Re: arecord command line options

On Mon, 28 Sep 2020, Alan Corey wrote:

> I would say you're in danger of overthinking it, try the defaults first.

And read the man pages.

>
> Except when you say 24/192 I'm thinking 192 kbits/sec?  My usb sound

I presume he means 24 bits per sample, 192K samples per second per channel
which gives 1.2MB/s data flow (2channelsx3bytes/sample/channel x192000 samples/channel/sec)

> cards can only do 48 max.  Yours may do better.  I was just looking
> into it for SDR purposes, the tuning range depends on the max sample
> rate.  SPDIF has always seemed like the way to go, or maybe firewire.
> But you need to study the E-MU 0202 specs to be sure it can do 192.

It claims it can.

>
> On 9/28/20, Zsolt Ero <[email protected]> wrote:
>> Hello,
>>
>> I have a few questions related to arecord, which I couldn't find in
>> the man pages nor anywhere on the internet.
>>
>> My use case is very simple, I'd like to record stereo 24/192 audio
>> into a WAV file from an E-MU 0202 USB interface using an old laptop
>> (Core 2 Duo).
>>
>> For this I thought of using the device which starts with "hw:", as it
>> seems to me that it provides the least processings over it. The
>> recording works without problems, however I'm confused about the
>> options.
>>
>> What is not clear to me:
>> --mmap - should I use it or not? I'd be writing from USB to hard drive
>> a wav file.
>> --period-time, buffer-time, period-size, buffer-size - I'm totally
>> confused about these. I'd like the highest possible recording quality,
>> latency doesn't matter to me.
>> --avail-min - what is a wakeup?
>> --disable-resample/channels/format/softvol - do I need this if I
>> selected the hw: device? I'd like to record without any kind of
>> processing.

You do not want to resample. Stereo is 2 channels ( the default), you have to
figure out what format the 3 bytes of data are delivered in.

But I agree, why not try the defaults.

Note that 24/192K is way overkill. 24bits is about a 10^9=180dB dynamic range.
This is way way way more than any microphone/amplifier can deliver. They are
more like 100dB at most, from a noise floor of around 30dB to a loudest sound
(with clipping) of about 120dB. Also most of that frequency range of 
27 octaves that 192K gives you is wasted since the ear can only at best (for a
10 year old) hear about 20 octaves.


>> --test-position/coef/nowait - do I need this for my use case?
>>
>> Thanks and regards,
>> Zsolt
>>
>>
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>
>
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