26da3d0069
Previously, these tests failed when running on Windows, if the
system is configured with a time zone east of Greenwich, i.e.
with a positive GMT offset.
The muxer converts the creation_date given by the user using
av_parse_time to unix time, as a time_t. The creation_date is
interpreted as a local time, i.e. according to the current time
zone. (This time_t value is then converted back to a broken out
local time form with localtime_r.)
The given reference date/time, "1970-01-01T00:00:00", is the
origin point for unix time, corresponding to time_t zero. However
when interpreted as local time, this doesn't map to exactly zero.
Time zones east of Greenwich reached this time a number of hours
before the point of zero time_t - so the corresponding time_t
value essentially is minus the GMT offset, in seconds.
Windows mktime returns an error, returning (time_t)-1, when given
such a "struct tm", while e.g. glibc mktime happily returns a
negative time_t. av_parse_time doesn't check the return value of
mktime for potential errors.
This is observable with the following test snippet:
struct tm tm = { 0 };
tm.tm_year = 70;
tm.tm_isdst = -1;
tm.tm_mday = 1;
tm.tm_hour = 0;
time_t t = mktime(&tm);
printf("%d-%02d-%02d %02d:%02d:%02d\n", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec);
printf("t %d\n", (int)t);
By varying the value of tm_hour and the system time zone, one
can observe that Windows mktime returns -1 for all time_t values
that would have been negative.
This range limit is also documented by Microsoft in detail at
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/mktime-mktime32-mktime64.
To avoid the issue, pick a different, arbitrary reference time,
which should have a nonnegative time_t for all time zones.
(cherry picked from commit 13139d6d83e8bdcf8a2c81af14ed2c3e30b5e1c1)
Signed-off-by: Martin Storsjö <martin@martin.st>
77 lines
3 KiB
Plaintext
77 lines
3 KiB
Plaintext
File Format=MacCaption_MCC V2.0
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///////////////////////////////////////////////////////////////////////////////////
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// Computer Prompting and Captioning Company
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// Ancillary Data Packet Transfer File
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//
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// Permission to generate this format is granted provided that
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// 1. This ANC Transfer file format is used on an as-is basis and no warranty is given, and
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// 2. This entire descriptive information text is included in a generated .mcc file.
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//
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// General file format:
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// HH:MM:SS:FF(tab)[Hexadecimal ANC data in groups of 2 characters]
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// Hexadecimal data starts with the Ancillary Data Packet DID (Data ID defined in S291M)
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// and concludes with the Check Sum following the User Data Words.
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// Each time code line must contain at most one complete ancillary data packet.
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// To transfer additional ANC Data successive lines may contain identical time code.
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// Time Code Rate=[24, 25, 30, 30DF, 50, 60, 60DF]
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//
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// ANC data bytes may be represented by one ASCII character according to the following schema:
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// G FAh 00h 00h
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// H 2 x (FAh 00h 00h)
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// I 3 x (FAh 00h 00h)
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// J 4 x (FAh 00h 00h)
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// K 5 x (FAh 00h 00h)
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// L 6 x (FAh 00h 00h)
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// M 7 x (FAh 00h 00h)
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// N 8 x (FAh 00h 00h)
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// O 9 x (FAh 00h 00h)
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// P FBh 80h 80h
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// Q FCh 80h 80h
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// R FDh 80h 80h
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// S 96h 69h
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// T 61h 01h
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// U E1h 00h 00h 00h
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// Z 00h
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//
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///////////////////////////////////////////////////////////////////////////////////
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UUID=0087C4F6-A6B4-5469-8C8E-BBF44950401D
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Creation Program=FFmpeg
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Creation Date=Friday, January 2, 1970
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Creation Time=00:00:00
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Time Code Rate=30DF
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00:00:58:29 T49S494F43ZZ72F4QROO74ZZBFAB
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