Unexpected VTT drift -> subtitle overlayed and audio/video mismatch may even reach a few seconds

Dear all

The VTT has been checked on-prem with the original source and is sync, but when overlay-ed by bitmovin rendering the trans-coded proxy, there’s a drift. Have you heard of a similar issue before?

Thanks in advance.


PS: note → at the beginning of the file, the VTT texts and audio/video frames seem to be aligned. But, progressively, they are less and less synch’ed, due to that discrete-but-increasing drift (that may even reach about 6 seconds at the end)

Hi Hugo,
Thanks for reaching out to us.
Please could you specify :

  • impacted platforms
  • player version / does it work with the latest player version
  • does reloading the stream solves the issue ?
  • if the issue happens after eg. 120s of playback, does seeking right away to 120s and hit play reproduces the issue ?
  • Test stream

Thanks in advance for your feedback. We’ll investigate accordingly

Hi Ludovic

sincere apologies, it was our fault.
Something wrong on our side.
Thank you anyway
Kind Regards


Thanks for your feedback. I’ll close the case then. Please feel free to reach out to us again if needed

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