On 7/31/06, <b class="gmail_sendername">John P Poet</b> <<a href="mailto:jppoet@gmail.com">jppoet@gmail.com</a>> wrote:<div><span class="gmail_quote"></span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Since capturing firewire video data on my backend machine resulted in<br>a constant stream of discontinuity errors, I turned my frontend<br>machine into a combo backend/frontend, and hooked the firewire up<br>there.<br><br>
On this frontend machine, I am able to capture pretty clean video via<br>firewire. However, if I try to watch anything while it is recording<br>via firewire, the video is very jumpy, and I get a lot of "video is 30<br>
frames behind audio" type messages. This is on a Athlon X2 4200,<br>runing <a href="http://2.6.17.7">2.6.17.7</a>.<br><br>I figured that it had been long enough since Jim Westfall submitted<br>his ieee1394 dma patch that it would be a part of
2.6.17, but I<br>discovered it was not. After applying his patch:<br><br><a href="http://www.gossamer-threads.com/lists/mythtv/dev/187783#187783">http://www.gossamer-threads.com/lists/mythtv/dev/187783#187783</a><br><br>
and building a new kernel, the video playback while recording problem<br>is now solved. I did have to "hand" apply the patch because the<br>formatting of the dma.c file in 2.6.17 has changed slightly. Applying
<br>this patch caused the CPU usage of mythbackend to drop from 10-11% to<br>3-4% while recording via firewire.<br><br>Unfortunately, I now had an audio problem. The sound would drop-out<br>for a fraction of a second, every couple of seconds. This only
<br>happened if I was recording via firewire at the same time. I figured<br>my firewire port and my sound card must be sharing an interrupt, but a<br>quick look at the motherboard manual disproved that theory. I then<br>
check the latencies of those two devices (lspci) and discovered that<br>both were at 32. After adjusting both up to 64 (setpci), my audio<br>problem is also solved.<br><br>I still have a little problem with channel changes. The channel
<br>change program I am using works 100% of the time, when I am testing it<br>via the command line. With Myth in control it only seems to be 75%<br>reliable. This program changes channels on my SA3250HD via firewire.<br>
<br>I figured that to get 100% reliable channel changes, I would switch to<br>lirc. I have an ir-blaster and decided to hook it up along side my<br>ir-reciever. Unfortunately, both are serial and therefore use the<br>lirc_serial driver. It turns out the lirc_serial driver cannot handle
<br>two serial ports at the same time. Furthermore, you cannot run two<br>lirc_serial drivers at the same time. To get around this, some people<br>have hacked the lirc source tree to create a lirc_serial1. This is<br>actually much harder than it sounds, and is generally a royal PITA. I
<br>may try a little harder to get channel changes to work via firewire...<br><br><br>John<br>_______________________________________________<br>mythtv-users mailing list<br><a href="mailto:mythtv-users@mythtv.org">mythtv-users@mythtv.org
</a><br><a href="http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users">http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users</a><br></blockquote></div><br>Wow, great post. I am going to look in to the patch that you mentioned and try your fix for the audio problem b/c I am having the same thing. Let me know if you want a copy of my sa3250ch file because I don't have any problems. Thanks for taking the time to post.
<br><br>Allan<br>