Ivtv and VPS/PDs (was Re: [mythtv] vps once again...)

Michael T. Dean mtdean at thirdcontact.com
Fri Jul 23 14:56:28 EDT 2004

maestro wrote:

>>... until ivtv 
>>releases a "stable" 0.1.10 version (i.e. a version that is intended for 
>>general use by all end users, for distribution by packagers, and for use 
>>as a basis of development in other projects), MythTV is being developed 
>>for use with ivtv 0.1.9.  
>i know it belongs to the ivtv mailing list
So let's move it over.  I'm actually on both lists. :)  (Make sure you 
don't Reply All.)  (For ivtv-devel users, the beginning of this thread 
can be found at http://www.gossamer-threads.com/lists/mythtv/dev/77650 
.  Quick summary:  Manuel (maestro) is considering implementing some 
VPS/PDS support in MythTV using the PVR-x50 with Hans' recent VBI/VPS work.)

>but you seem to have (a little) insight there:
Like I said, only observations from reading the lists--mainly just 
catching you up on "history."  (If anything I say is wrong, someone 
please let us know.)

>do you have any infos when such a stable release will happen,
Hans tried to get development to stabilize for a short term to get an 
ivtv-0.1.10pre3 release out, but the card didn't seem to like the 
schedule.  ;)  I haven't heard anything more on it lately, but I can 
almost definitely say there will be a 0.1.10pre3 before 0.1.10 final 

Getting 0.1.10 final out (with all Hans' 
auto-detection/auto-module-loading work) would be very nice since most 
problems are related to users incorrectly specifying the module options 
or incorrectly loading the modules.  However, I think (pure speculation) 
that Hans may be waiting *because* of the auto-detection 
code--occasionally, a user will report a new card that isn't properly 
autodetected, so when these reports die out, he may resume work on 
getting a pre-release out.

>and won't it be 0.2 since in the readme states 0.1 isn't developed
>actively anymore. (i think that interferes with ck's efforts doesnt it?)
Well, Kevin Thayer is working on 0.2--which is basically a ground-up 
redesign of the entire driver (something that every software development 
project should do at least once).  It sounds like it will do some great 
things, but it takes time.

Chris Kennedy has been trying to get the existing/working (0.1.10pre2) 
drivers to provide professional-quality video capture/editing support.  
He basically works on it at work, then goes home to work on it for fun 
(and, maybe sleeps for 15 or 20 minutes a day ;).

Hans Verkuil has been working on autodetection, autoloading, VBI, radio, 
PCM capture, and other "additional features" of the cards (i.e. beyond 
just video encoding/decoding).

And many others are working on testing, miscellaneous fixes, etc.  
(Sorry if I missed anyone who feels he/she has done enough work to 
warrant an "introduction."  Feel free to introduce yourself to Manuel. ;)

All of the work being done by Chris/Hans/everyone else will still be 
useful for the 0.2 drivers.  After all, the hard part is finding out how 
to make things works.  As a matter of fact, getting back to the 
redesign-from-the-ground-up idea, figuring out how things work on 0.1.10 
will allow Kevin, et. al., to use the lessons learned from the 0.1.10 
effort to ensure that the features are "designed into" the new drivers 
as opposed to just "bolted on."  In other words, not knowing how 
something works makes it more difficult to design for that feature--you 
might start down one path, and, by the time you get things working, 
realize that there was a better way to add the feature.  Although you 
can then change the code to use the better way, doing so may introduce 
bugs or leave some unnecessary code lying around.  Therefore, figuring 
all this out before 0.2 will (IMHO) help to make 0.2 a better driver.

>>So, for all practical purposes, ivtv-0.1.9 is the most current driver 
>>version available because all other versions are development versions 
>>not intended for general use.  So, if you can create VPS support that 
>>has no effect on users of the 0.1.9 drivers (not to mention users of 
>>non-ivtv-based cards) but that just works if the VPS data is available 
>>(possibly with a switch to enable/disable VPS support), you might be 
>>able to convince the main developers to include that patch in the main 
>>branch.  Otherwise, you might have to wait for ivtv-0.1.10 (or ivtv 
>>0.2.0).  Also, I think the BTTV cards support VBI, so in theory, if you 
>>write the VPS code generically enough, it can be used for BTTV cards and 
>>for PVR-x50's.
>hm it seems as if the vbi support in the newer ivtv drivers is already implemented.
>i posted a msg on the ivtv list on this topic and awaiting answers.
>so if it would be (re) implemented to work with 0.1.9 and mythtv it
>would probably only live until ivtv > 0.1.9 is released, (because it
>will then be supported by the driver) the mythtv - changes may persist
>if they work with the new drivers or will need to be reimplemented. that
>sounds like doing work twice doesn't it?
Since ivtv 0.1.9 has already been released, any changes made to it would 
be similar to the ck patches--they would be development versions, 
because they wouldn't be the "officially sanctioned" stable release (as 
a matter of fact, Hans has some patches for 0.1.9 - 
http://www.xs4all.nl/~hverkuil/ - which add at least VBI support, if not 
VPS support).  Also, I'm pretty sure that VBI/VPS support requires 
changes to the 0.1.9 drivers, so implementing it at the user level (i.e. 
MythTV) wouldn't be possible.  Therefore, trying to ensure VPS support 
in 0.1.9 is not possible.

Instead, you'll probably need to ensure that the code you add to MythTV 
does not interfere with users of 0.1.9 (i.e. if no VPS signal is 
detected, your code doesn't do anything).  Also, it's critical that your 
changes do not require users to upgrade to a newer release version of 
the ivtv drivers--that they can continue to use drivers without VBI/VPS 
support.  If you can accomplish these two things, and if you also write 
the code so that it can be extended for use with the BTTV drivers (or 
even better, so it works with the BTTV drivers), you'll probably be able 
to get your changes into Myth (and make a lot of people around the world 
very happy).

>>BTW, you'll make many more friends on this list if you reply to a post 
>>by adding to the bottom (bottom-posting) or by responding to parts of a 
>>post "inline" as I did.  And, it's always a good idea to trim the 
>>extraneous material from previous messages.
>thanks for the hint. i'll try to bear this in mind for my future
>postings (guess this one's ok?!)



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