QT & Phonon
 

Hi there,

Despite having read through hundreds of posts around here, I've never posted anything until now, so please bare with me if I'm being an idiot.

I'm sure this will come as no surprise to most people but I find the documentation for using QT on the N900 absolutely terrible (when it does exist), and in particular about using libraries...
I really like my N900, but I don't understand why Nokia seems to put so little effort into helping developers forward, after all I would have thought the whole point was to take advantage of the open source community to fill in the dead-empty ovi store...
At this point in time I haven't even set up my development environment, but I'm thinking about going about it this way http://wiki.maemo.org/MADDE/QtCreato...on_for_windows ; if anybody reckons there are better ways please let me know. The reason for not having done so yet is that I don't want to go ahead with something if it proves impossible.

Anyhow, to the point, has anyone used the Phonon library for QT, and in particular effects (audio, I'm not interested in video, yet...)?
If so I would like to know:

• what your experience in general has been with it?
• does Phonon come out of the box with the setup mentioned previously?
• what effects are available for the N900 (at the moment at least)?
• how do you go about using effects?
• what is the performance like, that includes the number of files that can be played simultaneously along with effects of sort (bearing in mind the application would also be running an interface, not just in terminal)?

Any feedback would be greatly appreciated,
Thank you!

Re: QT & Phonon
 

There is some information about Qt for Maemo5 in the wiki and for Qt 4.6, you have already for the beta a complete overview of all classes, which will be there, with examples and framework descriptions.


Giving out tech previews and keeping you up-to-date on the latest tools, giving you support directly of the developers, which are working on this, who look into packages and help people setting up their environment etc., proofs you wrong in my opinion. Maybe the information is a bit scattered, but we are trying to improve the things all the time.

Ok. First of all MADDE, which you have mentioned up there is bound to the latest software release, which is out there, which contains still Qt4.5 and not Qt4.6.

• Phonon in 4.5
• Phonon in 4.6

I will try to get you more information about Phonon. I used it once a while ago, and it was pretty straight forward. But please stay tuned, and I will get you more detailed information.

Daniel

Re: QT & Phonon
 

I have been developing a media player using QT + Phonon. It is overall very easy to use comparing with gstreamer in GTK. I think Phonon in N900 is backed by gstreamer but it is a higher level API.

Here are the effects currently available to N900:
speed
audiodynamic
audioamplify
audiopanorama
equalizer-10bands

Performance of audio playback without using effect is superb; with equalizer effect will cause the process running at 50% or more most of the time.

Re: QT & Phonon
 

Thanks a lot for this, I get your point about the documentation and I agree that it is mostly because it is all over the place. I'm not one to usually learn with books, but I would at least like to see some serious documentation. It's my first attempt at developing for a mobile platform and my first time using QT and I guess I'm just a little bit confused as to how I'm supposed to go about it.

I'm not sure I particularly need QT4.6 over 4.5 as of now, but I thought with PR1.2 coming I might as well use it. Can I upgrade QT fairly easily on MADDE?

On another note, I've been quickly following Symfonie, which seems to be based on QT4.6 and Phonon. I wanted to have a look at the source but it seems it's not available at this point in time... My main concern being that there is apparently a serious performance issue with the equalizer, which I suppose is making use of Effects, and I was wondering if this was a common problem. I'm planning on playing more than one file at a time, and possibly with more than one effect at a time too.

Finally (sorry if this is dragging), I'm still unsure whether to go for C++ or Python. I'm mostly worried about performance issues, if any. As far as I understand C++ should be faster than Python, but then if I use PyQT all the "heavy" tasks will be handled by QT regardless, am I right in saying this?

Thanks!

Re: QT & Phonon
 

this might be of help

Re: QT & Phonon
 

Pretty straight forward. But we just had a really small project.

Yes, as mentioned, just 4.5.

• what effects are available for the N900 (at the moment at least)?
• how do you go about using effects?
• what is the performance like, that includes the number of files that can be played simultaneously along with effects of sort (bearing in mind the application would also be running an interface, not just in terminal)?

[/QUOTE]

Phonon is just a wrapper for gstreamer. This means that the performance, latency is totally dependent on that, so that it is not possible to give Qt specific information here. Please follow for that the Maemo5 developer documentation and the gstreamer pages directly. But my advice would be to play a bit around with it, based on the Qt and gstreamer docs, and if you have specific questions, post them here and we try to help you out.

Daniel

Re: QT & Phonon
 

Good post, but the link in it is broken due to a newer version. Find the right version here.

Daniel

Re: QT & Phonon
 

The performance of equalizer is acceptable if that's the only application you run. Problem arises when you multi task. So when you have equalizer effect enabled and browse the net, delay to the audio playback is almost inevitable at current state.

BTW, symfonie source is available at:
http://maemo.org/packages/view/symfonie/

Re: QT & Phonon
 

Thanks for all these updates, I really appreciate all the feedback.

Code, I take it you're responsible for Symfonie :) (it seems we posted roughly at the same time)? I don't suppose you know if any of the effects listed handle stuff like Reverb, Delay, ... ?

Re: QT & Phonon
 

I coded symfonie but I have only used equalizer effect. Not familiar with other effects.