Implementing QtMultimedia

[Harri Pasanen]

On 07/02/2012 09:04 AM, BogDan wrote:
>>>>   Hi,
>>>>   >
>>>>   >Quick questions:
>>>>   >
>>>>   >Does NDK provide sufficient APIs to implement QCamera and
>>>>   >QAudioInput/QAudioOutput, or is some detour via Java required?
>>>>   >
>>>   Short answer is yes and no:)
>>>   For a longer answer please
>> checkhttp://mail.kde.org/pipermail/necessitas-devel/2012-May/000900.html
>> andhttp://mail.kde.org/pipermail/necessitas-devel/2012-May/000913.html  threads.
>> Ok, thanks.   Looks like that discussion addresses mostly video and mp3
>> playback.   I'm actually more interested in capture, both audio and camera,
>> (photos and video), and also lower lever apis, getting at the raw data before
>> any codecs are involved.    I think there has been some OpenCV using projects,
>> but I guess nothing merged to android-qt?
>>   
> It is (almost) impossible to get the raw data before, it is impossible to decode it that fast :)
> I try it myself and I failed :), anyway you can use my findings to look further, maybe I
> missed something ...
> BogDan.
>

For images, typically you'll get a frame from the hardware for the 
viewfinder in lower resolution that is usable for preview purposes, and 
fast enough to manipulate in software, at least for still images.    For 
that only issue is color conversion, and for Neon there exists fast 
assembly code to do that.

For audio, I'm hoping to get raw PCM (wav) data from microphone. For 
that speed should not be a big issue, depending of course what it to be 
done with the data.  Getting something like the spectrum demo in Qt 
sources running would cool.  Also QAudioOutput is pretty useful for 
games and such.

Nokia themselves had issues in implementing these though, so I expect 
there may be complications, even if on the surface it would seem 
straight forward.   I believe I read somewhere that Android suffers from 
audio latency issues, as does the future Windows 8 phone.  Only one 
getting it right seems to be iOS, AFAIK.

Harri