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Old 13.09.2017, 21:52
plip plip is offline
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Default twitch - audio on all 720p 30fps downloads messed up

Under a specific circumstance I've noticed that it seems audio on the download is wrong 100% of the time. There will be constant choppiness to the audio through the entire video (goes silent/cuts out for a split second) every few seconds, and the pitch will be all wrong almost like the audio was sped up. This can make some streamers sound like they are teenagers or even pre teen because the pitch changes so much.

Pattern for it happening:
It seems to only show up on vods starting around 7-30 or 7-31. Before that date I have never seen this happen.
When there's two 720p options (a 60 fps and a 30 fps) and you choose one with the smaller download preview size (30fps). Then the audio will be screwed up apparently 100% of the time from what I can tell.

Examples:
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**

It's not just one streamer where it happens, so here's examples from another one.
These are also the earliest dated vods I could find where it happens, in case that helps narrow down the cause:
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**
**External links are only visible to Supporters****External links are only visible to Supporters**
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Old 14.09.2017, 10:51
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Reason is simple but complex to solve
The streams contains (many) muted parts. That means the audio part no longer exists.
This leads to async/timing issues when merging the segments into a single file
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Old 14.09.2017, 10:54
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Old 14.09.2017, 11:03
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I have an Idea...
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Old 15.09.2017, 18:31
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I have a workaround. It isn't perfect but at least it will result in a playable file. Will ping here when I've finished the workaround
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Old 26.09.2017, 16:17
plip plip is offline
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I'm curious what the workaround is.

I'm also curious why 60fps doesn't have the audio problem when 30fps does.
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Old 26.09.2017, 16:25
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I had no time yet to implement the workaround.
All streams contains muted segments, but the *chunked* original one, it seems the muting happened differently than for the re-encodes
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Old 01.03.2018, 15:56
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I'm sorry but all example links are no longer available. Can you still provide examples that have this issue?
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Old 02.03.2018, 03:24
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It's too bad that Twitch deletes all videos now. Must make it much harder for you guys to figure things out if there isn't time to check on it right away because the videos end up gone.

In this case I think Twitch must have changed something at some point that made the problem go away. I'm not seeing it anymore after checking a number of 720p 30fps videos from different streamers.

If I ever do see the problem again I'll post about it, but seems to be fixed.
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Old 02.03.2018, 09:22
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Thanks for the feedback. Yes, just report back once you found a stream to reproduce the issue
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