[mythtv] vps once again...

Michael T. Dean mtdean at thirdcontact.com
Thu Jul 22 19:23:41 EDT 2004

maestro wrote:

>i guess i'll subscirbe to the ivtv dev -mailinglist as i think thats the
>right place to get involved with the vbi/vps stuff in the driver, right?
Yes, but I would recommend signing up for the others, too.  The ivtv-cvs 
list never gets used (has had 2 messages so far), and the ivtv-users is 
relatively low-volume (264 messages compared to ivtv-devel's 12078 
messages).  That means that signing up for all three messages will 
result in only a negligible increase in messages, but prevent you from 
missing that one all-important message that's invariably on the list you 
don't receive.

>hm im not quite sure if i understand your last paragraph correctly (as
>i'm not a native english speaker)
I am a native english speaker, but that doesn't mean that my words 
always mean what I want them to mean.  (In other words, it's probably 
more my fault for not explaining things properly than your fault. ;)

>i'll try to repeat what you said in my own words.
>please correct me if i misunderstand something.
>mythtv doesnot support vbi with x50's since it uses the latest stable
>version of the ivtv driver and vbi isnt supported there.
Basically.  Although a user can choose to use any version of the ivtv 
drivers (I'm using ivtv-0.1.10pre2-ck100b, for example), MythTV was 
written to support users of the stable version of the ivtv drivers.

>so far so good.
>and the newer (unstable) version of ivtv is not used (yet). and new code
>(in myth) must not interfere with old drivers (e.g. render them
>if so what about the feature in the appearance setup page that allows to
>specify different resolutions for gui and video? this is only available
>if xrandr support is available in the x-window system. wouldnt that be a
>similar case? vps only available with ivtv driver-version > 0.1.9
>if vbi/vps support is in the newer version ivtv drivers as you said,
>won't theses drivers new capabilities (most important for me vps
>support) be added to mythtv in a near future release?
Yes.  This is true.  However, (and this purely conjecture based on 
interactions I've observed on the ivtv and Myth ML's), 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.  That doesn't mean that the primary Myth 
developers don't know about the other features available in newer 
versions of ivtv--many of them are subscribed to the IvyTV ML's.  As a 
matter of fact, many--including Isaac--have been known to contribute to 
the IvyTV ML's--in many cases to ensure that ivtv driver development 
proceeds in such a way that a 0.1.10 release will be compatible with 
current versions of MythTV while allowing future versions of MythTV to 
include new features.

In other words, Chris Kennedy has released hundreds of patches.  For 
example, the version I'm using is ck100b; Chris has released versions 
ck1 through ck10--without skipping any numbers--each of which has had 
several (up to 26) letter releases.  Throughout these releases there 
have been changes which make the drivers better, and changes which make 
the drivers worse.  For example, Chris actually has versions ck100c and 
ck100d available, but these are less stable and less functional with 
Myth than ck100b.  Knowing which version to use requires a lot of 
homework on the end-user's part, so Isaac, et. al., want to ensure that 
MythTV users can just install ivtv 0.1.9 if they're more interested in a 
working PVR than in actively following development of the ivtv drivers.

Also, among these driver releases, there have been many changes to the 
API (the calls other programs make to the drivers to interact with the 
cards), the tools (i.e. test_ioctl has become ivtvctl), the module 
options (i.e. the newest versions auto-detect everything--and 
surprisingly accurately, believe it or not), and more.  Because of all 
these changes, the MythTV developers want to ensure that before a 
feature is added to Myth, that feature will still be available in future 
versions of the ivtv driver and the means by which that feature is 
accessed will remain (relatively) constant (so we don't have 
MythTV-0.15.1-ck100b releases :).

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.

>p.s. mythtv missed the last 3 minutes of C.S.I. yesterday, because of
>the unpreceise timings given by orf (austrian broadcast company) and
>that would be no problem with vps support, so i said to myself
>"something has to happen". i hope i'm able to do it, if its not allready
I'm sure many others will be indebted to you for the work you plan to 
do.  After all, CSI just isn't CSI if you don't hear Grissom's final 
one-liner and see him shaking his head in bewilderment as the 
perpetrator gets dragged away by the cops.


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.

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