Battery life - a suggestion

[maggot_brain]

Hello everyone,

it's been a while since I've posted on the forums but I have a little suggestion for the people who are writing the documentation.  How about a little 'Optimising Battery Life' section?  I'm by no means a supergeek but do have some software and hardware knowledge.  As far as I can see the key to preserving charge is to prevent the HDD from being used too much and the CPU from working too hard.  The problem is that I am not familiar enough with Rockbox internals to know what settings to tweak.  Apparently what WPS you use is also an issue.

Apologies if this has been posted before but it seems like a good idea.  I must admit though that I've only read the X5 manual.  Rockbox for my DAP is getting to everyday usability status it seems and I'd like to know what can be done to get the most of out my battery.

Thanks to everyone who has helped in developing Rockbox.

Ananda

[saratoga]

Improving battery life is mostly a matter of optimizing the codecs people are using.  Its not really something you can tweak.

[Llorean]

Well, choosing the a more efficient codec or encoding at smaller file sizes, making sure your "Limits" are set to the smallest values that still work for you, and enabling disk power down, as well as having a simple, non-animated WPS without album art can all make *some* difference.

[baobab68]

Not to mention turning on the directory cache option..that makes a big difference if you are navigating the file tree.

[Llorean]

Yes, but Directory Cache actually worsens your battery life if you're the kind of person who, like me, just launches a playlist when he turns on the player, and doesn't navigate almost ever. So it's very dependent upon your use habits.

[Rincewind]

the biggest issue is disc power down. This can increase battery life by a few hours. The other settings (apart from dircache) don't have much effect in my experience.

Also, using your DAP on a Hifi-system increases battery life because the player doesn't have to provide current to drive the headphones.

Another small thing is the pre-buffer option. Decreasing the prebuffer has the effect that the disc has to spin up less.

In short: everything that makes the disc spin up less is good. The disc and the codec are the main parts that consume power. Tweaking anything else is not very important.

If you have an iriver and put the firmware in flash, the dircache can hibernate, so then dircache shouldn't have a negative effect on battery at all.

[riksweeney]

If you have an iriver and put the firmware in flash, the dircache can hibernate, so then dircache shouldn't have a negative effect on battery at all.

How do I do that?

[Rincewind]

If you are confident in your skills to follow instructions exactly, go here:
http://www.rockbox.org/twiki/bin/view/Main/IriverFlashing

I don't want to scare you, it is rather easy, but there are a few things you have to care about, so read everything on this page!

With flashing, the boot time is decreased dramatically and you don't see text messages from the bootloader at startup, it starts at the rockbox logo.

[baobab68]

My ramblings on battery life as it relates to disk spinups and dircache...

The firmware flashing feature is only for iRiver H1xx's at the moment, am I correct?

Rincewind, I too am curious what you mean about it being able to hibernate!

Also Llorean, out of genuine interest, does Directory Cache use more power because it takes a little while to build/check each time you boot up (I can live with that if it's once per listening session), or does it use more power because it has to maintain the Cache in RAM and uses processor cycles to manage it?

In terms of the battery life consideration, I have also noticed that with longer playlists, when I press the REC button once to display playlist contents, RB will spin up the disk. For shorter playlists, it doesn't. I guess this is a function of how much of the playlist can be fit into RAM?

(I see Rincewind has replied in the meantime to the flash question, I'll read that page)

[nls]

Dircache might lessen battery time because it uses ram that otherwise would have been used for buffering songs so the disk must spin up more often. But as Llorean said it depends on your listening habits. In other words, if you navigate the file browser a lot it might help battery time and if you listen without much navigation it might lessen battery time a bit, it also depends on the number of files how much ram is needed.

I don't know about your playlist question, it sounds to me like you are using an unofficial build wich I am not familiar with.

[baobab68]

I originally mentioned that I was using norbu's build from over at MR, but I think I edited that out when I was trying to make my post more clear, sorry about that.

[Rincewind]

My ramblings on battery life as it relates to disk spinups and dircache...

The firmware flashing feature is only for iRiver H1xx's at the moment, am I correct?

I have a 120, I don't know if it works for H3xx series as well. This should be mentioned on the wiki page.

Rincewind, I too am curious what you mean about it being able to hibernate!

Hibernate means, that with firmware in flash, rockbox knows if the player was in usb-mode or not after the last dircache scan. If the contents of the disc haven't changed via usb, then dircache doesn't need to scan the whole disc at boot, it reads the dircache from flash instead -> less disc access at boot.

Also Llorean, out of genuine interest, does Directory Cache use more power because it takes a little while to build/check each time you boot up (I can live with that if it's once per listening session), or does it use more power because it has to maintain the Cache in RAM and uses processor cycles to manage it?

I don't think that the few cpu cycles matter much. The only thing is, with dircache in RAM you have slightly less codec buffer, but I haven't tested how much this matters.

(I see Rincewind has replied in the meantime to the flash question, I'll read that page)

Hm, I answered you question anyway (I should read to the bottom first, then post  )

The Rec-button to view playlist thing looks like you are using my patch, but I don't think it has something to do with it. Other people can test this behavior when they go to context-menu->playlist->view current playlist. I can't say something to that question, I don't use long playlists.

[Llorean]

Rincewind: Dircache will still have the negative effect of using some of your Audio Buffer to store the cache in while Rockbox is active I believe.

[Rincewind]

Yes, I mentioned that, too. But I don't think that 500kb of about 30MB Buffer matter that much. If you save two or three disc spinups by using dircache, then it possibly already paid for itself. And it makes navigation faster, too.

[Llorean]

Well, you said "If you have an iriver and put the firmware in flash, the dircache can hibernate, so then dircache shouldn't have a negative effect on battery at all." and this is untrue if it doesn't save any spinups. If you have resume on startup enabled for example (say if you're Me and just listen to a full playlist of your whole collection) then Dircache does have a negative effect.

And how much difference it makes depends on how much RAM you have free, for example someone on an H110/115 has less available to use.