[FFmpeg-devel] [PATCH] avformat/hlsenc: increase initial program date time precision

[Marton Balint]

On Sun, 19 Jul 2020, Steven Liu wrote:

> Zhao Zhili <quinkblack at foxmail.com> 于2020年7月19日周日 下午6:26写道：
>>
>>
>>
>> > On Jul 19, 2020, at 5:20 PM, Steven Liu <lingjiujianke at gmail.com> wrote:
>> >
>> > Marton Balint <cus at passwd.hu> 于2020年7月19日周日 上午6:04写道：
>> >>
>> >> Also query time only once, not for every variant stream, otherwise variant
>> >> streams might get a slightly different initial program date time. And we can
>> >> set this unconditionally because HLS_PROGRAM_DATE_TIME flag is checked
>> >> elsewhere.
>> >>
>> >> Signed-off-by: Marton Balint <cus at passwd.hu>
>> >> ---
>> >> libavformat/hlsenc.c | 8 ++------
>> >> 1 file changed, 2 insertions(+), 6 deletions(-)
>> >>
>> >> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
>> >> index df84e6487d..39ff1fa1e7 100644
>> >> --- a/libavformat/hlsenc.c
>> >> +++ b/libavformat/hlsenc.c
>> >> @@ -2704,6 +2704,7 @@ static int hls_init(AVFormatContext *s)
>> >>     char *p = NULL;
>> >>     int http_base_proto = ff_is_http_proto(s->url);
>> >>     int fmp4_init_filename_len = strlen(hls->fmp4_init_filename) + 1;
>> >> +    double initial_program_date_time = av_gettime() / 1000000.0;
>> > is it AV_TIME_BASE?
>>
>> According to the documentation of av_gettime, it's not related to AV_TIME_BASE.
>>
>> /**
>>  * Get the current time in microseconds.
>>  */
>> int64_t av_gettime(void);
> I saw
> /**
> * Internal time base represented as integer
> */
>
> #define AV_TIME_BASE            1000000
> Do you mean cannot av_gettime() / AV_TIME_BASE?

av_gettime() is always microsec according to docs, even if AV_TIME_BASE is 
not 1000000. In practice however AV_TIME_BASE is assumed to be 1000000 in 
a lot of places, so one can't really change it.

IMHO it is cleaner to use 1000000.0 instead of AV_TIME_BASE, because 
AV_TIME_BASE is integer, so you'd have to use (double)AV_TIME_BASE and 
that would be ugly. So I'd rather keep 1000000.0.

Regards,
Marton

>>
>> >>
>> >>     if (hls->use_localtime) {
>> >>         pattern = get_default_pattern_localtime_fmt(s);
>> >> @@ -2798,12 +2799,7 @@ static int hls_init(AVFormatContext *s)
>> >>         vs->start_pts = AV_NOPTS_VALUE;
>> >>         vs->end_pts   = AV_NOPTS_VALUE;
>> >>         vs->current_segment_final_filename_fmt[0] = '\0';
>> >> -
>> >> -        if (hls->flags & HLS_PROGRAM_DATE_TIME) {
>> >> -            time_t now0;
>> >> -            time(&now0);
>> >> -            vs->initial_prog_date_time = now0;
>> >> -        }
>> >> +        vs->initial_prog_date_time = initial_program_date_time;
>> >>
>> >>         for (j = 0; j < vs->nb_streams; j++) {
>> >>             vs->has_video += vs->streams[j]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO;
>> >> --
>> >> 2.26.2
>> >>
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