From: Mark Allums <mark_at_allums.com>
Date: Sat, 28 Jun 2008 23:58:18 -0500

Erik Ramseth wrote:
> I searched for a good amount of time but I could not seem to find any
> reference to the efficiency of Ogg Vorbis decoding versus the
> efficiency of MP3 decoding. I am mostly concerned with overall
> playback time for similar quality files. Is there any data available
> on this subject (even generic rockbox info, not specific to the c250)?
> What about from a theoretical point of view... should MP3 decoding or
> Ogg Vorbis encoding be more efficient?
>
> If not, I suppose I will run some tests soon.
>
> As a related question: what are some settings that will greatly affect
> battery life in general (I would guess things like EQ, dithering,
> replaygain, and SD card usage have a detrimental effect on battery
> life, but that's only an anecdotal/experiential statement.... no facts
> to back it up).
>
> Any info would be appreciated.
>
> Thanks.
>
> --
> Erik Ramseth
>

Ogg Vorbis files tend to be smaller for the same quality than MP3, so I
would generally call Ogg more "efficient". A smaller file takes less
memory, takes less time to load, etc. However, I can't speak to the
energy usage of the algorithms. In my experience, they are roughly
equivalent, battery-life-wise, but your mileage may vary.

The size of the prebuffer would affect the battery life a bit on hard
disk players. A bigger buffer would allow the disk to spin up less often.

Any setting or plugin that uses more CPU cycles would make the battery
life lower.

An SD card wouldn't affect battery life significantly.

Any setting that causes a bright LED to light a lot, or any usage of a
backlit LCD screen will use up battery.

Higher volume uses battery. Different earbuds/headphones could affect it.

Older batteries don't last as long, even if they have never been used.
If you replace your battery, try to get one with as recent a manufacture
date as you can find.

Unnecessary charging/discharging will lower the battery's run-time over
time. A lot of people make that mistake. Lithium ion batteries should
not be completely discharged before charging. They can and should be
charged at any time. Some lithium ion batteries should be fully charged
and kept that way, others do better, (useful lifetime-wise, not
run-time-wise) at 60-80% of full capacity. Alas, I have never been able
to discover which is true for my Sansa e270. (The nickel metal hydride
batteries in the Toyota Prius are never fully charged. They stay
between 40-80%.)


Mark Allums
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Received on 2008-06-29