ok, thanks a lot for your answer even i can’t understand 
I don’t know what to think about dashcam recommendations : " Direct Upload (Recommended)
“* Upload videos located in path/to/videos directly to Mapillary. Videos are moved to path/to/videos/uploaded folder after upload. Videos that do not contain valid imagery are not uploaded to minimize bandwidth usage. Sampling is performed in the cloud so no extra disk space is required. This command supports the front camera video from the Blackvue DR900s (1-channel and 2-channel) models.”
So if i make this, i obtain lag due to process on mapillary serveur 