix av_ts_make_string to not limit the number of
significant digits. Something like:
1) Print the number in decimal notation with at most 6 fractional digits.
2) Use less fractional digits if the first format would not fit into
AV_TS_MAX_STRING_SIZE.
3) Use scientific notation if the second format would not fit into
AV_TS_MAX_STRINT_SIZE.
Regards,
Marton
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