[mythtv] MythWeb Flash

Jean-Philippe Steinmetz caskater47 at gmail.com
Wed Apr 25 06:26:21 UTC 2007

On 4/24/07, Chris Petersen <lists at forevermore.net> wrote:
> Jean-Philippe Steinmetz wrote:
> > First, while I agree with you its important to keep this as open
> > source as possible there is a clear distinction that needs to be made
> >  between the Flash IDE and Flex.
> Actually, neither of these has anything to do with open source or not.
> The only reason I'm hesitant to recommend something designed with
> Adobe's tools is that they're not freely available to the majority of
> people.  I also thought that Flex was an xml-based file format used by
> Adobe, not some other application.
> With that said, I honestly don't care what environment these tools are
> developed under as long as there are files that I and others can access
> later to make any minor edits as necessary.  This is why I suggested
> Ming or OpenLaszlo as alternatives, since they would let linux users
> access the source files without having to purchase/install both Windows
> and any Adobe applications.
> I know that there is an xml-based format used by Adobe, and if that is
> compatible with Flash/Flex, it would be a good alternative that allows
> small tweaks from within Linux, but still give access to the
> higher-level functions provided by the full Flash IDE.

I'll be more specific. Adobe Flex as a technology that allows Flash
developers to strip away the Flash IDE. When building a Flash application
you have a *.fla file (binary file format), which is responsible for
managing all artwork assets, some code, and external linking to other files
that will publish into a single swf. Using Flash as an IDE you can put all
of your program code in plain text files with the extension *.as but you
will still need a *.fla to compile everything into a *.swf file. Flex
technology offers the same Flash technology but differs in that it strips
away this need for a *.fla file. Instead, *.fla is replaced with a *.mxml
file which is (as the extension suggests) xml based that essentially does
everything the *.fla does in terms of linking and setting up the Flash
application. Now the tricky part to the Flex product line is that there are
two forms of Flex, Flex Builder and the Flex SDK. The Flex SDK is a freely
available set of tools that merely let you compile *.mxml based
applications. Flex Builder is an Eclipse-based development environment for
the Flex SDK. So by using Flex, you can achieve your goal of having a Flash
solution that does not rely on any purchased Adobe product in order to
modify and compile. Also, since the Flex SDK is written in java 1.4 you can
compile from any java supported platform.

> What I will suggest in this regard is to develop a Flash player
> > that's art is controlled via template which can be changed at
> > runtime.
> This seems to be the standard way to do things, and I agree that it's a
> good idea.  However, I'm concerned by what you say about having to
> product the artwork via the Flash IDE.  For instance, I'm pretty sure
> that flvplayer.swf allows online specification of theme image files for
> dynamic control of its appearance.

While it is perfectly possible to pull in image files and apply them in
whatever fashion you want, this method is typically not used for Flash
development. Flash/Flex is a vector based graphic systems and so by using
rastered images you lose a lot of the advantages of using Flash in the first
place in terms of artwork. For this I suggest a bit of a compromise, where
the player is capable of using both raster images as well as vector (swf)
images. To make this happen will probably require two different templates be

> 2/3. In Flash, an FLV player is an FLV player. The difference between
> >  a live stream and a pre-existing file is simply a parameter you
> > would send the player. Parameters can be passed in to swf via HTML or
> > URL reference so you can use the same swf file to drive the two
> > sections.
> Like Kormoc said, MythWeb already has rudimentary support via ffmpeg for
> streaming recorded programs to an flv player (I just don't have an flv
> player I can include with the code).
> Eventually, the backend itself (or some related app) will do the
> converting/streaming, which is what will give us access to the LiveTV
> stream.
> -Chris

 My concern here is how these streams are facilitated. The first (and
easiest to use) requires that an FLV file pre-exist and a URL is given to
the player which then can progressively download and play the file. I have
never tried it, but I do not believe that accessing an flv file that is
currently being written to will work very well for FLV playback in this way.
The second mode is FLV streaming. FLV streaming can only be accomplished via
the RTMP protocol. The RTMP protocol is a proprietary technology developed
by Adobe, however there is some work to reverse engineer this. Red5 is a
java-based os project that is working on this. Using RTMP will require the
use of an additional server daemon that will need to interface with MythTV
as well as the Flash client. I am still familiarizing myself with Red5 but
this could be a very good option for making streaming of live-tv work.

- Jean-Philippe
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