Am 20.01.22 um 13:04 schrieb Thilo Borgmann:
> Am 19.01.22 um 04:16 schrieb "zhilizhao(赵志立)":
>>
>>
>>> On Jan 18, 2022, at 8:52 PM, Thilo Borgmann <thilo.borgmann@mail.de> wrote:
>>>
>>> Am 16.01.22 um 12:06 schrieb Nicolas George:
>>>> Thilo Borgman (12022-01-14):
>>>>> v6 does:
>>>>>
>>>>> $> ffmpeg ... drawtext="fontfile=...:text='%{localtime   \:%a %b %d %Y %S}'"           (seconds)
>>>>> $> ffmpeg ... drawtext="fontfile=...:text='%{localtime_ms\:%a %b %d %Y %S}'"           (milliseconds)
>>>>>
>>>>> I suggest v7 should according to your remark:
>>>>>
>>>>> $> ffmpeg ... drawtext="fontfile=...:text='%{localtime   \:%a %b %d %Y %S}'"           (seconds)
>>>>> $> ffmpeg ... drawtext="fontfile=...:text='%{localtime   \:%a %b %d %Y %S}':show_ms=1" (milliseconds)
>>>>>
>>>>> Good?
>>>>
>>>> I dislike both versions, from a user interface point of view: if there
>>>> is a format string, then it stands to reason, for the user, that the
>>>> resulting text is governed by the format string, not by an extra option
>>>> somewhere else.
>>>>
>>>> There is no "use_four_digit_year=1" option, there is %Y instead of %y.
>>>>
>>>> There is no "use_slashes=1" option, you write %Y/%m/%d instead of
>>>> %Y-%m-%d.
>>>>
>>>> There are no "omit_date=1" and "omit_hour=1" options, you just write
>>>> what you want in the format string.
>>>>
>>>> My proposal goes the same way:
>>>>
>>>> $> ffmpeg ... drawtext="fontfile=...:text='%{localtime   \:%a %b %d %Y %S.%3N}'"
>>>>
>>>> It has several merits over your proposal:
>>>>
>>>> - It can be extended later to support printing the milliseconds at
>>>>   another place than the end (for example to put the time in brackets).
>>>>
>>>> - It can be extended to support microseconds or centiseconds (%6N, %2N).
>>>>
>>>> - It is somewhat compatible with GNU date and possibly a few others.
>>>>
>>>> And I do not think it is harder to implement.
>>>
>>> Ok, did introduce a variable: %[1-6]N
>>> Parsing and clipping value to valid range of 1-6.
>>> Default 3.
>>>
>>> That way it is position independent and can show any number of decimals from 1 to 6.
>>>
>>
>>> diff --git a/libavfilter/vf_drawtext.c b/libavfilter/vf_drawtext.c
>>> index 2a88692cbd..448b174dbb 100644
>>> --- a/libavfilter/vf_drawtext.c
>>> +++ b/libavfilter/vf_drawtext.c
>>> @@ -51,6 +51,7 @@
>>>   #include "libavutil/opt.h"
>>>   #include "libavutil/random_seed.h"
>>>   #include "libavutil/parseutils.h"
>>> +#include "libavutil/time.h"
>>>   #include "libavutil/timecode.h"
>>>   #include "libavutil/time_internal.h"
>>>   #include "libavutil/tree.h"
>>> @@ -1045,14 +1046,82 @@ static int func_strftime(AVFilterContext *ctx, AVBPrint *bp,
>>>                            char *fct, unsigned argc, char **argv, int tag)
>>>   {
>>>       const char *fmt = argc ? argv[0] : "%Y-%m-%d %H:%M:%S";
>>> +    int64_t unow;
>>>       time_t now;
>>>       struct tm tm;
>>> -
>>> -    time(&now);
>>> -    if (tag == 'L')
>>> +    char *begin;
>>> +    char *tmp;
>>> +    int len;
>>> +    char *fmt_new;
>>> +    const char *fmt_tmp;
>>> +    int div;
>>> +
>>> +    unow = av_gettime();
>>> +    now  = unow / 1000000;
>>> +    if (tag == 'L' || tag == 'm')
>>>           localtime_r(&now, &tm);
>>>       else
>>>           tm = *gmtime_r(&now, &tm);
>>> +
>>> +    // manually parse format for %N (fractional seconds)
>>> +    begin = (char*)fmt;
>>
>> Make begin and tmp const char *, so the cast can be removed.
>>
>>> +    while ((begin = av_stristr(begin, "%"))) {
>>
>> How about strstr() since ‘%’ is caseless?
>>
>>> +        tmp = begin + 1;
>>> +        len = 0;
>>> +        // count digits between % and possible N
>>> +        while (*tmp != '\0' && av_isdigit((int)*tmp)) {
>>> +            len++;
>>> +            tmp++;
>>> +        }
>>> +        // N encountered, insert time
>>> +        if (*tmp == 'N') {
>>> +            int num_digits = 3; // default show millisecond [1,6]
>>> +
>>> +            // if digits given, parse as number in [1,6]
>>> +            if (len > 0) {
>>> +                av_sscanf(begin + 1, "%i", &num_digits);
>>> +                num_digits = av_clip(num_digits, 1, 6); // ensure valid value
>>
>> We can ignore len > 1, then the code can be simplified as
>>
>> if (len == 1)
>>      num_digits = av_clip(*(begin + 1) - ‘\0’, 1, 6)
>>
>>
>>> +            }
>>> +
>>> +            len += 2; // add % and N to get length of string part
>>> +
>>> +            switch(num_digits) {
>>> +            case 1:
>>> +                fmt_tmp = "%.*s%01d%s";
>>> +                div     = 100000;
>>> +                break;
>>> +            case 2:
>>> +                fmt_tmp = "%.*s%02d%s";
>>> +                div     = 10000;
>>> +                break;
>>> +            case 3:
>>> +                fmt_tmp = "%.*s%03d%s";
>>> +                div     = 1000;
>>> +                break;
>>> +            case 4:
>>> +                fmt_tmp = "%.*s%04d%s";
>>> +                div     = 100;
>>> +                break;
>>> +            case 5:
>>> +                fmt_tmp = "%.*s%05d%s";
>>> +                div     = 10;
>>> +                break;
>>> +            case 6:
>>> +                fmt_tmp = "%.*s%06d%s";
>>> +                div     = 1;
>>> +                break;
>>> +            }
>>
>> The switch-case can be replaced by “%0*d” and pow(10, 6 - num_digits).
> 
> Indeed, simplified.
> 
> 
>>> +
>>> +            fmt_new = av_asprintf(fmt_tmp, begin - fmt, fmt, (int)(unow % 1000000) / div, begin + len);
>>> +            if (!fmt_new)
>>> +                return AVERROR(ENOMEM);
>>> +            av_bprint_strftime(bp, fmt_new, &tm);
>>> +            av_freep(&fmt_new);
>>> +            return 0;
>>> +        }
>>> +        begin++;
>>
>> Progress faster by taking account of len.
> 
> As well, also added to skip "%%".
> 
> 
>>> +    }
>>> +
>>>       av_bprint_strftime(bp, fmt, &tm);
>>>       return 0;
>>>   }
>>> -- 
> 
> v8 attached.

Fixed off-by-one bug.
Allows for several occurrences of %N parameter now.

v9 attached.

Thanks,
Thilo