[maemo-developers] [maemo-developers] Unresolved issues (Week 46)

[From: Charles 'Buck' Krasic]

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No, my dsp work was actually video related.    I did reuse Siarhei
Siamashka's mplayer code to decode/output mp3 directly, but that
obviously doesn't help with speex.

I'd suggest that the most practical approach for now would be to have
an application that uses a speex dsp task to decode speex,  and then
takes the output from that speex task and routes it to an existing
gstreamer plugin for pcm output.     This may be suboptimal, as the
data will cross the dsp gateway boundary twice more than necessary,
but it still might retain most of the benefit of offloading speex work
to the dsp.    I mean were talking something like 64KB/s of extra
copying in the worst case (?), which I don't think will be a very
significant cost even on the 770's OMAP processor.

The marginal benefit of persuing a zero copy solution (direct from dsp
to sound) just probably isn't work the effort.   Documentation for the
software components of the 770 that use the dsp is virtually
non-existent until now.   Aside from the mp3 decoder, I think all of
the other stuff has been basically unavailable to developers outside
of those working on Nokia's closed source multimedia applications.   
On the bright side, the gstreamer plugins for these various pieces has
been made open source in maemo 2.1.     I wouldn't hold my breath on
the dsp side of these plugins ever becoming open source (although I
would wholeheartedly welcome it!).

- -- Buck


Simon Pickering wrote:

>
>
>>> If you want something free, I'd suggest using our speex
>>
>> codec, which
>>
>>> is technically comparable, completely open, and has no known
>>> patent issues. We don't have an omap dsp implementation, but it
>>> has been ported to the various TI DSPs.
>>>
>>> http://speex.org/
>>>
>>> -r
>>
>> I did quite a bit of experimentation with the 770 dsp back in
>> late august. As a point of clarification, the dsp in the OMAP
>> 1710 (used in the 770) is just a TI *C55x, *which is already
>> supported by speex as far as I can tell. Thus, getting speex
>> to work on the 770 should mostly be an issue of adapting the he
>> exisiting speex C55x port to the build process using the free dsp
>> tools, or TI's code composer; and writing appropriate wrappers to
>> move data back and forth across the ARM to DSP boundary using the
>> linux dsp gateway interfaces.
>>
>
> There's still the problem of getting the DSP to output sound
> directly though, is there not? Or did you work out what the
> functions in the avs_kernel do (or bypass them completely)?
>
>
> Simon
>
> _______________________________________________ maemo-developers
> mailing list maemo-developers at maemo.org
> https://maemo.org/mailman/listinfo/maemo-developers


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