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EEVblog => The AmpHour Radio Show => Topic started by: mikeselectricstuff on September 28, 2010, 09:50:08 am

Title: AH#10 - audio recorder battery life
Post by: mikeselectricstuff on September 28, 2010, 09:50:08 am
Re. the issue of different battery life on WAV vs. MP3 - this is almost certainly due to the power taken for memory writes - WAV will be accessing the flash memory a lot more, and this will be where your half hour less battery life in WAV mode comes from.
Title: Re: AH#10 - audio recorder battery life
Post by: Zero999 on September 28, 2010, 03:01:03 pm
Which audio recorded are you talking about?

That makes sense but I wouldn't generalise: WAV is uncompressed so should be easier to encode which will take less processing power and could also save power for that reason. It probably varies depending on the recorder.
Title: Re: AH#10 - audio recorder battery life
Post by: mikeselectricstuff on September 28, 2010, 03:47:46 pm
Dave was queryiing why the spec for his audio recorder (can't remember model) showed slightly lower battery liife for WAV compared with MP3 and couldn't figure out why - the much higher bandwidth to external memory, and power draw of the memory during write could easily make up the discrepency, even after accounting for MP3 encoding.
Title: Re: AH#10 - audio recorder battery life
Post by: Time on September 28, 2010, 03:50:51 pm
flash access is costly in power.  Typically, a solid state drive consumes considerably more power than a normal 7200 rpm hard drive.

edit:  I retract this statement.  It was really only true for unoptimized first generation models.
Title: Re: AH#10 - audio recorder battery life
Post by: EEVblog on September 29, 2010, 12:17:26 am
Yes, it could certainly be the FLASH writes. Although I would have thought there would be some buffering with either WAV or MP3, and that these would pretty much even out in the end.

I can't help but think there could have been some power saved using WAV mode if that was (and it should have been) a design spec.

Dave.
Title: Re: AH#10 - audio recorder battery life
Post by: mikeselectricstuff on September 29, 2010, 07:57:55 am
Buffering would not make any difference - it just chages the size of the lumps of data written.
For WAV you are writing somethng like ten times as much data as MP3, so the flash device and its internal controller are active for ten times as long.
Title: Re: AH#10 - audio recorder battery life
Post by: joelby on September 29, 2010, 08:27:54 am
The MAS3587F-QI MP3 encoder chip claims a typical power consumption of 63 mA at 2.7V and <=24 kHz while encoding, which does seem fairly considerable. It sounds like an annoying task to calculate bit rates and flash write power consumption!