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DIFFERENCE IN FRAME #6490
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HLS.js appends audio and video in MSE SourceBuffers based on the sample timestamps found in the media. Appended media is decoded and rendered by the browser according to its mapping of decode and presentation timestamps (DTS/PTS) to HTMLMediaElement currentTime. Some common causes for video frames not aligning with the original source are:
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Probing your first segment shows that audio starts 0.12s before video:
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Thanks a bunch Rob for your prompt response.
The probe is correct, the video does start at frame 3. However for some
reason HLS.js is adding 2-3 frames at the beginning, which means I can see
the video only at frame 6.
Although, when I use videojs' native HLS, the video starts exactly at frame
3. I like HLS.js as it gives me a lot of flexibility, however frame
accuracy is sacrosanct for the app that I am building. Not sure if you can
do something about this. I would be very happy if something can be done.
Regards,
RAVI NAIR
…On Thu, 13 Jun 2024 at 21:42, Rob Walch ***@***.***> wrote:
HLS.js appends audio and video in MSE SourceBuffers based on the sample
timestamps found in the media. These then decoded and rendered by the
browser according to its mapping of decode and presentation timestamps
(DTS/PTS) to HTMLMediaElement currentTime. Some common causes for video
frames not aligning with the original source are:
1. Audio priming delay: AAC encoding adds samples to the start that
cannot be clipped in TS or MSE which offsets video
2. Composition time (lets call this CTS - it is the difference between
PTS and DTS) applied to DTS/PTS on HTMLMediaElement time (CTS is added to
the position of appended segments)
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What version of Hls.js are you using?
1.4.0
What browser (including version) are you using?
Chrome
What OS (including version) are you using?
Linux
Test stream
https://streams.abs.tv:8443/videos/82/Videos/RTV_PRG_Whickers_World_S03E06.mp4/chunk.m3u8
Configuration
Additional player setup steps
No response
Checklist
Steps to reproduce
Expected behaviour
should not add additional frames in the beginning or the end
What actually happened?
An additional 2-3 frames get automatically added at the beginning of video which necessarily means that the video Timecodes with seek is off by 2-3 frames
Console output
Chrome media internals output
No response
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