Using DR-05x, recorded file in MONO has same filesize as STEREO. Why?

[wylbur7]

I played an MP3 file on another device amd piped the output
to the DR-05x via the LINE-IN jack.

I then recorded it as an MP3 file, 32kbps, 44.1kHz, STEREO.

I then repeated the process, but recorded it as MONO instead of STEREO
(all other parameters the same).

I would think that the MONO version of the recording
would be half the size as the STEREO version,
but in fact they were essentially the same size!

I double-checked using an audio utility (SoX)
to verify that the STEREO version was indeed 2-channels,
that the MONO version was indeed 1-channel.

So, why was the MONO version the same size as the STEREO version ?

...

 

[Art Anderson]

The answer is in the manual; you have the manual I hope.

"The procedure to select the creation of a stereo or mono file is as follows.
Use the + or – button to select STEREO (default) or MONO.
If MONO is selected, a mono file is created, and the same signals are sent to both L and R level meters and output channels.
If sound is recorded in MONO in WAV format, the file size will be half that recorded in STEREO, allowing long time recording."

You wrote that you're recording in MP3. Try WAV.

 

[wylbur7]

Thanks for pointing out the blurb in the manual where it says
that recordings in MONO will be half the size as STEREO,
but only for WAV and not MP3.

I re-ran my original test, but using WAV instead of MP3,
and found that the MONO version was indeed half the size
of the STEREO version.

But the size of the WAV (16bit) MONO file was TWENTY times the size
of the MP3 (32 kbps) MONO file produced earlier.

TWENTY TIMES !!!

You see, the original purpose of my wanting to record in MP3 MONO
instead of MP3 STEREO was to save space.
I wanted to be able to record lectures and presentations
(some of which can run for several hours)
without having to constantly check whether there'll be enough space
on the SD card or having to swap SD cards.
So, it looks like recording in WAV format would not be practical
in this situation.

So, the big question is ...

Is this a baked-in characteristic of MP3
(and therefore cannot be avoided because that's how the MP3 format
is internally structured)?

In other words, do ALL digital recorders (regardless of brand or model)
produce MP3 files that are the same size
whether you specify MONO or STEREO?
Or does this happen only on the TASCAM DR-05x?

...

 

[Art Anderson]

I did some recordings on my DR-40 and it turns out the MP3 mode will record in Mono (appears as 1 track in Audactiy) and in Stereo (appears as twin tracks in Audacity) but there is no saving in the file size.
Here's the most sensible explanation I found: MP3 is all about using compression and some other trickery to save space. If the source material is essentially the same for both Left and Right, the file will only have to be a little bit larger to include the information it needs to store that small difference in content. i.e. it's not that the Mono file is ripping you off. It's the other way around. If you are actually going to record narration and presentations I think your results in either mode are the smallest files you'll get.
Someone would have to experiment with recording two isolated sources in stereo, like two people being recorded simultaneously into two microphones that are acoustically separated, or rig up two totally different music samples with one to the recorders Left and one to the Right. Hardly worth playing with in practical terms IMO.

 

[BazzBass]

But the size of the WAV (16bit) MONO file was TWENTY times the size
of the MP3 (32 kbps) MONO file produced earlier.

TWENTY TIMES !!!

you did not know that mp3 is inferior to WAV? especially 32kbps mp3? you've come to the right place then mate.

Welcome to the forum, you will learn a lot here,there are many wise men that share their years of experience. Take notes, I sure do lol

 

[Andy Kay]

simple solution - use a bigger Micro SD card they are cheap enough these days