I think the main problem we have with Phonon is that it is an abstraction
level higher than what we need. It's more oriented around playing files for
you.
It does seem to support a raw-data output via AudioDataOutput, but the
description itself says it's not for realtime use:
"Although it is not designed for realtime performance, the latencies
associated with accessing the data should be low enough for applications
that provide visualizations of the data. This class can also be used to save
the audio data for further processing."
Beyond this, another deal-breaker is that the most precise way to refer to
time offered by Phonon is milliseconds. You seek by saying the millisecond
you would like to seek to.
RJ
On Tue, Dec 14, 2010 at 9:04 AM, Adam Davison <adamdavi...@gmail.com> wrote:
> I think from a user point of view DirectX/CoreAudio would be a
> preferable choice to Quicktime. For Windows users (i.e. most of our
> users) Quicktime is a large additional download (O(100MB)). Quicktime
> is fairly intrusive on windows too, generally slow, takes over all
> your file types, installs stuff that sits in the system tray the whole
> time and other unsavoury things like that (at least the last time I
> tried it). I think we'll make a lot of people angry if we force them
> to install Quicktime.
>
> Of course there is the pragmatic problem of the fact that most of our
> developers are linux/osx and know nothing about DirectX...
>
> I would suggest that someone takes a more serious look at the current
> state of Qt's Phonon stuff on Windows before implementing a Quicktime
> layer.
>
> For linux we can use the distribution provided copy of libmp4v2 (or
> ffmpeg if someone is feeling particularly enthusiastic/masochistic).
>
> Adam
>
> On 14 December 2010 13:13, Tobias Rafreider <dj.raffi....@googlemail.com>
> wrote:
> > Hey all,
> >
> > Quicktime is my preference for portability. It solves AAC playback and
> > licensing issues on both OS X and Windows (I guess). The drawback is
> > that Linux users won't be able to use M4A out of the box. Maybe we
> > hazard the consequence.
> >
> > If we decide to use Quicktime and Albert can provide an initial
> > implementation for OS X I am willing to "port" it to Win. Ideally, I
> > will refactor the code such that we load Quicktime dynamically by using
> > the QLibrary interface. If quicktime.dll on Windows is not available, no
> > AAC playback is possible. We do same for MP3 recording and streaming via
> > lame.
> >
> > Alternatively, since we have stable AAC code via libmp4v2 it might be
> > possible to refactor the plugin code. If [libmp4v2.dll |libmp4v2.so] is
> > available M4A playback is possible. I do not know if the plugin code
> > works that way. But, there are a lot of libmp4v2.dll files available via
> > google. It would be rather simple for our community users to activate
> > AAC. Recall that AAC is a heavily requested feature in our forums.
> >
> >
> > Thanks,
> >
> > Tobias
> >
> > Am 13.12.2010 19:32, schrieb Albert Santoni:
> >> Hey Tobias,
> >>
> >> Yes, we could also use Quicktime or a native API like DirectShow.
> >> Unfortunately, I'm going to be stuck with only my Macbook for the next
> >> month, but I can still try playing with the Quicktime Audio Extraction
> >> API:
> >> http://developer.apple.com/quicktime/audioextraction.html
> >>
> http://developer.apple.com/library/mac/#samplecode/SimpleAudioExtraction/Introduction/Intro.html
> >>
> >> The ExtAudioFile API itself wasn't bad - once you have stuff
> >> initialized, the basic decoding functions (read/seek) were
> >> straightforward to use. This API also supposedly exists on iOS, which
> >> is a bonus. :)
> >>
> >> I think making Quicktime a requirement on Windows for AAC playback is
> >> not outlandish, so I can try to play around with that.
> >>
> >> Also, if we do manage to get a couple of these native or near-native
> >> backends working, I'd be willing to convert them into pure C++ (no Qt)
> >> and roll them into a library. We can't be the only people who need
> >> cross-platform, low-level audio decoding using native APIs that don't
> >> carry any legal baggage. (Distributing an MP3 decoder with your
> >> application made more sense in the Windows 98 days.)
> >>
> >> Thanks guys,
> >> Albert
> >>
> >>
> >> On Mon, Dec 13, 2010 at 4:31 AM, Tobias Rafreider
> >> <dj.raffi....@googlemail.com> wrote:
> >>> Hey,
> >>>
> >>> great job. Could we also use Quicktime API to decode AAC/M4A on
> Windows?
> >>>
> >>> Tobias
> >>>
> >>> Am 13.12.2010 11:36, schrieb Adam Davison:
> >>>> Hi,
> >>>>
> >>>> Just to say this is excellent and exactly how we should be doing it...
> >>>>
> >>>> What happened to phonon in qt 4.7 in the end, have they managed to
> >>>> expose audio data yet?
> >>>>
> >>>> Adam
> >>>>
> >>>> On 13 December 2010 06:55, Albert Santoni<albe...@mixxx.org>
> wrote:
> >>>>> Hi guys,
> >>>>>
> >>>>> Tonight I wrote a SoundSourceCoreAudio class that plays M4As using
> the
> >>>>> system provided decoder on OS X. It uses the "Audio File Services"
> API
> >>>>> (ExtAudioFile), which is part of AudioToolbox, which is part of Core
> >>>>> Audio. We can freely distribute this as part of our main Mixxx builds
> >>>>> without worrying about M4A patent issues because we're using Apple's
> >>>>> decoder, which OS X users have already paid for.
> >>>>>
> >>>>> Special thanks to Apple's super crappy documentation and endless
> >>>>> layers of redundant APIs. I spent more time trying to figure out
> which
> >>>>> API to use than actually writing code.
> >>>>>
> >>>>> Seeking and metadata decoding (using TagLib) work fine. I've only
> >>>>> tested with 44100 Hz / 16-bit files, but if it doesn't work with
> other
> >>>>> formats, it shouldn't be difficult to fix.
> >>>>>
> >>>>> Code is pushed to:
> >>>>> lp:~mixxxdevelopers/mixxx/features_coreaudio
> >>>>>
> >>>>> Enjoy,
> >>>>> Albert
> >>>>>
> >>>>>
> ------------------------------------------------------------------------------
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