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Train shedding

Filed under: Conference,Flumotion,GStreamer,Hacking — Thomas @ 3:57 am

2010-10-4
3:57 am

Had a good time at the OpenVideo Conference in New York City, as well as today at (cut short for me) FOMS.

I took the Amtrak train from NYC to Boston and was looking forward to doing four hours of hacking, knocking up a quick prototype of doing chunked streaming of Ogg and WebM.

I didn’t actually get to that point however because my test stream triggered the streamer going lost, meaning that its main loop is stuck. So attaching gdb I was reminded how the ‘pystack’ macro in gdb (which was incredibly useful – it prints a python stack) hasn’t worked for me for the last couple of years.

And this time I set out to properly fix it. If only the docs on gdb were easy to understand. My knowledge of gdb doesn’t go much beyond the standard ‘thread apply all bt’ stuff and doing simple inspection. I ended up understanding why the macro hangs (it compares the value of $pc to known function names, and goes up the stack until it finds PyMain. In most of my cases there is no PyMain however, and when you go ‘up-silent’ in gdb at the top of the stack, it just silently fails leaving you at the same frame forever).

I don’t claim to understand exactly how gdb works; for example, there are cases where $pc stays the same going up a frame, seemingly because a function is wrapped into a macro which seems to get its own frame. So I ended up writing a loop that goes up until the $pc changes, and then go back down, leaving me at the frame that calls a python method with a code object.

So, now I have my pystack working again in the cases I tested, so that’s good.

Incidentally, if anyone knows gdb well enough, here are some questions:

  • Is there a way I can detect in a script that ‘up’ didn’t actually go up ?
  • Is there a programmatic way to know how many frames there are, and what frame number you’re on ?

After fixing that, I was again bitten by a bug where – not always, but often – a flow with Vorbis and Theora has a timestamp/duraiton discontinuity of 1 nanosecond. I can’t reproduce it on the command line with -launch, so I think it’s related to a set_base_time call on the pipeline.

So I started writing a unit test, but for some reason make check in gst-plugins-base doesn’t work for me because it can’t find capsfilter and other core elements. So I get to dive into the test setup code again to figure out why a registry is getting generated that blacklists coreelements…

The train pulled into Boston as I was looking into how the new registry code works and why it blacklists coreelements, so I’ll have to save this test for a later day…

Incidentally, I have a day off in Boston this week. I really want to finally go to MIT and follow a class there, in computer science or mathematics. Is that sort of thing open in the US ? Can you just sit in on a class ? Any tips ?

Open Video Conference

Filed under: Conference,Flumotion,Hacking — Thomas @ 3:36 pm

2010-10-1
3:36 pm

The Open Video Conference here in New York has just kicked off, and Flumotion is streaming it live in Ogg/Vorbis/Theora and WebM!

I’m talking about HTML5 live video, Flumotion, Theora and WebM today, a little after 11:45 local time (NYC, -4 GMT), which is around 17:45 and later for the folks back home, in the second room, in the Amphitheatre. Make sure you use a recent enough browser that supports either Theora or WebM, like Firefox 4 Beta!

Feel free to vote for Flumotion

Filed under: Conference,Flumotion — Thomas @ 12:13 pm

2010-9-13
12:13 pm

If you enjoyed the world’s first live webcast in WebM/VP8 at GUADEC this year, you can send us a small thank you by voting for us in the streaming media awards. We think that our integration of WebM into Flumotion in only two days deserves recognition as being innovative and I hope you’ll agree!

I’ll be talking about this and other things at the Open Video Conference in New York first two days of October.

Tripping

Filed under: Conference,Flumotion,Life,Music,Travel — Thomas @ 10:42 pm

2010-9-6
10:42 pm

I haven’t done much work/conference travelling in the last months (I even skipped GUADEC, boo!), but it seems now is one of those months where random rears its pretty head again.

Right now I am at the other side of the world, in Sydney, a Holiday Inn in King’s Court (interesting neighbourhood…) This is late notice and I might not read my mail anymore, but hey, if you’re around and I know you, drop me a line. I was hoping to see Jan, GStreamer’s release ninja, here, but apparently he lives on the border of New South Wales these days…

I’m here for two and a half days, and then I fly back to Barcelona, and then to Belgium for my sister’s wedding where I am the best man.

My next trip is to the Open Video Conference where I’ll be doing a quick overview of Flumotion and HTML5. The conference is 1/2 of October, so I’ll be going to New York a few days before. I hope to go to FOMS as well for at least a day, but I’m also going to the Business of Software conference in Boston because, hey, we’re a software business! And it’s just around the corner from New York…

Further down the line there’s Streaming Media Europe in London on Oct 13-15, where I will do another presentation and assist in a panel.

And finally I hope to make it to the very first ever GStreamer conference on the 26th of October in Cambridge, but I really should get my act together and book a ticket for that soon…

Now I wouldn’t be me if I wouldn’t try and squeeze a concert into these trips.

So far, I’ve gotten a ticket to see the Walkmen play in Boston on the 7th of October. I want to get tickets to see the XX and Zola Jesus on the 2nd of October in New York, but I can’t make stubhub or related sites deliver tickets to Europe… Anyone in the US feel like joining me for that concert and receiving the tickets ?

It’s going to be a busy fall…

long life external batteries for laptops ?

Filed under: Question,Travel — Thomas @ 7:19 pm

2010-8-26
7:19 pm

I’m probably going to be doing some long flights pretty soon and I’d like to maximize my laptop time hacking on the plane.

Who of you have experience with big external batteries, what’s a good one to get, how long can I expect them to last and how long do they take to charge ?

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