Trying to hack the RSS Channel

by C.K. Sample, III { Dec 1st 2005 at 8:00PM }

One thing we here at PSP Fanboy find frustrating about the RSS Channel feature on version 2.6 of the firmware is that you can only add podcasts via the PSP's built in web-browser. So we thought we'd try to hack our way in so that we can add our own feeds at will. Unfortunately, this is proving a tad bit more difficult than we originally thought. Until we crack it wide open, we thought we'd share our findings to date with you to see if anyone out there surfing around the wilds of the Internets could figure it out.

Mount your Memory Stick Duo on your computer and navigate to the SYSTEM folder. Inside this folder are the BROWSER and RSSCH folders. The RSSCH is the new creature that belongs to RSS Channel. Inside this folder is another folder called CHANNELS. Here you will find any image files (feel free to replace a few of them with images of the same size and format and with the same name, in effect customizing the look of your podcasts) that are associated with the RSS files to which you've subscribed and a file called CHLIST. If you crack open CHLIST in a text editor like pico you'll see that there are some basic flags before each bit of data that the PSP uses to find the podcast. Unfortunately, simply replicating this data around the information of the feeds you want to add doesn't appear to work. A file shows up in the list, but it is empty of information and fails to connect. I tried just replacing the URL on one of the working feeds with no luck. I tried editing in a hex editor, too. The PSP would seem to take the text of a valid RSS 2.0 feed, scrape it for the enclosure information, and then compile that text into the CHLIST file, which appears to be a binary. Now we just need to figure out how it does this and how to crack it.

Reader Comments (Page 1 of 1)

Techni @ Dec 1st 2005 9:24PM

Why not just use PSPs browser?

C.K. Sample, III @ Dec 1st 2005 9:26PM

Because I have to click each podcast one by one on a website to subscribe. I'd rather just load all my RSS feeds from my current podcasting app and be done with it in one fell swoop.

g.wygonik @ Dec 2nd 2005 12:07AM

ok - this one is easy ;-)

i'll stick with hex here...

note that "AA" listings are variable byte values. i used "AA" just as a placeholder. the real value in this byte changes based on the description given.

CSFF00010000 - always the same (or so it seems)
CHAN - start of a channel
AA - this byte is the total length of the CHAN section
000000 - three zero pads
URL20 - URL with a space (20)
AA - this byte is the length of the URL to the rss feed
000000 - three zero pads
[FULLY QUALIFIED URL TO FEED HERE - eg. with http://]
TITL - the title of the feed
AA - this byte is the length of the title
000000 - three zero pads
[TITLE HERE]
DESC - description text of feed
AA - this byte is the length of the description
000000 - three zero pads
[DESCRIPTION HERE]
COPY - copyright information of feed
AA - this byte is the length of the copyright info
000000 - three zero pads
[COPYRIGHT INFO HERE]
IMAG - name of image for display
AA - this byte is the length of the image name
000000 - three zero pads
[NAME OF IMAGE HERE]
CHAN
...

that's it. pretty easy to make an app to do this. but it's late and i need sleep.

btw - it looks like the PSP generates a unique name for the images to avoid conflicts. i renamed an image to "myimage1.gif" and adjusted the image name length byte and it worked fine.

_much_ easier than the project files for an Akai S5000 sampler ;-)

g.

g.wygonik @ Dec 2nd 2005 12:11AM

oh - the various section lengths ("AA"s in the above) do NOT take into account the three zero pads immediately following themselves. in other words, if the IMAG "AA" is 2B (43), there should be 43 characters in the image name AFTER the three zero byte pads - not including the zero pads.

gangsta_psp @ Dec 4th 2005 7:36PM

this is quite interesting. hope this works.

Jay Savage @ Dec 2nd 2005 1:54PM

Don't try to edit binary files in pico. Just...don't. Any text editor will corrupt your binary files eventually. And pico, which has a nasty habit of introducing hard line wraps (read: newline bytes) will bite you sooner than most, not to mention that printing non-ASCII characters to screen can produce *cough*interesting*cough* effects in the terminal. Use resedit or some other editor that's designed for the purpose, and keep a chart of the ASCII (or UTF-8, or whatever the PSP uses) bytes for the charaters you'll want handy.