Support and General Use > Recording

(Is MP3 always using AGC?) FIXED!!

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C1u31355:
First, great respect and thanks  to rockbox. I would never have gotten my H120 if Rockbox hadn't made the thing useful.

I've been using .wav to record, but thought I would try the new mp3.

I downloaded the 0902 build and tried recording with mp3 at 320 kbps. With Line-in as the source, I plugged a dinky microphone into a battery module and spoke a little bit.

On playback, it was quiet of course, but although I had AGC off, the speech was accompanied by hiss--as if it was boosting the speech--with silence in between words. Words were also cut off entirely at a certain threshold, like a noise gate. So it was either voice-with-hiss, with words clipped off, or silence.

.wav recording had neither the hiss nor the sudden contrasts, and I hadn't changed the AGC setting.

Is it possible the mp3 recording is automatically adding AGC? Or is this a compression artifact, even at such a high bitrate?

Mmmm:
Well, it's not AGC...all that does is change the gain (which you can see by looking at the gain indicators) and if it was off it wouldn't be on anyway :). It must be compression artifacts... I haven't tried Mp3 yet so I don't know how good it is...

Toni:
Can you please make a short wav recording and compress this wav into mp3 using the mp3 encoder plugin? If the mp3 file shows the same artifacts as in the direct mp3 recording then I can investigate the reason if you make the wav available. I have only a 56k modem, so a real small wav file would be nice.

C1u31355:
Sorry about the delay on this. First I'm going to download a newer build and do some testing, and if the problem is still there, I'll upload some little files Thanks.

Toni:
I think I now know the reason for the bad quality here. The improvements on the mp3 encoder went into the encoder plugin but not into the mp3 codec. I will write a patch soon, to make these improvements available also to the mp3 encoder codec.

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