Hi

I am running in a problem and have been trying to resolve it now for some days. Now its getting on my nerves as I am not sure if its a hardware issue or a software bug.

After a long setup time I am now so far that I am receiving a decent >80% signal (I used http://www.xmission.com/~pchdtv/forum/v ... .php?t=688 to find the signal strength). I can record and view HD & SD (I hope thats the correct abbrv) content.

*However* the HD content plays with a cyclical delay:
-play for 3 secs
-~.5 sec delay
The SD content has sometimes problems with the audio, the video is not hanging, the sound is cutting in and out.
I tried recording & playing but I get the exact same result as watching live tv.

I used the URL above to record the data stream raw from the dvb driver. Using mplayer I can decode and display that stream without any delay. It works fine, except that mplayer won't size it to the screensize. No problems with the audio either.

One thought was that maybe Myth had extra work as it tried to fit the content to the screen. I tried running 1920x1080i and found out that Myth just did not want to run any video anymore (record & live), the displayed start picture was also sized wrong (2 times too high). mplayer hung also at that size (first picture was shown but that was it).

Gets me back to:
-is it maybe the issue that is being discussed under the jerky playback, ie Myth needs perhaps 1Gb mem?
Everyone I ask in person says 512 MB should be enough, I would rather save that money and spend it on an additional HD or another capture card.
-is it perhaps the lame Jetway VIA motherboard? Regular video seems to work, Myth does not crash (too much).
-some told me to switch back to an older KnoppMyth version where the PCHD3000 card was still supported in as it might give better performance. That would not explain why the playback under Myth has the problem and mplayer not.

Anyone has any ideas how to solve this problem?

I tried using Xine as DVB player, it worked but had also some tough times to work itself through the data, that might be a Xine issue.
I also used different (and none too) sound cards to make sure it was not some kind of sound buffer problem in the card.
I tried KnoppMyth R15.1 and R16.

Pentium 4 3Ghz 800FSB with hyperthreading
512 MB
JetWay PM800
PCHD3000
120Gb
Onboard Via audio | SoundBlaster Live | Revolution 7.1
nVidia FX 5200
Audio Authority video VGA video converter

your proc should be enough and I have the same proc and run with 512Mb ram with no problems. Have you checked the DMA on your HD? Do you have the nvidia binary drivers installed?

You should be able to run 1080i if your tv supports it with that setup and that converter as I use the exact same thing, though you will have to use the older nvidia drivers as 1080i has been broken for a couple of versions now.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

I am not too familiar with the DMA settings. hdparm -i on my hd shows that I am using udma (udma5), no regular dma or mdma. Its a Seagate Barracuda, ST3120026A, 7200 rpm, I think its sufficient. Maybe I am not understanding the question.
I have to admit that I am just using the standard installed (I assumed nVidia) drivers from the KnoppMyth install, it sounds like I need something more.


That would be my goal, looking at all the pages that show how to create a modeline I only came to 940x540. Now knowing its possible to actually get the video to work under 1920x1080i I will definitely check into it.

to check dma run a command like
hdparm /dev/hda
(substitute drive letter for hda)
in the resulting output you want to make sure that dma and 32bit io =1
the default install of knoppmth does not install the nvidia drivers. you need to run
install-nvid<tab><tab>
there are two versions on there now. You will need to use the 6629 drivers if you are wanting 1080i.
I believe I have posted my XF86Config file somewhere in the hdtv section of the forum, and it has a couple of 1080i modelines in it. If it's not there let me know.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

You made my July 4th weekend Xsecrets!
I thought that when I would re-install the nvidia drivers were installed by default (since the fx 5200 seems to be the most popular card and the speed was already much better as the ATI card I had before in it).

Everything was correct for the DMA (with a read ahead of 256, not sure if thats important).

I will scan the site for your config file to get 1080i running better but in the mean time I can finally watch HD.

Is it normal that the video stutters at the very first second of the playback?

Thanks again!

yeah it sometimes studders as it gets going, but should be good from there on.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

Most of the channels I want to view have no problems anymore.

The biggest problem is with the ABC HD channel, though its signal strength is over 80% it requires to stop the back end, restart the back end and then start the front end each time I want to view the channel, ditto to switch afterwards to another HD channel, this is only with the ABC HD channel (71 in my case). Not doing so blurs the entire ABC channel or mutes the other HD channel I switch (after watching ABC HD).

Small thing is that the HD feeds seems to be faster as playback (which I know is not possible), could it be there are some slight delays independent of the hardware? Seems to only happen with the HD channels.
The feed seems full speed though, maybe its the times when its scrolling (ie when the camera shoots over a landscape) where the processor can't keep up?

I solved a problem I had with PBS (choking/stuttering) by using the TS solution you posted one time (choosing TS instead of PS in the DVB setup). Again, using mplayer and the DVB directly (http://www.pchdtv.com/forum/viewtopic.php?t=693) there was no problem, surprised I need to choose TS but ok.

This seems to have been resolved to either by clicking the hardware mpeh support or the TS choice in the DVB setup.

The only thing left:

Anybody else run into this before? If there is no workaround does anyone know if there was a build where this was working correctly?

Thanks!

At a guess it's low on memory... Try running "top" in another window while playing the problematic HD recordings and watching the memory usage... Use capital M in the top window to toggle sorting by memory usage. I'm beginning to suspect that there may be a memory leak in MythTV 0.18.1since I've seen some similar issues. There's even another HD performance thread where someone traces the playback glitches down to the swap daemon running...

Thanks for the 'top' hint to check out if there is something running and taking away the cpu time. It also showed it was not a CPU issue (its powerful enough, there is minimally 8% left).

I noticed that the free memory of course slowly ran out but it was mostly set free again once I changed channels.

For sure looking at the numbers when changing to the trouble channel and to other channels afterwards did not show that I was running low on memory or that it was non stop swapping.

I did find out that for most cases I don't even need to end the frontend, I can just exit to the menu and view the channel again. Most of the time (when there is just jerkiness in the screen before) the channel will run fine again.

From your post I also take a hint that it might make sense to install an older version and see if this issue appears too.
--edit
This weird behavior only occurs at 1 channel, re-reading my last post I really wonder if there is some kind of variable that does not get 'cleaned' in some cases and causes all this trouble, quitting the entire display and starting it again does perhaps force a clean of the variable in question.
--edit2
R15.1 had the same behaviour, I recall the video effect (not the blurring but the effect after switching back to another channel) from transcoding experience, some issue with the fps. Video and Audio stay in sync because part of the video is moving fast and then runs very slow.

I think you may be jumping to conclusions giving things a clean bill of health via top. I should probably have warned you that because of the way it samples and displays things it won't doesn't show you everything that's happening. What it can tell you, which should be taken as a warning, is the sustained load and memory usage. If you see the CPU/Mem usage go over 90% or the loadavg go over 2 it's time to start being concerned.

Also as I've described in other threads around here (rather than repeat myself I'll ask you to search) the issue with real time stuff like video playback is latency and getting a big enough slice of time when you need it. That gets much harder as your CPU usage goes up, especially with a general purpose scheduler. Realtime systems often use special schedulers to make sure that critical tasks get done within a certain window.

Hmm, one of the easiest ways to find out if memory is the issue is to get more memory. I might need to give that a try.

The only reason I am thinking its actually a bug/abnormality in either the video stream or viewer is because I have no problems switching to other channels, just that one channel.

Your description about real time systems can explain the problem but it would mean the problem would occur with more channels.
BTW I expanded the packet size (in the mythtv-setup) to twice the size.
This results in an also longer time to switch a channel but the problem kept occuring.

I will try the extra memory and maybe see if I can compile the tip of myth and see if that helps.

well the explanation could be that only one channel in your area broadcasts in 1080i. I believe that is the case in my area. most are 720p. and 1080i takes more resources memory/cpu/etc. to decode.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets

I was thinking about this just myself before checking up on the forum! A quick google over the websites (and recalling a conversation I had with someone who 2 months ago) show that ALL HD channels here are in 1080i, there is only 1 in 720p and thats the one that confuses the Myth viewer when I change to it.

If 1080i takes more memory in and 720p does not and I can switch without any issues between 1080i channels then could this still be a memory issue?

wow how unusual. you are the first person I've heard say their market is all 1080i and only one 720p. which market are you in?

It may not be a memory problem, but since that is the only channel on a different format it may well have something to do with the format. what output resolution are you using. if you are outputting 1080i then 720p would have to be scaled to fit, which could be causing the problem. I haven't experienced this issue, but we could have some direction knowing it's the only channel that's different.

_________________
Have a question search the forum and have a look at the KnoppMythWiki.

Xsecrets