Removing crackles in recordings

[InternetStream]

Steve,

A brief and somewhat simplified explanation:

Computers are constantly switching between different tasks - reading from disk, writing to disk, check the modem, write to RAM, read from RAM, crunch some numbers, send a screen refresh to the graphics card, …
On the other hand, audio is a continuous stream of data, so there needs to be some way to avoid losing data while the computer is busy doing something else. This is accomplished with “buffers”.

When you record audio, the data does not stream directly from the sound card onto the hard drive - that would not work because as soon as the computer switches to another task you would lose some of the audio data. Instead, the audio streams into a special memory area called a “buffer”. The computer can then read from the buffer when it has time to do so, “emptying” the buffer, and the sound card can be continuously writing to the buffer “filling” the buffer.

Okay, this I knew.

Clearly there has to be some kind of synchronisation to ensure that there is always some data in the buffer when the computer wants to write data to disk, and there must be sufficient space in the buffer to provide somewhere that the sound card can dump its data. Thus the size of the buffer is important. If it is too small it could become full and the sound card may have nowhere to puts its data. This is called “buffer overflow” and causes bits of the data to be lost.

I was with you earlier, but not expecting you to say this…

When the “Buffer Length” = 100ms I get crackling.

When I change the “Buffer Length” to 20ms it seems to remove all crackling.

Based on what you said above, you would think that “more (buffer) is better” but apparently not in my case.

Large buffer size is generally not much of a problem on Windows or Linux, other than increasing the delay between receiving data and writing it to disk, but it is more of a problem for Mac computers as the macOS sound system is designed for relatively small audio buffers.

So please help me understand what is going on here…

When I interview on my iPhone and somes simultaneously on my Zoom H6, it appears both devices are recording okay.

And it appears the playback is okay if I just listen to the audio files - either from iPhone of H6 - using macOS’s Preview or some other app.

But when I open the audio files in Audacity, that is when the problems start.

So why does 20ms seem to work but 100ms does not work?

And does any of this have anything to do with my ongoing problem in this thread…

Audacity recording over itself?

Hello. Newbie to this forum. Have been using Audacity since maybe 2005. Currently, I have a MacBook Pro with macOS Sierra and Audacity 2.2.2 I use Audacity mostly to capture Internet streamingr adio shows. There was a show that I wanted to listen to this morning, but it was before I planned on getting up, so I set Audacity to start recording the Internet streaming radio station last night before I went to bed. (The idea being that it would still be recording over night and when the show st…