Re: [FFmpeg-devel] [PATCH] Add init_program_date_time so start time can be specified

[epirat07@gmail.com]

On 18 Oct 2023, at 3:14, David Johansen wrote:

> On Tue, Oct 17, 2023 at 7:09 PM <epirat07@gmail.com> wrote:
>
>>
>>
>> On 17 Oct 2023, at 17:51, Dave Johansen wrote:
>>
>>> ---
>>>  doc/muxers.texi      | 3 +++
>>>  libavformat/hlsenc.c | 7 ++++++-
>>>  2 files changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/doc/muxers.texi b/doc/muxers.texi
>>> index f6071484ff..87c19a5cb9 100644
>>> --- a/doc/muxers.texi
>>> +++ b/doc/muxers.texi
>>> @@ -1086,6 +1086,9 @@ seeking. This flag should be used with the
>> @code{hls_time} option.
>>>  @item program_date_time
>>>  Generate @code{EXT-X-PROGRAM-DATE-TIME} tags.
>>>
>>> +@item init_program_date_time
>>> +Time to start program date time at.
>>> +
>>>  @item second_level_segment_index
>>>  Makes it possible to use segment indexes as %%d in hls_segment_filename
>> expression
>>>  besides date/time values when strftime is on.
>>> diff --git a/libavformat/hlsenc.c b/libavformat/hlsenc.c
>>> index 4ef84c05c1..474322cc21 100644
>>> --- a/libavformat/hlsenc.c
>>> +++ b/libavformat/hlsenc.c
>>> @@ -28,6 +28,8 @@
>>>  #include <unistd.h>
>>>  #endif
>>>
>>> +#include "float.h"
>>> +
>>>  #include "libavutil/avassert.h"
>>>  #include "libavutil/mathematics.h"
>>>  #include "libavutil/avstring.h"
>>> @@ -212,6 +214,8 @@ typedef struct HLSContext {
>>>      int64_t recording_time;
>>>      int64_t max_seg_size; // every segment file max size
>>>
>>> +    double init_program_date_time;
>>> +
>>>      char *baseurl;
>>>      char *vtt_format_options_str;
>>>      char *subtitle_filename;
>>> @@ -2867,7 +2871,7 @@ 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;
>>> +    double initial_program_date_time = hls->init_program_date_time ?
>> hls->init_program_date_time : av_gettime() / 1000000.0;
>>>
>>>      if (hls->use_localtime) {
>>>          pattern = get_default_pattern_localtime_fmt(s);
>>> @@ -3141,6 +3145,7 @@ static const AVOption options[] = {
>>>      {"split_by_time", "split the hls segment by time which user set by
>> hls_time", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_SPLIT_BY_TIME }, 0, UINT_MAX,
>>  E, "flags"},
>>>      {"append_list", "append the new segments into old hls segment
>> list", 0, AV_OPT_TYPE_CONST, {.i64 = HLS_APPEND_LIST }, 0, UINT_MAX,   E,
>> "flags"},
>>>      {"program_date_time", "add EXT-X-PROGRAM-DATE-TIME", 0,
>> AV_OPT_TYPE_CONST, {.i64 = HLS_PROGRAM_DATE_TIME }, 0, UINT_MAX,   E,
>> "flags"},
>>> +    {"init_program_date_time", "Time to start program date time at",
>> OFFSET(init_program_date_time), AV_OPT_TYPE_DOUBLE, {.dbl = 0 }, 0,
>> DBL_MAX,   E},
>>
>> This should probably not be mixed into the flags options list.
>>
>> It seems odd to have the user provide a double here instead of a ISO 8601
>> datetime, which is what the spec requires / ends up in the playlist.
>> If you do not want to handle the datetime string parsing, at least it
>> would be good to give a hint what exactly the double value is expected to
>> be here.
>>
>> However usability-wise I would prefer to accept a proper date/time here…
>>
>
> Is there an example of how to accept a string as the option and then do the
> parsing that I could base the code on?

For the option itself, just change the type (of course adjust the struct variable as well):

{"init_program_date_time", "Time to start program date time at",
 OFFSET(init_program_date_time), AV_OPT_TYPE_STRING, .flags = E},

And for parsing maybe have a look at libavformat/dashdec.c around line 191 which does
rudimentary ISO-8601 parsing.

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