<DIV>FYI, I just did some channel changes with my DirecTivo and it takes 2-3 seconds from the key press to when the new video starts. That's about as good as you can expect with digital video because to change an mpeg stream you have to wait for an I-frame and fill up the decoding buffer and that takes time. There's just no way you can change channels as fast as you can with analog. If you have a digital cable or satellite box that's separate from the DVR then you have potentially a decode, an encode, and another decode, so 4-5 seconds doesn't seem out of line.<BR><BR><B><I>Chris Delis <chris@delis.net></I></B> wrote:</DIV>
<BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid"><BR><BR>On Fri, 14 Nov 2003, Chris Delis wrote:<BR><BR>> On Fri, 14 Nov 2003, Michael Janer wrote:<BR>> <BR>> > Why is it that SageTV can do this channel change with a PVR 250 or 350 at about the same speed as a Tivo? I would imagine the engine in mythtv can be sped up in some way. Sagetv has a client server setup also and seems to be able to make the channel changes pretty decent ~1 second. I imagine if SageTV can do it with java and windows, Mythtv should definately be able to do it.<BR>> <BR>> <BR>> First of all, it has nothing to do with the recreating the ringbuffer! :-)<BR>> (Willy and Isaac's posts on myth-dev set me straight on that!)<BR>> <BR>> After perusing some code a little (experts, please correct me if I'm<BR>> wrong... I'm just trying to learn/understand and _not_ complaining :-),<BR>> it seems that the thread communication in
mythfrontend is a little laxed<BR>> in handling state changes (probably done on purpose because it simplifies<BR>> development, not as many semaphores/mutexes/etc to deal with, which<BR>> means less chance for deadlock). For instance, in libmythtv/tv_rec.cpp,<BR>> I notice a few busy-waits here and there such as:<BR>> <BR><BR>Blah blah blah... <BR><BR>Please ignore my last email where I was babbling about busy-waits, etc.<BR>in mythfrontend (tv_rec.cpp). The only delay that would cause is<BR>in the responsiveness of the GUI (length of time between sending the<BR>"channel up" event and the GUI responding to it). This does add to the<BR>overall delay in channel changing, but it is probably not that important.<BR>I'm guessing most users don't _really_ notice the hangtime until _after_<BR>they see the OSD pop up.<BR><BR>I will quit now! (while I'm still behind ;-)<BR><BR>Cheers,<BR>Chris<BR><BR>_______________________________________________<BR>mythtv-users mailing
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