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

**URL:** <https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451>\
**Category:** Support\
**Created:** [November 16, 2023, 6:59pm UTC](https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451 "2023-11-16T18:59:18Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![hugo.machefer](https://sea1.discourse-cdn.com/flex015/user_avatar/community.bitmovin.com/hugo.machefer/32/837_2.png) [@hugo.machefer](https://community.bitmovin.com/u/hugo.machefer)\
**Post date:** [November 16, 2023, 6:59pm UTC](https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451/1 "2023-11-16T18:59:18Z")

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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.

Hugo

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)

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**Author:** ![ludovic.michaud](https://sea1.discourse-cdn.com/flex015/user_avatar/community.bitmovin.com/ludovic.michaud/32/811_2.png) [@ludovic.michaud](https://community.bitmovin.com/u/ludovic.michaud)\
**Post date:** [November 20, 2023, 6:20pm UTC](https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451/2 "2023-11-20T18:20:07Z")

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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

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**Author:** ![hugo.machefer](https://sea1.discourse-cdn.com/flex015/user_avatar/community.bitmovin.com/hugo.machefer/32/837_2.png) [@hugo.machefer](https://community.bitmovin.com/u/hugo.machefer)\
**Post date:** [December 2, 2023, 6:25am UTC](https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451/3 "2023-12-02T06:25:35Z")

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Hi Ludovic

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

Hugo

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**Author:** ![ludovic.michaud](https://sea1.discourse-cdn.com/flex015/user_avatar/community.bitmovin.com/ludovic.michaud/32/811_2.png) [@ludovic.michaud](https://community.bitmovin.com/u/ludovic.michaud)\
**Post date:** [December 2, 2023, 4:59pm UTC](https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451/4 "2023-12-02T16:59:34Z")

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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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**Author:** ![system](https://us1.discourse-cdn.com/flex015/uploads/bitmovin/original/1X/1ab86334145095b0af9c5b924fa3ae6d920b6482.png) [@system](https://community.bitmovin.com/u/system)\
**Post date:** [December 2, 2023, 6:00pm UTC](https://community.bitmovin.com/t/unexpected-vtt-drift-subtitle-overlayed-and-audio-video-mismatch-may-even-reach-a-few-seconds/2451/5 "2023-12-02T18:00:08Z")

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