Unable to reproduce the issue on reported chrome version 63.0.3239.84 and latest canary 65.0.3306.0 using Mac 10.13.1 with steps mentioned below

Steps followed to reproduce the issue:
1) Launched chrome reported version
2) Downloaded the attachment provided in comment#0
3) Ran the file and allowed camera and mic access
4) Clicked on record then compute and then stop, then played the video, video played normally
5) Downloaded the video (downloaded video is in webem format,as firefox didn't allowed webem format to play, so converted it to MP4 and played it in firefox) and played it
6) video played normally

@Reporter:
Please find the attached videos for your reference and let us know if we have missed anything in reproducing the issue, try to test the issue by creating new person with no extensions and apps in it and le us know if the issue still persists.
1) Video.webem is the direct downloaded file and 
2) webem to mp4.mp4 is the converted file

Thanks!

Deleted: video.webm 284 KB

	video.webm 284 KB View Download

Deleted: webem to mp4.mp4 837 KB

	webem to mp4.mp4 837 KB View Download

We're experiencing the same issue. Audio will play back seemingly fine (in Chrome), but the audio moves out of sync over time (due to dropped frames). To know whether the file is actually okay, run the opusinfo utility on it.

Could it possibly help to increment the timeslice supplied in MediaRecorder#start?

Hmm we should be managing (in particular the compression of) audio and video 
on background threads, so they should not be influenced by a hogging of the
Render main thread (unless this overloads the whole CPU). 

Could you please make a simplified codepen.io or some such and add it to the
bug? 

There is already a simplified case in html page attached. Here it is on codepen https://codepen.io/anon/pen/bLByWr

The important thing I think I have to state one more time, is that I get sound gaps when I try to play or decode the resulting file in something other than Chrome.

Thank you for providing more feedback. Adding requester "sc00335628@techmahindra.com" to the cc list and removing "Needs-Feedback" label.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

#7 ah, hmm, so chrome plays back the file fine (no gaps) but other
browsers and external players play it with gaps. 

dalecurtis@, flim@, any ideas what could be going on?

Not sure why you'd get audio gaps, the audio should eventually arrive IIRC how you're doing this (post-task audio as it arrives).

If the processor is hogged enough that audio or video are underflowing though the media pipeline will drop video/audio frames before MR ever sees them.

Would that be of any help if I send an example video file with sound issues?

Thanks for the codepen example.

We took a look and saw that audio frames aren't being dropped, instead multiple frames were generated consecutively with the same timestamp. The total length of these additional frames correspond to the audio gap heard in other browsers/players.

The issue might be that when the capture/muxer becomes unblocked after "Compute", it releases a bunch of buffered audio frames with the same timestamp. It also looks like Chrome playback isn't taking the timing of these frames into consideration.

The NextAction date has arrived: 2018-02-15

The standard playback path doesn't use timestamps for audio packets, its clock is driven purely by the number of samples.

Ping for triaging.

Retried the issue on Mac OS 10.13.3 on the latest Stable 66.0.3359.181 and Canary 68.0.3438.0 and unable to reproduce the issue by following the below steps.

1. Launched Chrome and navigated to the given codepen https://codepen.io/anon/pen/bLByWr in comment #7.
2. Recorded a video, downloaded it and played it on Firefox.
3. Can observe that the file is playing without any issues and no distortions are observed.

w0rse.t@ request you to update chrome to the latest Stable 66.0.3359.181, retry the issue and update the thread with the observations, which will help in further triaging.

Thanks.. 

I'm still able to reproduce the bug with a codepen case on Mac OS 10.13.4 in latest Chrome stable 66.0.3359.181

One deviation from your steps is, I'm unable to playback the downloaded file in Firefox - it gives me "No video with supported format and MIME type found" error. Instead I use VLC to play the file. There's no sound in places where I pressed Compute button during video recording. Have you pressed Compute button during video recording?

As before, the same codepen produces video file with no sound gaps when run in Firefox.

Thank you for providing more feedback. Adding the requester to the cc list.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

Able to reproduce the issue on Mac 10.13.3 and Win-10 using chrome latest stable #66.0.3359.181 and latest canary #68.0.3438.0. 
Note: Unable to test the issue on ubuntu 17.10 as on computing the recorded video did not produce any sound.
This is a non-regression issue as it is observed from M60 old builds. 

Hence, marking it as untriaged to get more inputs from dev team.

Thanks...!!

 Issue 761840  has been merged into this issue.

 Issue 787596  has been merged into this issue.

 w0rse.t@gmail.com, let's continue the conversation in Issue 873963