recording and converting to mp3

[queen]

I recorded a lesson with the command

[Dottout]

to convert to mp3 emerge media-sound/lame. the other question..sorry, dunno

[queen]

[cjubon]

I'd invoke lame with variable bitrate and medium quality, so the switch is -q 5. If you're not satisfied with the result, try -q 2. Lame has not so many filters, it may be difficult to minimize the hisses. You can try the lowpass filter (see man lame), but I think it won't make sense since your sample rate is already very low. Perhaps it would be better to edit the aiff in an audio editor first (e.g. audacity), but the best is always to take care for a good source recording. Built-in micros are mostly crapp, so I'd use an external micro.

[Akkara]

media-sound/sox can do volume adjustments, filtering, and other effects from the command line while converting file formats.

[queen]

[jcat]

CD quality is 44,100Hz, so you are way off the mark with you're original 8,000Hz, and even 11,000Hz

Recording at those low sample rates will introduce hiss, and reduce the frequency range you can record (which is half the sample rate due to the Nyquist limit).


You should try it at 44,100Hz, and you might even find 22,500 OK (given that you don't require a large frequency range to reproduce the human voice reasonably). But try 44,100Hz first and see how you get on.

You will get larger files, but when you compress to mp3 afterwards you'll find it much smaller!


Bit depth hasn't been mentioned here, but stick to 16 bit for safety's sake


And yes, you will get even better results with an external "directional" microphone as well, so you can home in on the source of the sound more and not the background noise. But try the higher sample rates first, and see if that gives you the improvement you're after.




Cheers,
jcat

[padoor]

first try recording with mic with no other signal/speech
see how much noise/hiss is recorded .this includes the motor noise of the fan/harddrive and other mechanical noise.
then cover mic face with cotton a 1/2 inch thick layer and do the same recording.
that is all the noise reduction you can get with internal mic.
with the cotton covered mic speech will come up better but will have to talk little louder.
i thought mp3 files are bigger for the same music /record length.
if you have some control on rec input level you can do better recording.
as jcat said external mic usage is best.
the alc of the recording circuitry will make certain amount of hiss which modulates the recording with hiss and noise.
you cannot expect proffessional voice recording with laptop mic anyways.
_________________
reach out a little bit more to catch it (DON'T BELIEVE the advocate part under my user name)

[queen]

[cjubon]

[queen]

[jcat]

As I said, you may find 22,500Hz is fine. Try it and see.

Anything less than that, and you will notice an increase in "hiss" or noise in the recording. This is only (but may include) background noise, but is a side effect of low sample rate PCM.



Cheers,
jcat

[cjubon]

[queen]

Yesterday I tried with 44100hz and it was ok. I recorded as flac. The total size of 3 1/2 hours was 230MB.

[queen]

[jcat]

Hz !



Cheers,
jcat

[queen]

[queen]

[jcat]

It depends on how close to the sound source you are and the sensitivity of your mic, so it's a tough one.

Basically, you want to end up with a recorded file that gets closing to the maximum allowed level, but never over that. This ensures that you get the best quality recording you can (you are using all the bits).
If you reach 0dB (on the digital scale) it will distort, this is called "clipping". Brief "clips" are ok, but if it happens frequently you'll get a distorted sound.

Normally when you record, it's a good idea to have an input level meter so that you can see how close to the maximum level you are (for your given mic gain level) in real time as you record. If one's not available then the best thing to examine the file after you've made your recording, using a package like Audacity. That way you can examine the recording for any "clipping", or whether it's too quiet (not very close to maximum level of 0dB digital), and adjust the mic level to compensate for you next recording. This will take some trial and error

You can also use a package like Audacity to edit the recording before you convert it to an mp3. that might be handy



Cheers,
jcat

[01mf02]

You may get louder recordings by enabling the "Mic boost" option in alsamixer. Hope it helps, and good luck with the recording!

[queen]