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How the formats .wav + .flac + .m4a (alac) effect battery life on portable daps

post #1 of 8
Thread Starter 

I am curious if .wav files will actually make the battery last longer since the processor has much less work to do reading an uncompressed wav vs a much more complex lossless compression flac?


Basically what's the battery usage for each type? Is it true a .wav uses less cpu cycles so it uses less battery?

post #2 of 8
But wav and Flac files need the player to read more data, less CPU cycles vs. more data to read: who knows?
post #3 of 8

I use a Clip+ with Rockbox. I think you'll find that generally the extra strain required to read and playback formats with (relatively) complex compression (.ape,.mp3 ect) has a larger effect on battery life. However, with players with larger batteries that are more powerful I doubt there would be much of a difference.

Edited by Willakan - 8/31/11 at 10:10am
post #4 of 8
Thread Starter 

cpu's almost always use way more energy then mass storage device. So i think saving cpu cycles will have a much bigger effect on saving energy. Especially with solid state memory

post #5 of 8
you should also consider hard drive based storage. A large file will take up more space, thus requiring more reads/movement from the disk. a larger cache will be needed to play the same amount of audio (length of time) and that would also degrade battery life.

EDIT: here's a thought though. the CPU clock cycles are usually constant in a small player as they are small, efficient processors taht dont need to step down their processor speed. Regardless of what kind of file you are playing or even regardless of wether or not you are playing a file, your CPU will be constantly running. The actual battery drain would come from performing mathematical operations on data, not from the CPU clock. Just clarifying
Edited by shrimants - 8/31/11 at 9:33pm
post #6 of 8

from my experience,,the kbps is what count the most.  flac and wav files will take more battery than mp3 or other lossy format.  i tested both lossy and lossless files in my dap and the battery life improves considerably with lossy data.  but again,the SQ is compromised.

Edited by plonter - 9/1/11 at 1:38am
post #7 of 8

I can not say for sure but I would consider the higher bitrate to make the largest difference, not only will more system resources such as RAM and storage be needed but the higher bitrate will tax the CPU more then any compression algorithm could possibly do. 

Besides, FLAC and WAV are both types of compression, so I don't really understand what you mean by comparing it to MP3, sure FLAC is lossless compared to MP3 and the like but it is still a form of compression, unless we are talking about an uncompressed PCM stream then every format is a form of compression.

To get down to the small details, a bit is obviously the smallest form of data.  So 320Kbps, or 320,000bits is not going to require as much CPU throughput as say 1400kbps or 1,400,000 bits of data per second.  That isn't even mentioning upsampling and the extra bit depth, they will all stress the system further, it is actually the same as asking if 3GPP @ 320x240 288kbps is going to use more power then AVCHD @ 1920x1080 24mbps, that is an extreme example but some food for thought. 

I would also like to mention that CPU cycles are not what uses the most power, take my 1090T for example, it has 6 cores clocked @ 4.2GHz, and it is constantly clocked at that for stability.  Assuming it is idling it will use around 30watts, and the voltage is also constant, so 4.2GHz @ 1.475v.  So what is the factor that gets a system to consume power, CPU cycles are one thing but not the main factor.  Once stressed to 100% load, the cycles remain constant, the voltage constant but the power usage increases to over 280watt, that is thanks to the current ;)

In computing, with all power saving features disabled, the only thing that will increase power usage is current drawn.

post #8 of 8
the only way to be sure is to do your own benchmarks. whilst codec A might last longer than codec B on player X, that doesn't mean the same is going to be true on your player Y. the firmware could be better tuned for certain codecs than others. i know the difference between flac and lossy codecs is negligible when using rockbox on my sansa clip v2. but that is totally contrary to the experience plonter had above.
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