Encoding videos to watch on the N900 with low battery consumption
 

Hi.

It seems that the last messages in theads like http://talk.maemo.org/showthread.php?t=26457 are quite old (almost 3 years old) and, as things have progressed, the answers may now be different.

In particular, I would like to know what would the recommended settings for videos for an N900 updated with PR1.3 (not with the CSSU yet, but with kernel-power v47 and able to overclock up to 1100MHz) would be a good compromise for watching lectures (say, like the current courses from stanford or iTunes U) and battery life.

I mention lectures because I am willing to reencode the videos and I can drop the framerate for those to about 20fps or even 18fps, as long as the audio is OK (I'm not a native English speaker and the quality of audio interferes with my understanding).

As the N900 has a DSP that can decode some stuff, what format would be better suited for it? MPEG-4 ASP, H.264, Theora, or VP8 would give me better battery/be easier to decode?

Also, what is the DSP more specialized in decoding: MP3 or AAC or Vorbis?

And what about the container? MPEG 4? Matroska? Anything else?

Any hints about resolution/bitrates?

I can use, say, Handbrake or mencoder on my Debian machines. That's not exactly a problem.

I see that not all containers are well implemented from Felipe Contreras blog (regarding gst-av), and I have some extra codecs installed from the repositories.

So, given this situation, what are your experiences? I am sure that many others may benefit from a compilation of such information.

Ideally, I would like to create 2 or 3 presets for Handbrake (and attach them to the post) so that they can serve as starting points for other people.

Well, that's it.


Thanks for any feedback and experiences.

Re: Encoding videos to watch on the N900 with low battery consumption
 

I believe you should target h264 baseline profile, 800x480 max resolution, keep it under 4000kbps on the video side, AAC audio stereo, mp4 container.

Re: Encoding videos to watch on the N900 with low battery consumption
 

Hi, @jflatt.

First of all, thank you very much for your reply, and it is indeed appreciated.

But I have one question: given equal bitrates, and resolutions, what would be easier for the DSP to decode? An MPEG-4 ASP file or a H.264 baseline profile?

I am focused on maximizing the battery while I play the videos, as I may not have an easy power source during some times (and, of course, I would be being gentle on the heat of the device etc.).

I am willing to use a binary blob for decoding stuff, from what I saw mentioned in the kernel-power thread, if that reduces power consumption.

Guidance regarding what to choose is appreciated.

Re: Encoding videos to watch on the N900 with low battery consumption
 

I believe encoders have a fast decode option, this results in a lower quaity picture as a result, should in theory consume less power in the process.
Also the N900 can play video for a long time if you can plug it into an external screen, through the TV out, and then lock the phone; as most of the power goes into illuminating the screen, not decoding.

Re: Encoding videos to watch on the N900 with low battery consumption
 

I don't believe it does MPEG4 hardware decoding. Try out a short clip both ways, watch the processes in 'top'.