Comments on: n900 Battery Duration: Ogg vs. MP3

By: tuomas

tuomas — Mon, 28 Dec 2009 23:12:31 +0000

Probably not in any time soon. I don’t want to include it, if it doesn’t support everything in the current (1.0.5/6) version.

I could try to find the files (ffmpeg and gstav) I used for the ffvorbis tests and put those somewhere available, if people want to try them out without proper packaging.

By: Flandry

Flandry — Mon, 28 Dec 2009 22:46:54 +0000

Hi Tuomas

Will ffvorbis be showing up in ogg support package any time soon?

By: Seppo

Seppo — Mon, 14 Dec 2009 20:45:20 +0000

Thanks for interesting experiments. In headset mode I think sample rate conversion from 44.1 kHz to 48 kHz causes still some PA load. Using HW native 48 kHz results to slightly lower load.

Sample rate conversion in music encoding phase could also increase a bit the quality if the converter is of good quality.

By: tuomas

tuomas — Wed, 09 Dec 2009 15:52:53 +0000

@Dave: Yeah, I didn’t mention the Ogg being much better than mp3 because it’s hard to measure :)

Based on the DSP binaries in /lib/dsp/ I would guess that all audio decoding is done on software only.

By: Dave

Dave — Wed, 09 Dec 2009 15:36:34 +0000

Is it worth mentioning that Vorbis is a more efficient encoder than MP3? I’ve seen listening tests that claim 80kps vorbis is equal to 128kbps lame (both VBR) and that 96kps is better than 128kbps lame. That’s a 25-40% difference in filesize at those (lower) rates, which I’d imagine translates into power saving. I know these things are difficult to objectively control but I’d suggest it’s worth mentioning at least.

AAC is held to be equal to Vorbis, but it is more complex than MP3 and so should eat more power (unless they’ve done fancy DSP things to compensate).

By: tuomas

tuomas — Sun, 29 Nov 2009 12:11:54 +0000

What the pulseaudio is actually doing? It takes less cpu with headset connected but still quite a lot.

By: pupnik

pupnik — Sun, 29 Nov 2009 11:01:09 +0000

Pulseaudio looks to be chewing up 15-25 (peak) percent CPU. Some ideas to help this.

0) Take a hard look at pulseaudio and see what functionality can be disabled/optimized.
1) Allow apps to disable xprot and eq if they limit speaker volume to 70%?
2) Allow apps to tell pulseaudio “I have pre-eq’d audio”. This means ogg or mp3 playback can be equalized at almost no cpu cost, before transforming the frequency-domain data into time-domain.

Ah i had another thought but it fled…. it fled into the void.

By: tuomas

tuomas — Sat, 21 Nov 2009 08:47:22 +0000

@Mans: I compiled version 745e506 and got roughly one hour longer battery duration with the new ffvorbis compared to the one I used in my original tests.

By: tuomas

tuomas — Tue, 10 Nov 2009 12:52:39 +0000

@Flandry: I think I need to keep the libvorbis there as well as many games etc. use that. One choice would be to include the current libvorbis and its gst-plugin in the future as well but with a lower rank so that ffvorbis/gst-av would be used automatically instead of the libvorbis. I guess the ffvorbis has an API of its own.

@Mans: Hmm.. I need to verify the exact SVN version I used somehow. I remember FelipeC saying that the FFmpeg got some NEON improvements back then and I think I took a version after that.

By: Mans

Mans — Tue, 10 Nov 2009 12:30:30 +0000

The NEON FFT was added on 2009-09-10 with SVN rev 19806, and further improved over the following days. This optimised FFT made Vorbis decoding 3x faster, so it would be interesting to see if that further improved the battery life.