[FFmpeg-devel] [PATCH v2] lavfi/drawtext: Add localtime_ms for millisecond precision

[Andreas Rheinhardt]

Thilo Borgmann:
> 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 at 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
> 
> 
> +    // manually parse format for %N (fractional seconds)
> +    begin = fmt;
> +    while ((begin = av_stristr(begin, "%"))) {
> +        tmp = begin + 1;

begin = strchr(begin, '%')

- Andreas