Topic: ZOOM M2 M3 M4 MicTrak Recorders - 32 bit float dual ADC one-piece devices

[rastasean]

Some considerations for the m2/m3 mic recorders...

Neither one has a mic input of any kind. It would have been nice to have 1/8" input on both of the recorders, but Zoom didn't want to include that.
The m2 does not have a 1/4-20 thread to mount it on a tripod. You will need to use the supplied mic holder or something else.

I think the battery compartment on the m2/m4 is quite clever to work with the shape of both recorders.

[Niels]

A good-to-know piece of info related to Normalisation and 16/24bit conversion - applicable for the M4 but possibly also the M2:

If you connect the recorder in File Transfer mode to your computer or remove the SD card to listen to any of the tracks while they are still on the SD card, you will NOT be able to put the card back in the M4 and normalise or export those specific tracks to 16/24bit in the device.

The M4 will think the file is modified outside the device and refuse to proceed.

The manual does state that you can only use the Normalise and Export functions on un-edited files produced by the M4.
When you listen to the track via the PC, the computer will write to the file - probably just "last opened date/time", but that is apparently enough to be considered "edited".

In other words: If you plan to normalise/convert to 16/24bit in the device, don't listen to the file on the card with another device before doing so.

[Ozpeter]

Thank for taking the trouble to pass that on - I didn't know about it.

[TheJez]

A good-to-know piece of info related to Normalisation and 16/24bit conversion - applicable for the M4 but possibly also the M2:

If you connect the recorder in File Transfer mode to your computer or remove the SD card to listen to any of the tracks while they are still on the SD card, you will NOT be able to put the card back in the M4 and normalise or export those specific tracks to 16/24bit in the device.

The M4 will think the file is modified outside the device and refuse to proceed.

The manual does state that you can only use the Normalise and Export functions on un-edited files produced by the M4.
When you listen to the track via the PC, the computer will write to the file - probably just "last opened date/time", but that is apparently enough to be considered "edited".

In other words: If you plan to normalise/convert to 16/24bit in the device, don't listen to the file on the card with another device before doing so.

I guess taking out the SD card and setting the read-only switch on it should prevent the OS to write to it. If the OS properly obeys the switch position, that is…

Edit: stupid me! Micro SD doesn’t have such a switch! But maybe when inserting it in an adapter that does have such a switch??

[Niels]

Edit: stupid me! Micro SD doesn’t have such a switch! But maybe when inserting it in an adapter that does have such a switch??

Yes. True - there are ways to get around it if you are aware of the behaviour of the recorder.

I had made a lot (~25) of short 2-5min recordings and needed to export/normalise one specific file. Instead of navigating the slow filesystem of the recorder, I thought I could more easily identify the relevant file by connecting the M4 to my laptop via USB-C and browse the recordings that way.
I thought I would give a quick listen to make sure I had found the right one, but then ... well...

I haven't really established a workflow for converting and normalising 32bit files to 24bit. I do most of my processing in GarageBand (Mac) which seemingly treats 32bit as 24bit and therefore doesn't allow me to recover clipping parts.

I need to find a simple tool to normalise and convert a 32bit float to 24bit with as little fuss as possible on my Mac - so I can proceed in GarageBand from there.
Maybe the subject of another thread?

[rastasean]

Perhaps this?
https://github.com/slhck/ffmpeg-normalize

[TheJez]

Perhaps this?
https://github.com/slhck/ffmpeg-normalize

I gave this try, just out of curiosity. And yes, it works...

D:\hoi\test>ffmpeg-normalize clipping_32bit.wav -v -nt peak -ext wav
INFO: Normalizing file clipping_32bit.wav (1 of 1)
INFO: Running first pass astats filter for stream 0
INFO: Running second pass for clipping_32bit.wav
INFO: Adjusting stream 0 by -54.664590000000004 dB to reach -23.0
INFO: Normalized file written to normalized\clipping_32bit.wav

You could also use Audacity, which is available for Mac... It is free and does the job well.
Also, you could use just the ffmpeg command line tool in this way:

Step 1: Determine the peak amplitude

ffmpeg -i clipping_32bit_input.wav -filter_complex "ebur128=peak=true" -f null -
...
[Parsed_ebur128_0 @ 000001ce620b1280] Summary:

  Integrated loudness:
    I:          -7.1 LUFS
    Threshold: -19.1 LUFS

  Loudness range:
    LRA:        20.2 LU
    Threshold: -29.1 LUFS
    LRA low:   -22.8 LUFS
    LRA high:   -2.6 LUFS

  True peak:
    Peak:       31.7 dBFS

It tells the true peak of the input file is 31.7 (which is well above 0dB!)

Step 2: Applying gain
As the peak is 31.7, we need to apply a gain of -32 to assure all samples will be < 0dB:

ffmpeg -i clipping_32bit_input.wav -af "volume=-32dB" -c:a pcm_f32le output_normalized.wav

(The -c:a pcm_f32le option is needed to prevent the file is internally converted to 16 bit before applying the gain, as that would result in chopped-off peaks)

[Niels]

I gave this try, just out of curiosity. And yes, it works...


You could also use Audacity, which is available for Mac... It is free and does the job well.
Also, you could use just the ffmpeg command line tool in this way:

Thanks for the suggestions @rattasean and @TheJez.
I am not a complete stranger to command line apps, but it is 25 years ago I last worked with linux/unix prompts. I am not sure if my aging- and blood cloth challenged brain can reenter that state-of-mind again, so I'll probably give Audacity a try first :-)

[rastasean]

One feature i don't see available on the m4 would be to link two units together so you can have eight channels of audio.
There is a remote port, but it's smaller than 3.5mm, and even if you had a cable to connect to another m4, there's nothing in the menu to determine which is master/slave.

I remember the edirol r44 allowed you to link two recorders together, and sound devices probably have some way to do that as well.

[Niels]

One feature i don't see available on the m4 would be to link two units together so you can have eight channels of audio.
There is a remote port, but it's smaller than 3.5mm, and even if you had a cable to connect to another m4, there's nothing in the menu to determine which is master/slave.

I remember the edirol r44 allowed you to link two recorders together, and sound devices probably have some way to do that as well.

Time code is not precise enough for that?
The deck allows jam sync with other units (or being the controller).

[rastasean]

I considered that, but didn't give it much thought as I don't know much about timecode.

If both units are synced, does that mean you need to begin recording simultaneously on both units?

Time code may work well enough in the 32 fp world, since there are no levels to adjust.

[rastasean]

Has anyone had issues with the text for the buttons rubbing off on their m4?

On the front, the only labels that are present are for the transport controls. The left and right labels are also gone.

[rastasean]

I gave this try, just out of curiosity. And yes, it works...


You could also use Audacity, which is available for Mac... It is free and does the job well.
Also, you could use just the ffmpeg command line tool in this way:

Thanks for the suggestions @rattasean and @TheJez.
I am not a complete stranger to command line apps, but it is 25 years ago I last worked with linux/unix prompts. I am not sure if my aging- and blood cloth challenged brain can reenter that state-of-mind again, so I'll probably give Audacity a try first :-)

In addition to Audacity, you could take a look at Ocenaudio: https://www.ocenaudio.com/download

I first heard about it several years ago, but well after audacity. I'm not sure if it's open source, but it's a free application that you may want to try out.