

Justin.TV launches an iPhone live video broadcasting app - abstractbill
http://blog.justin.tv/go-live-with-justin-tv-for-iphone-2-0/

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abstractbill
I had the privilege of leading the team that created this app, and wrote a
fair amount of the code myself. If you have any questions about the app, its
development, or just anything at all relating to justin.tv on the iPhone,
please feel free to ask.

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chopsueyar
What iDevices support this (video 'broadcasting')?

What H.264 encoding is used (profile, level)?

What bitrate do you aim for? Is it different for 3G vs 802.11g/n?

What framerate/resolution?

Thanks for the opportunity to ask!

~~~
abstractbill
_What iDevices support this (video 'broadcasting')?_

iPhone 4 and 3GS. The iPhone 3G didn't have a hardware video encoder, if I
recall correctly, so we disabled broadcasting on it and anything lower (though
viewing works just fine!).

I _think_ we also tested on the latest iPod Touch and found everything worked.
I'd have to check my notes to be certain though (sorry, not in front of my
work laptop, looking after my 1-month-old daughter right now!).

 _What H.264 encoding is used (profile, level)?_

Would definitely have to check my notes for this. I'll follow up.

 _What bitrate do you aim for? Is it different for 3G vs 802.11g/n?_

The OS gives us a limited degree of control on this one. We get to specify the
bitrate as "high", "medium" or "low" and it appears to be completely
undocumented what each one maps to, if they're the same for each device, etc.
In practice it looks like "low" is always around 80-120kbps, "medium" is about
800kbps-1.5mbps and "high" is somewhere north of 4mbps. We use "low" and
"medium" depending on how much actual network bandwidth we think is available.

 _What framerate/resolution?_

Resolution depends on the camera - we don't modify it away from the native
resolution. So far, either 480x360 or 192x144 depending on device and selected
camera.

Same is basically true for framerate. So far every camera I've tested has
given us 26fps.

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houseabsolute
> we don't modify it away from the native resolution ... 480x360 or 192x144

The iPhone 4's camera is 1280 × 720 though . . .?

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abstractbill
Yes, sorry - I should have said those resolutions are what comes out of the
hardware video encoder, rather than the camera.

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chopsueyar
Is 480x360 a hardware imposed limit, or was that your guy's decision?

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stevederico
Does/Could this app locate or detect a user is at a particular event?

If Justin.tv could sort by event, other users could watch events like
outsidelands music festival and flip through all the different view angles of
the concert.

I understand event based results can be found by searching, but the idea of a
collection of event streams intrigues me. Just an idea..

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chopsueyar
This is a really cool idea!

Especially, if you have justin.tv sponsor an event, and get the majority of
users to download the app and start broadcasting.

The app should be able to send approx. GPS position, and the server can create
an event "channel" with all the related streams (based on GPS).

App should have a location-disable option too.

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Tautologistics
This is another step closer a device I have been thinking about for many
years. Imagine having a silent witness to any incident one gets involved in
where it is one person or group's word against another. This device would
record audio/video/time/location and send that data, real time, to a remote
server that can timestamp and saved it. Police brutality, a bar fight, war
crimes, an auto accident? Even if the cameras/phones are confiscated, stolen,
or destroyed, the truth has already been set free and there is no way to cover
it up.

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modeless
Isn't broadcasting live video expressly forbidden by AT&T's 3G TOS?

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jrockway
justin.tv didn't sign the AT&T TOS.

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modeless
Actually, since they are US-based iPhone developers, they did, but that's not
even the issue. Users of the app would be breaking the TOS.

I don't know about you, but as a consumer I don't like it when companies
insert BS clauses they have no intention of enforcing (or worse, selectively
enforcing) in their TOS. Not that anyone here needs more convincing that AT&T
sucks...

~~~
jrockway
Shoot first, ask questions later.

