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Subject: Re: GSOC application question

Re: GSOC application question

From: Michael Sevakis <>
Date: Sun, 30 Mar 2008 20:48:23 -0500


Sorry I missed the PM earlier. I see from the IRC logs you got some
specifics about it. You can look in apps/dsp.c at dsp_downsample and
dsp_upsample to see what is desired to improve upon. Those functions are
used for both the pitch shifting and resampling files not sampled at 44.1KHz
to 44.1KHz. The ARM and Coldfire processors use their respective assembly
versions of the C functions.

Besides a better resampler, a potential feature that has had much interest
in the recent past is time and pitch stretching to allow playback at a
different tempo or key - one set independently of the other.


----- Original Message -----
From: Laszlo Szilagyi
To: Michael Sevakis ; Rockbox development
Sent: Sunday, March 30, 2008 7:25 AM
Subject: Re: GSOC application question

On Sun, Mar 30, 2008 at 1:33 PM, Michael Sevakis <>

Dear Laszlo Szilagyi,

One item that has been discussed much is the implementation of a high
quality resampler for the Rockbox DSP. While the linear interpolation
algorithm is fast and perhaps nescessary to use in certain circumstances for
certain CPU-hungry codecs such as the SPC emulator, most find it less than
satisfactory in general for reasons I have no doubt you understand.

Rockbox needs a better resampler than that is both frugal on CPU cycles
(this can depend on the target's processing power) and qualifies as
high-quality output.

Your qualifications and interests indicate you would be a good candidate for
this project. It would be great if you would consider it as a possibility.

Michael Sevakis (jhMikeS)

----- Original Message -----
From: Laszlo Szilagyi
Sent: Sunday, March 30, 2008 5:16 AM
Subject: GSOC application question

Dear Rockbox!

I'm an electrical engineer student in my 4th year from Hungary (BUTE),
studying mainly about embedded system design, digital signal processing, and
of course the programming tools in connection with these fields. I've heard
about the "Google Summer Of Code", and the projects Rockbox offers caught my
attention. As my main specialization is digital signal processing, I'm
mostly interested in tasks covering this field. I like the

Realaudio Support
DSP Plugins
Better Video Support

tasks at first sight, but before I send my application I would like to know
if my qualification is sufficient for the various tasks. Of course I'm open
to some embedded work as well, but what I really like is the DSP... :)

My studies/experiences:

- programming in C/C++ language (in C++ I'm familiar with STL, and design
patterns, used doxigen)

- DSP knowledge: mathematical fundamentals, filter design, real time signal
processing on hardware (in this semester my "Labor work" is about fixed
point multi rate filters (for radars), last semester with one of my college
we created a "Larsen effect" cancelling system on an Analog Devices Blackfin
eval board, and it actually worked... :) )

- Matlab programming knowledge (experience with (multi rate) filter design,
simulations, also with fixed point simulations)

- Linux user and programing experience (till the end of this semester I'll
accomplish a course called "Linux programming", which will give me more
insight of programming the system)

- FPGA programming (experience: realization of a Discrete Cosine
Transformator, simple "VGA card" and pong game :) )

- Atmel AVR (assembly, C) and ARM7 (eCos, C) programming experience

I'm open to study new fields, interested in multimedia.

With this background what can you recommend me, before I create my
Thanks your help!


Laszlo Szilagyi

Dear Michael Sevakis!

The resampling project you mentioned interests me, my current "labor work"
in this semester is partly about resampling (a digital down converter design
and implementation on FPGA, using CIC-filters and CIC-compensating FIR

Would you give me a more specific definition of the project?


Laszlo Szilagyi
Received on 2008-03-31

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