Re: [FFmpeg-devel] [PATCH v5 2/3] fftools/opt_common: add time and datetime log flags

[Tobias Rapp <t.rapp@noa-archive.com>]

On 07/02/2025 12:27, Soft Works wrote:

>
>> -----Original Message-----
>> From: ffmpeg-devel<ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of
>> Tobias Rapp
>> Sent: Friday, February 7, 2025 11:42 AM
>> To:ffmpeg-devel@ffmpeg.org
>> Subject: Re: [FFmpeg-devel] [PATCH v5 2/3] fftools/opt_common: add
>> time and datetime log flags
>>
>> On 07/02/2025 08:57, softworkz wrote:
>>
>>> From: softworkz<softworkz@hotmail.com>
>>>
>>> This commit adds two logging flags: 'time' and 'datetime'.
>>>
>>> Usage:
>>>
>>> ffmpeg -loglevel +time
>>>
>>> or
>>>
>>> ffmpeg -loglevel +datetime
>>>
>>> Setting av_log_set_flags(0) in term_exit in ffmpeg.c prevents
>>> timing to be printed when exiting.
>>>
>>> Signed-off-by: softworkz<softworkz@hotmail.com>
>>> ---
>>>    fftools/ffmpeg.c     |  1 +
>>>    fftools/opt_common.c | 12 ++++++++++++
>>>    2 files changed, 13 insertions(+)
>>>
>>> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
>>> index dc321fb4a2..f4c717afaa 100644
>>> --- a/fftools/ffmpeg.c
>>> +++ b/fftools/ffmpeg.c
>>> @@ -130,6 +130,7 @@ static void term_exit_sigsafe(void)
>>>
>>>    void term_exit(void)
>>>    {
>>> +    av_log_set_flags(0);
>>>        av_log(NULL, AV_LOG_QUIET, "%s", "");
>>>        term_exit_sigsafe();
>>>    }
>> If I understand the purpose of AV_LOG_QUIET correctly the correct way
>> would be to skip writing time/datetime information in the log writer
>> itself (part of patch #1 in this patch-set) if level is <=
>> AV_LOG_QUIET,
>> rather than clearing the flags here.
>>
>> Regards,
>> Tobias
>
> Hi Tobias,
>
> my understanding of AV_LOG_QUIET would be that when program code logs a message with that level, it will be printed even when the user has "-loglevel quiet".
> I would wonder why such log messages shouldn't be prefixed with the time (normally).
> To me it appears that the special case is rather the log invocation on exit which prints - well: nothing.
>
> I'd rather question why it is not printing the log level for quiet. Is it really intended or was it only done to make it possible to print this empty message on exit?
>
> Do I see it wrong? Then I'll change it of course.
>
> Thanks a lot for reviewing!
>
> sw

The documentation for AV_LOG_QUIET in log.h says "Print no output" and 
from grepping through code it seems the implementation matches that 
definition. The purpose of av_log(NULL, AV_LOG_QUIET, "%s", "") is 
described with the AV_LOG_SKIP_REPEATED flag, see 
https://ffmpeg.org/doxygen/trunk/group__lavu__log.html#ga6cdf5cd331b17e80e8308124f05a6db8 
.

So I suggest to just add a "(level > AV_LOG_QUIET)" clause to the added 
lines in forma_line(), similar to how it is done with the loglevel 
prefix in that function some lines below:

if (*print_prefix && (level > AV_LOG_QUIET) && (flags & (AV_LOG_PRINT_TIME | AV_LOG_PRINT_DATETIME)))
     format_date_now(&part[4], flags & AV_LOG_PRINT_DATETIME);

Regards, Tobias
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