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Latest Project Blogs
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 Blog archive
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 16th May 2008
As the site does not provide links to view archived blog entries, I've prepared an archive with all the blog entries linked using permanent links. I also have the contents stored locally, will probably make it public as well, for easier browsing.
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Resampling filters design
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 13th May 2008
I've designed -60 dB and -80 dB resampling filters today. The first one is 48-tap one (and more when downsampling), is oversampled 32 times, so the half-width table has 768 coefficents. The second, high quality one is 64-tap and is oversampled 128 times, which yields 4096 coefficents in the table. Both filters have 3 dB attenuation at 0.45 of sampling frequency and respectively -60 or -80 dB at 0.5 of sampling frequency. I've also made siginficant progress on resampler reference (not optimized at all) code, but it is not yet finished.
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audio.output progress, audio resampling
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 12th May 2008
I've done some more work on new audio.output class version. It has a complete subthread framework including command passing. The thread opens AHI, in case of failure, object fails gracefully as it should, with error reported.
I've also started work on a variable rate audio resampler. It uses bandlimited resampling concept described by J. O. Smith. I've started from designing three resample filters, for three levels of quality. The first, low quality filter is ready. It has 257 coefficents in total and spans over 32 input samples (if no scaling is used). The filter ensures both aliasing distortions and filter interpolation distortions are kept below -40 dB.
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Another busy day
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 7th May 2008
I've made some more changes to http.stream bumping the revision to 51.8. I've added missing attributes, cleaned up the docs, simplified subthread initialization and shutdown code. I've also added a feature allowing applications handling HTTP permanent redirections properly. MMA_StreamName attribute may be queried after object construction, and if there has been any 301 redirection, the attribute contains a new URL. Then an application can update its links.
I've fixed a nasty bug in gif.decoder then. It caused 0x4 location read on every GIF image decoded. Just three missing letters in a function call.
Then there is another bugreport pending, for audio.output this time. Subthread initialization code is broken, so if for any reason subthread fails to initialize, calling application will crash. I've decided to reuse extensively tested http.stream subthread framework. This is work in progress currently.
BTW my Ph.D. thesis is two pages longer since today :-).
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http.stream 51.7
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 6th May 2008
After almost total rewriting of the class I've finished in finally. The most troublesome thing has been automatic redirection on 3xx server response. It requires that current connection is closed and a fresh one is made with newly generated request. While testing it, it also turned out that some HTTP servers do not comply with RFC 2616 and send relative pathes in "Location" header field, while the protocol specification clearly states it must be absolute. A workaround for this issue has been added.
Anyway it is finished (except some cosmetics) and in my opinion it is a very nice component not only usable as a media stream source for Reggae. An application can use it standalone to fetch any resource available via HTTP GET request. The programmer does not need to have HTTP or socket API knowledge. As http.stream gives easy access to (parsed) HTTP request and response headers, an application can use some advanced features like cookie handling, range requests, conditional requests and more. Automatic redirection makes it easier too (as it is standard feature of any WWW browser, we usually don't even know that it happens, but handling it in own application is a headache, believe me). The new class is on the MorphOS CVS server and probably will not be released separately before the day 11111 (the mysterious date of MorphOS 2.0 release).
Christian Rosentreter reviewed MediaLogger 1.8 and sent me a bunch of style guide and GUI consistency notes. Most of them have been implemented, and MediaLogger 1.9 is on the way to be released publicly at the usual place.
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Old code, new code...
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 26th April 2008
Glueing an old code and a new code always lead to troubles. The same in http.stream. I've added network thread code and response header parser. After fixing some obvious compiler errors and warnings, I've got a ready executable, which... crashes. My limited time allowed me only to localise the crash in the source code. I will attempt to fix it on Monday.
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Still messing with HTTP
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 24th April 2008
HTTP request header generator is almost finished. Network code and response parser will be taken from the previous version. Redirection resolver loop is ready as well. That means, new http.stream will be ready tomorrow (or in a few days). New nice features are: working automatic redirection, user agent spoofing, and passing custom fields to the request header (this last feature allows for example for supporting cookies).
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http.stream revisited
Project: Reggae on Efika (Multimedia)
posted by Grzegorz Kraszewski on 23rd April 2008
On demand of application programmers I'm in a process of rewriting http.stream. Most important thing is really working atomatic redirection (in response to HTTP 3xx codes). There are also new features like custom request header fields, User-Agent spoofing and some minor enchancements. Network errors handling is improved. The work is not yet finished, I expect to release the new class before the end of May.
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New Symphony OS Released
Project: The Helios Thin Client (Hardware)
posted by Alexander Drummond on 11th April 2008
Symphony OS
ISO is x86 for the time being, but we obviously have PPC versions of Symphony OS. Hopefully we'll release an ISO for both platforms on our next release.
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The Delay
Project: Remote Aid Deployment System (Other)
posted by Denis Hilliard on 3rd April 2008
Apologies for the delay from the announcement of some screenshots for the app. I will make up for the delay however :P
Hope everyone had a good easter,
D. Hilliard
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