Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at https://gpac.io/downloads/gpac-nightly-builds/
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

Detailed guidelines: https://gpac.io/bug-reporting/

Hello, Thank you for your hard work. Sorry for asking a lot of questions recently.  
I want to get earliest_presentation_time value in sidx box.
I tried to use below function
```
GF_EXPORT
GF_Err gf_isom_get_sidx_duration(GF_ISOFile *movie, u64 *sidx_dur, u32 *sidx_timescale)
{
	u64 dur=0;
	u32 i;
	if (!movie || !movie->moov || !sidx_timescale || !sidx_dur)
		return GF_BAD_PARAM;

	if (!movie->main_sidx) return GF_NOT_SUPPORTED;
	*sidx_timescale = movie->main_sidx->timescale;

	for (i=0; i<movie->main_sidx->nb_refs; i++) {
		dur += movie->main_sidx->refs[i].subsegment_duration;
	}
	*sidx_dur = dur;
	return GF_OK;
}
```

My thought about this function,    
this function only return GF_NOT_SUPPORTED    
because movie->main_sidx never allocated.    

I search main_sidx ,   
I could not find using of main_sidx   
![image](https://github.com/gpac/gpac/assets/80387186/c3c1ff47-9a17-48be-85e4-8a42479a9e31)  

how to get earliest_presentation_time value in sidx box ?? 

I am file open with callback mode using "_gpac_isobmff_redirect" and    
making sidx box using ```gf`_isom_close_segment``` now.  

Inquiry about gf_isom_get_sidx_duration function 
This is a GitHub Issue
repo:gpac
owner:gpac
Title : Inquiry about gf_isom_get_sidx_duration function 
Issue date:

--- start body ---
Thanks for reporting your issue. Please make sure these boxes are checked before submitting your issue - thank you!

- [x] I looked for a similar issue and couldn't find any.
- [x] I tried with the latest version of GPAC. Installers available at https://gpac.io/downloads/gpac-nightly-builds/
- [x] I give enough information for contributors to reproduce my issue (meaningful title, github labels, platform and compiler, command-line ...). I can share files anonymously with this dropbox: https://www.mediafire.com/filedrop/filedrop_hosted.php?drop=eec9e058a9486fe4e99c33021481d9e1826ca9dbc242a6cfaab0fe95da5e5d95

Detailed guidelines: https://gpac.io/bug-reporting/

Hello, Thank you for your hard work. Sorry for asking a lot of questions recently.  
I want to get earliest_presentation_time value in sidx box.
I tried to use below function
```
GF_EXPORT
GF_Err gf_isom_get_sidx_duration(GF_ISOFile *movie, u64 *sidx_dur, u32 *sidx_timescale)
{
	u64 dur=0;
	u32 i;
	if (!movie || !movie->moov || !sidx_timescale || !sidx_dur)
		return GF_BAD_PARAM;

	if (!movie->main_sidx) return GF_NOT_SUPPORTED;
	*sidx_timescale = movie->main_sidx->timescale;

	for (i=0; i<movie->main_sidx->nb_refs; i++) {
		dur += movie->main_sidx->refs[i].subsegment_duration;
	}
	*sidx_dur = dur;
	return GF_OK;
}
```

My thought about this function,    
this function only return GF_NOT_SUPPORTED    
because movie->main_sidx never allocated.    

I search main_sidx ,   
I could not find using of main_sidx   
![image](https://github.com/gpac/gpac/assets/80387186/c3c1ff47-9a17-48be-85e4-8a42479a9e31)  

how to get earliest_presentation_time value in sidx box ?? 

I am file open with callback mode using "_gpac_isobmff_redirect" and    
making sidx box using ```gf`_isom_close_segment``` now.  

--- end body ---
