Audacity 2.2.2 not detecting dropouts

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arlie
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Audacity 2.2.2 not detecting dropouts

Post by arlie » Sun May 06, 2018 2:04 am

I just installed 2.2.2 a week ago and generally it is working well. Three plus hours of recording. And dropouts are actually less frequent than has been my norm -- just two occurrences so far. But they have not been detected as promised in this release. I have seen the behavior described in your release notes while I was doing some output sound troubleshooting, so I know it's in there. My Audicity preferences/recording setting for "detect dropouts" is checked -- and I have double checked my version number. What could I be missing?

arlie
Posts: 17
Joined: Fri May 27, 2016 2:46 am
Operating System: OS X 10.11 El Capitan or later (macOS)

Re: Audacity 2.2.2 not detecting dropouts

Post by arlie » Sun May 06, 2018 2:28 am

Should have specified: macOS 10.13.4

Also, I have reproduced this by simply interrupting the source briefly during a recording. When I stopped the recording there was no popup message and no dropout labels.

steve
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Re: Audacity 2.2.2 not detecting dropouts

Post by steve » Sun May 06, 2018 1:01 pm

Thanks for your feedback.

I'm on Linux, and I can observer similar behaviour to what you report on your Mac.

Dropouts may occur for many reasons. Basically they occur when some part of the system cannot keep up with the amount of audio data, so some of the audio data received fails to be written to disk. I think what Audacity is doing is looking for one specific cause of dropouts - when audio data is sent by Audacity for writing to disk, but does not actually get written to disk. Other causes of dropouts are not detected.

If Audacity does not detect dropouts, that does not mean that there were no dropouts, it just means that there were no dropouts of the kind that Audacity can detect.
I have raised this issue with the Audacity team.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

arlie
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Joined: Fri May 27, 2016 2:46 am
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Re: Audacity 2.2.2 not detecting dropouts

Post by arlie » Sat Jun 23, 2018 8:23 pm

Resuming a discussion from a month ago, MacOS 10.13.5 and Audacity 2.2.2:

If Audacity detects (looks for) dropouts when it sends data that does not get written, will that include dropouts which are due to the buffer size setting? Dropouts have been my major inconvenience since I started recording from streaming audio 2 years ago. Last January I spent quite a bit of time experimenting with opening and closing windows, minimizing windows, zooming out on the Audacity display, and tinkering with the latency settings. Then I would watch the activity monitor for cpu usage. One result was that I actually increased the buffer length to 150 milliseconds. When my dropout frequency became less onerous I proceeded with all settings as-is. Since my dropouts aren't detected now can I rule out latency settings as a source?

Second question: I say "actually increased" the buffer length because I believe your documentation suggests reducing buffer length for recent versions of MacOS. Why is that?

steve
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Re: Audacity 2.2.2 not detecting dropouts

Post by steve » Mon Jun 25, 2018 11:05 am

arlie wrote:I believe your documentation suggests reducing buffer length for recent versions of MacOS. Why is that?
Generally, using a larger buffer allows the computer more time to write data to disk, so it "should" reduce the likelihood of drop outs. However, it has been observed that Apple changed something on Mac computers such that drop outs would occur if the buffer is set too long. It is unclear why this happens, but it often does, hence the updated information about trying a smaller buffer size.
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

arlie
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Re: Audacity 2.2.2 not detecting dropouts

Post by arlie » Mon Jun 25, 2018 2:33 pm

Thanks. But when a dropout occurs due to buffer latency, should that, theoretically, be flagged in 2.2.2?

Also -- and quite coincidentally -- I did start getting these dropout notifications the other night. On one occasion the recording stopped completely. (I had never seen that before.) The popup notification suggested a resource problem. It asked, e.g., if I might be writing to an external drive! Well, I had in the few days prior loaded a lot of data on the hard drive, but Audacity said I still had 570 or so hours worth of space available. What I didn't do was shutdown and restart to clear up possible allocated resources, which I think I have seen recommended in one of your tutorials or FAQs. The question buried in this is simply whether this type of thing occurs very often -- i.e. write failures with plenty of space left. (And Macs supposedly don't have to defrag.)

I have since removed thirty gigs of audio files.

One final question/observation: I have been alternating between two browsers recently, having read that Firefox ran much faster and more efficiently than Safari. Of course only one was open at the time but the other may have been holding resources. Is one browser better than another when recording web streaming in Audacity?

steve
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Re: Audacity 2.2.2 not detecting dropouts

Post by steve » Mon Jun 25, 2018 2:49 pm

arlie wrote:Thanks. But when a dropout occurs due to buffer latency, should that, theoretically, be flagged in 2.2.2?
Drop out detection is a new feature in 2.2.2 and has been revised in the upcoming 2.3.0 version. The documentation for this feature is still quite sparse, but as I understand it, in Audacity 2.2.2, drop outs that occur "downstream" from Audacity are detected, but "upstream" dropouts are not. I think the intention for Audacity 2.3.0 is that upstream drop outs will also be detected, though until the "code freeze" prior to release, everything is subject to change.
arlie wrote:One final question/observation: I have been alternating between two browsers recently, having read that Firefox ran much faster and more efficiently than Safari. Of course only one was open at the time but the other may have been holding resources. Is one browser better than another when recording web streaming in Audacity?
Either browser should work. The usual cause of drop outs when recording internet streams is due to network congestion rather than actual audio issues. Downloading from the Internet is much more reliable, often better quality and usually much quicker than recording.

If audio is only available for live streaming and not for download, then that is usually an indication that the license terms prohibit downloading.
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arlie
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Joined: Fri May 27, 2016 2:46 am
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Re: Audacity 2.2.2 not detecting dropouts

Post by arlie » Mon Jun 25, 2018 3:50 pm

Thanks again. My recordings are just the new-fashioned way of doing old-fashioned air checks. I must say that I am surprised -- and very satisfied -- with the quality of the results. That applies to the streaming source -- an FM radio station -- and the Audacity recording process. Digital audio files should be robust -- and they ARE! Who knew?

To be clear, I am talking about on demand streaming, not live streaming. Two different subjects, with two different transfer protocols, as I understand it. And these recordings never leave the house. I might add that on one occasion I did record from Spotify premium. Then I compared the result with the source CD (via a literal A/B switch) and heard no difference. I have three or four releases of the source CD, so no musician's royalties should be considered infringed. And the experiment has been deleted.

Consider this a satisfied user's testimonial to Audacity.

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