how do i get off this list
On Oct 7, 2007, at 8:43 PM, Stéphane Doyon wrote:
On Sat, 6 Oct 2007, Daniel Weck wrote:
On 6 Oct 2007, at 04:21, Stéphane Doyon wrote:
-Increase playback speed without affecting pitch. I'm not
starting from
scratch here, I have something more or less working, only the
integration
into Rockbox is still somewhat rough.
As part of my programming work in the context of self-voicing user
interfaces,
What sort of work would that be exactly? That's OT though I guess,
so perhaps privately...
I have used 2 open-source implementations (GPL I think) of
"timescale modification" algorithms.
Could you give me references? I'm aware of Soundtouch.
Stéphane, what algorithm have you been playing with ? (WSOLA ?)
Err what's that? Looking it up. Hmm yes, that's it :-). Gives you
an idea of what a strong theoretical background I have on this
subject :-).
What I'm using now is a previously unreleased implementation by
Nicolas Pitre <[EMAIL PROTECTED]>. I've helped him with a bit of tuning
and a bug report or two, but the credit really goes to him. He
implemented that from scratch. He worked from a good understanding
of the algorithm, although I'm pretty sure he did not read that
paper :-). We both used that implementation for a few years on our
Linux'ified iPAQ H3600 handhelds, to speed up talking books. Those
have a StrongArm processor running at 206MHz, which is relatively
modest. Since I was familiar with Nicolas's implementation and I
knew it did not require too much CPU power, I naturally used that
when trying to speed up playback on Rockbox. Nicolas said he was
happy to release his implementation under the GPL, so integrating
it into Rockbox officially is quite possible.
My current integration of that implementation into Rockbox is
rather rough. I do intend to post it as a patch soon. Then I'd need
help from some dsp.c guru to fit it in properly. One difficulty is
that this algorithm needs a relatively large sound buffer to work
on, a latency of about 0.1s, and this would be the first Rockbox
DSP effect to have this kind of requirement AFAICT.
The good news is it works for me on an X5 and an e200. Audio books
are typically lower bitrate and mono, and those I can speed up to a
factor 3 without problem. High bitrate music can also be
accelerated to some degree, just not as much. My rough integration
causes latency in the UI when speeding up high bitrate files to
near the max capacity of the CPU. But for audio books, it works
well. I haven't measured the effect on my battery life, but I've
been using this for a while and I know that qualitatively, the
effect is not disastrous.
I have not done a thorough comparison of this implementation vs
Soundtouch, or other implementations. I did do a quick subjective
comparison with Soundtouch: for speeding up speech, Nicolas's
algorithm appeared to sound a bit superior, while for slowing down
music, Soundtouch was better. I must admit that this works well
enough for me that I am not really motivated to further investigate
alternatives.
-See if we could implement DAISY, or a subset of it, by
preprocessing the
DAISY on the host machine and coming up with a cue sheet for each
DAISY
level. We'd need to have a playlist backed by multiple cue sheets
and the
ability to switch between them. I'm not entirely sure this makes
sense,
would need to look into it more seriously.
Right. I think that would be a good start, as it would be easy to
implement using existing Rockbox features.
However, I would like to offer blind/visually-impaired users the
convenience of using their standard Daisy 2.02 or even 3.0 DTBs
(Digital Talking Books), without conversion.
I imagine that would be more convenient, and probably acceptable as
long as things like XML parsing happen in a plugin. Although
personally I don't see preprocessing on the host as a big
limitation because it would be near instantaneous (unlike video
conversion for example).
2) text support: well, I think this is unnecessary to start with.
When we've
I agree.
3) the ability to play Daisy books from a plugin: my test
implementations so
I'm not sure about this one. Why play from a plugin? Or is this
just a step in your development strategy.
Admitedly I an not familiar with the newer versions of the DAISY
standard and may be missing some issues.
--
Stéphane Doyon
<[EMAIL PROTECTED]>
http://pages.videotron.com/sdoyon/
