Command used: 
`MP4Box -add BL_RPU.hevc:dv-profile=5 -add "1.eng.eac3":timescale=1000:delay=3003:sopt:gfreg=ffdmx -lang 2=eng  -brand mp42isom -ab dby1 output.mp4`

I checked the output using ffprobe to check the resulting file with this command:
`ffprobe -loglevel error -show_entries stream=start_time:stream=time_base:stream=start_pts output.mp4`

Unfortunatly in the resulting file only the timescale option is used and the delay option not used at all. 

ffprobe output I get is:

```
time_base=1/1000
start_pts=0
start_time=0.000000 
```

But I would expect:

```
time_base=1/1000
start_pts=3003
start_time=3.003000 
```

```
$ MP4Box -version

MP4Box - GPAC version 2.1-DEV-rev123-gbd1492420-master
(c) 2000-2022 Telecom Paris distributed under LGPL v2.1+ - http://gpac.io
        MINI build (encoders, decoders, audio and video output disabled)

Please cite our work in your research:
        GPAC Filters: https://doi.org/10.1145/3339825.3394929
        GPAC: https://doi.org/10.1145/1291233.1291452

GPAC Configuration: --static-bin
Features: GPAC_CONFIG_LINUX GPAC_64_BITS GPAC_HAS_SOCK_UN GPAC_MINIMAL_ODF GPAC_HAS_QJS  GPAC_DISABLE_3D
```
delay not used when using timescale
This is a GitHub Issue
repo:gpac
owner:gpac
Title : delay not used when using timescale
Issue date:

--- start body ---
Command used: 
`MP4Box -add BL_RPU.hevc:dv-profile=5 -add "1.eng.eac3":timescale=1000:delay=3003:sopt:gfreg=ffdmx -lang 2=eng  -brand mp42isom -ab dby1 output.mp4`

I checked the output using ffprobe to check the resulting file with this command:
`ffprobe -loglevel error -show_entries stream=start_time:stream=time_base:stream=start_pts output.mp4`

Unfortunatly in the resulting file only the timescale option is used and the delay option not used at all. 

ffprobe output I get is:

```
time_base=1/1000
start_pts=0
start_time=0.000000 
```

But I would expect:

```
time_base=1/1000
start_pts=3003
start_time=3.003000 
```

```
$ MP4Box -version

MP4Box - GPAC version 2.1-DEV-rev123-gbd1492420-master
(c) 2000-2022 Telecom Paris distributed under LGPL v2.1+ - http://gpac.io
        MINI build (encoders, decoders, audio and video output disabled)

Please cite our work in your research:
        GPAC Filters: https://doi.org/10.1145/3339825.3394929
        GPAC: https://doi.org/10.1145/1291233.1291452

GPAC Configuration: --static-bin
Features: GPAC_CONFIG_LINUX GPAC_64_BITS GPAC_HAS_SOCK_UN GPAC_MINIMAL_ODF GPAC_HAS_QJS  GPAC_DISABLE_3D
```
--- end body ---
