For someone just starting out, KnoppMyth and this forum are invaluable resources to set up a MythTV box. To give back in a small way, I want to share my experience setting up a box with KnoppMyth. My goal was to record shows for viewing later and on other PCs. I am not interested in paying a monthly tithe to the cable company or one of the satellite providers, my setup is OTA. Since I get a lot of ghosting and other interference, I wanted to use digital vs. analog. I purchased a $50 Air2PC R0.2 HDTV capture card on ebay. I do not have a HDTV capable set (recall I am too cheap to get cable), but on my 10 year old 60" Pioneer rear projection screen the picture is awesome compared to analog.

PC config
P4 2.8GHz, 512MB
ATI X600
Air2PC R0.2
ATI Remote Wonder

Install steps I took:

- KnoppMyth R5A30 has support for the Air2PC R0.2 card
- Boot the R5A30 install CD

*EDIT*
- *important, CRITICAL, step originally forgotten*
_-at some point (preferably when your ethernet connection is up) you need to get the card firmware
___- Get the firmware from here: http://www.linuxtv.org/cgi-bin/viewcvs. ... 1&view=log Sorry this link is broken right now due to the merging of the DVB and V4L projects. I have not be able to find the firmware since.
___- click the download link, and get the .fw file onto your myth box
______-I have a web server available, so I put it in an easily accessible place and used wget my.web.server/dvb-fe-bcm3510-01.fw
___- cp dvb-fe-bcm3510-01.fw /lib/firmware
___- you now need to reboot
___- setup will resume if you hadn't started
___- you can add the file after myth is setup, reboot and then run myth-setup again, follow instructions below
*END EDIT*

- Follow standard install instructions until mythtv-setup
- in mythtv-setup
___1. follow standard instructions
___2. Capture Cards - set up a DVB card, use defaults
___3. Setup a video source
______- Log into your zap2it account select only the digital channels if you only using the Air2PC card
___4. for [DVB: 0] set your Video Source to the one configured in 3
___5. you will now be able to scan for channels
______- I can not emphasize enough having a good UHF antenna setup. I spent hours getting my antennas aimed properly, and amplifiers wired correctly. Any splitters or amplifiers used for OTA must be rated for 50MHz- 900MHz for the standard UHF channels. This can be very helpful: http://www.solidsignal.com/manuals/AntInstallGuide.pdf More on what I did to follow.
______- Once the channel scan is complete, check to see that the channels found are expected. Look for any you think are missing and note them. You also need to go back into "4. Input connections" and set the starting channel to one of the channels found during the scan. Set it to the number listed in (), for example 51.
______- The channel scan may pick up stations you will never be able to get a strong enough signal to view
______- The channel scan may miss some perfectly strong signals (re-running scan will find them)
___- exit mythtv-setup and let install finish (follow standard instructions)

- Once the system reboots
- Get the ATI card running (search the forum for instrucitons on this)
- you *may* be able to watch live TV.
- if live TV works, you are probably in pretty good shape, but try the following to check your config out:
___- Change through all the channels
___- if you run across a channel with low signal strength (or one that is "signed off")
______- you will end up with a black screen and the system will appear hung you will be bumped back to the main MythTV menu
______- you will not be able to enter "Live TV" mode again
___- I haven't found an easier way to correct this and if you are going to be doing a lot on antenna "tuning", get used to this sequence (commands follow $ or #)
______- exit mythfrontend
______- open a shell
______- $ /etc/init.d/mythtv-backend stop
______- $ mythtv-setup
______- under 4 set the starting channel to a known good signal strength channel
______- exit mythtv-setup
______- $ su
______- # /etc/init.d/mythtv-backend start
______- # exit
______- $ mythfrontend
___- You should be able to view live TV again, but obviously you have a problem with low signal strength channel
___- Not being an antenna installation expert, I don't have a signal strength meter, but I needed a way to know if the changes in aiming the antenna were increasing or decreasing signal strength
___- The Air2PC card can be used to give you signal strength, there are several ways, but the following worked best for me
___- on a separate system (I used my laptop so I could be at the antenna and see real time feedback of changes I made, so the following is based on using an M$ os)
______- install PUTTY or something like it on your M$ machine
______- install VNC on the myth box and a VNC client on your M$ machine
______- See the wiki how to for more info: http://www.knoppmythwiki.org/index.php?page=HowTo
______- Connect to your myth box with PUTTY
_________- $ femon
_________- this will give you a running indication of the signal strength, signal to noise ratio as well as other info for the current channel the card is tuned to
_________- you want a signal strength of greater than 8000, but the closer to ffff the better
_________- use VNC to control mythfrontend, switch to live TV mode and change channels while you mess with the antenna (when in live TV mode you can't see anything on VNC, so make the window active and type in the channel number to change channels)
_________- if you have a lot of weak signals you will getting stuck quick a bit with a "black screen" and need to use the procedure I described above to reset the starting channel

- Once you have your antenna(s) set up and are getting ffff signal strength for all channels (good luck ), you need to get your guide to look pretty
- In my case none of the zap2it info matched exactly what the channel scan got out of the OTA channel data stream
___- exit mythfrontend
___- open a shell
___- $ /etc/init.d/mythtv-backend stop
___- $ mythtv-setup
___- Select 5
______- the zap2it channels are usually listed with an "_" and the OTA found channels are listed with no separator
______- I prefer no separator to make direct channel entry work with a remote
______- I modified my OTA found channels the "active" ones by doing the following:
_________- from a zap2it channel get the Callsign and XMLTV ID
_________- replace the callsign in the equivalent OTA found channel and add the XMLTV ID
_________- repeat for all channels (this is a pain, and there is probably a quick way to do this)
______- exit mythtv-setup
______- $ su
______- # /etc/init.d/mythtv-backend start
______- # exit
______- $ mythfilldatabase
______- $ mythfrontend

- you can clean up your guide by logging into the myth box with a web browser (see the wiki how to for setup instructions) and under "Edit MythWeb and...", click on channels, and on the far right uncheck "visible" for the zap2it channels to hide them, click save at the bottom of the page


I am sure there are easier ways to do many of the steps I described above, but this worked for me and I am (knock on wood) fast approaching a setup that will meet the WAF requirements.

Items I am still investigating:
- A better way to get "unstuck" from a channel that is "signed off". The local PBS station has 4 sub-channels and usually 2 of the 4 are signed off. When I accidentally change to a signed off sub channel, I have to follow my procedure described above to reset the starting channel. This one really hurts the WAF.
- Transcoding. There are a lot of threads on this, but I haven't been able to find a simple "how to" to follow. I want to automatically transcode and keep commercial flags (after recording, and commercial flagging) a full HDTV TS MPEG2 stream (1920x1080, 6GB/hour) into a lower res xvid which will look just fine on my set. I don't care about how long it takes to encode.

Anyway, hope the above helps someone else.

vtdstein95

Indeed this does help, if for no other reason than to confirm I'm not crazy! I've been tinkering with the exact same problems you wrote about for the last few weeks, but in my case without success. I was beginning to think that I had something configured wrong in the software, but I'm once again inspired to try and mess with the antenna again. (Besides, my eyes have glazed over from looking through all the log files!)

I'm going to try your suggestion about using the Air2PC as a "signal strength" indicator. I'll post my results.

For the record, vtdstein95's description of how to "fix" the DVB card after trying to view a bad channel (i.e. too low signal strength or signed off) is the same thing I've been doing. At one time I remember seeing a status message somewhere that referred to the DVB card as being "busy". I wish I could remember where I saw that... probably in a log file somwhere...

I actually have a PVR-150 and an Air2PC card. After viewing a bad channel with the Air2PC I can switch to the PVR-150 card (by hitting "Y") and continue to watch LiveTV. Everything else continues to operate just fine, but I have to use vtdstein95's restart sequence to attempt another Air2PC viewing.

Anyway, thanks for the writeup!

I've been waiting to try this until a few more guinea pigs are successful.
I think the time has come for me to jump in too.

Ditto on the transcode how-to if anyone is up to it.

I think my amd athalon XP2600 is probably not up to playing back HD on my computer monitor and my big screen is analog anyway. I would be happy just to have better looking "free tv" in standard defintion for now until processors and hdtv's get more affordable.

BTW, I think I have respectable analog tv-out over s-vhs with a matrox g400. Would I need the video card assistance of a geforce 4mx 5200 in order to have good playback of downsized HDTV over s-vhs? I'm a little confused here. Is it true that slower PC's could use the AIR2PC but only watch the shows after transcoding to a lower resolution?

I'm sure someone might say this is all too much trouble and stick with rabitt ears a pvr100 and an old matrox card.
Or if you're going with the air2pc at least make sure your computer is fast enough to watch it on the CRT monitor in all its beauty.

I have close to the same situation. In fact I'm going to hopefully experiment soon with some different hardware.
Here's my current specs:
Socket A M/B
Duron 700
Geforce3 Ti 200 64MB AGP
PVR-150 non-mce w/ remote
Air2PC r0.2 ATSC HDTV tuner
384MB RAM
160GB HDD

Recording and playback with just the PVR-150 is NO problem.
Recording with the Air2PC Card seems fine.
Playback of the digital content captured from the Air2PC card...forget it.

First test: I'm going to use my video card and both tuners in an Athlon XP 2800 box with 1GB DDR. I'm going to see if capture and playback will improve enough to not need a faster video card.

Second test: I'm going to use my MB, Pro, RAM and tuner cards along with a GeForce 6600GT AGP card to see if playback of digital content is better.

I will post results of my tests when I get them. Hope this helps someone.

(BTW, my main emphasis of this post should be that I have been VERY successful with the Air2PC R0.2 *eBay purchase* Quality seems great from what I can tell)

Update #1
After a successful installation of R5A30.1 onto my loaner Athlon XP 2800 w/ 1GB DDR proves to help, but not solve my issue.
Playback of digital SD channels seem smooth, however playback of HD channels still stutter intermittently.
I ran # top and noticed that consistently 'mythfrontend' was hovering around 75% and Xfree86 hovered around 25%. And without having to do much math, you can see it has maxed out my system.

I have read and understand the recommendation of at least a P4 2.4 for HD playback, but I'm still wondering if upgrading my video card will take any stress off of the processor. If anyone has any input, please let me know. I tried to use XVMC however my card apparantly doesn't support it because it states there is a problem with the playback device.

I will update when I get a hold of my loaner Geforce 6600GT.

Update #2
I got a hold of the loaner video card this morning: eVGA 6600GT 128 AGP
I installed the card into my Athlon XP 2800 box and after a second reboot, I was able to watch my pre-recorded shows with NO problems.

Playback of HD and SD content was flawless. (with the exception that my HD channels are vertically squished, but that's another story)

So with one test left to go (6600GT in the Duron 700 box) I have a couple of questions.
a) do I need a card like 6600GT (or 6200) with Hardware Decoding -or-
b) can I get away with a standard FX5200 card
c) if I get a lesser powerful video card, do I need a faster motherboard/processor combo -and-
d) vice-versa, if I get a more powerful video card, can I resort to less MB/Proc speeds

Update #3 (I hope this is helping others!)
Final Setup test
eVGA 6600GT 128MB AGP
AMD Duron 700
384MB SDRAM

As the video playback with the Duron 700 and Geforce Ti 200 was unwatchable, it was 'better' with the 6600GT.
I tried xvmc setting on and off
xvmc off:
-processor usage ~99% all the time
-video was fairly smooth on SD recordings
-video was jittery on HD recordings

xvmc on:
-processor usage ~45%-65%
-video was very good on SD recordings
-video was a bit jumpy on HD recordings but MUCH better than without XVMC

Now, as I've been reading, XVMC seems buggy to others and apparently has issues with the 6200. At this point I'm more apt to get a MB/Proc combo first and wait out the video card.

Wow, that's some significant difference with the Duron 700 when watching HD. I have a Sempron 3000+ and a GeForce 4200, but enabling XvMC only reduces my CPU usage from the same 75/25 frontend/xfree usage to 75% mythfrontend and no xfree cpu usage.

I gave up tweaking this because I was able to get full frame rate HD flawlessly, but it your data is correct then with my system tuned properly then I should be able to get by with 20% cpu usage or so...

I was just able to try an FX5500 (my new permanant card) along with the Duron 700.
With XVMC turned off my processor was peaked at 99% again, however with XVMC turned on, depending on the channel I watched, it lowered it to 75%-65%
I was still stuttering on the 1080 HD channels, but smooth on the lower res HD channels and all SD channels. A nice 3GHz processor should prove to finish my project.

I know a bunch of us trying to figure out how cheap we really can go when building the Myth box, so I help this has helped!

First post, GREAT forum, I have learned a lot here getting things tweaked!

I got a rev 0.2 Air2PC card a few weeks ago as well as using the DVB-Tools to manually test it, got it working and had same difficulties in playback with my system.

Athlon XP 2900 (2.0 GHZ) with Geforce4 MX 440.

Played back standard def. and 720p stuff fine, but could not handle 1080i without stuttering badly. The temp fix was downgrading my XF88Free-4 File to only use a 800x600 resolution.

Last week I found a couple of 128MB Geforce FX 5900SE's on clearance for $50 each (256MB memory bandwidth, roughly same raw speed as a 6600GT or 6800 without some newer bells and whistles on the GPU)

I can run my desktop resolution at 1280x1024 now and only use about 40% cpu usage on 1080i material with xvmc enabled using bob detinterlacing.

To test the Video card further, I changed my cpu bus speed so the process only ran at 1.0GHz (equivient to a XP 1400 or so?) and the cpu load went to about 65-75% during 1080i playback. Picture looked great and smooth.

A really fast video card makes a big difference. I plan to peice together another machine with my other video card to use as a 2nd front end.

I figure even with a slower system, one can downgrade the desktop resolution to take the load off the video card if need be if the video card is not fast enough.

Great post on signal strength monitoring. This worked perfectly within minutes to get the antenna going to my PCHDTV 3000 card in my Dragon Knoppmyth box.

I admit that all the putty and ssh jargon would have been greek to me some time ago.

Wanting to record the world series for free in HD off the air for bragging rights drove me to try to get the Dragon box running in time.

Seems you need a perfect signal to even start to get an atsc box running, Dragon or home built.
So I set everything up to get one channel only, WMTW with zap2it, and the WMTW starting channel on the box, and using putty on my laptop to be sure of a good signal.

Lucked out in planting my log-periodic "rabbit ears" in a good spot to start with so system would not crash, but as this poster mentioned, just get used to doing the code dance to recover quickly from a crash or lockup.

_________________
Mythic Dragon V1.0, R5F27
--
Stars Up, Lights Down...
Be a good neighbor, shield your lights, save electricity, and be more secure. Darksky.org

Thanks again for the how-to.

I followed the instructions but it seems to be taking forever at the scan step.
i am supposed to be in a very strong area for pbs so 4-1 through 4-4 should find a signal when it scans asctv channel 4 right... but it says could not tune timeout and never finds any channels up through the 20s so far. The antenna is a small thing with a plug in amp that came with it from ebay, but it seems like i could still pull in the pbs channel at least.

Any ideas? I will probably pick up an antennae from radio shack.

The numbers you see during the scan are not directly related to the DTV channel numbers. Each station is assigned a frequency in the UHF range to broadcast ATSC. The FCC wants the VHF range to auction off which is really the biggest reason for the push to ATSC. Channel 4-1 through 4-4 (all carried in the bandwidth of a single channel) could be on any single UHF frequncy (NTSC channels 12 on up). The channel numbers are now more symbolic and don't neccesarily represent the frequency range. In my area channel 5-1 is on UHF channel 59 (if I recall correctly).

Anyway, sorry for the rambling. The scan does take a while, but should be complete in less than 5min. If at the end you don't see a 4-1 and all the other 4-x sub channels, then try re-scanning. If other channels are found, but not it, then it is your antenna that needs work.

vtdstein95

Thanks. Channel 4-1 through 4-4 are supposed to be OTA broadcast on channel 59 for me and it is 9 miles away according to antenna web .org so I doubt the antenna is the issue. It was included as an indoor amplified hdtv antenna when i bought my rev 0.2 air2pc off ebay...

Anyway the scan takes well over an hour and finds nothing. The signal never changes from zero and it just slowly decides failed to tune for each channel.

My card is recognized in dmesg and in mythtv-setup so I don't know why it isn't finding anything.

Maybe i should try to send it back. I bought it for $80 in july. now the airstar hd5000 are only $120 maybe i should have been more patient.

My current troubleshooting ideas are
1) should i try different firmware... I used the firmware mentioned above but some how-tos mentioned dvb-fe-nxt2002.fw

2) are the header files incorrect as was this guys problem a while back... he wasn't using knoppmyth r5v30.2 though... http://www.avsforum.com/avs-vb/showthread.php?t=509869

I would agree this problem is not your antenna, channel scan takes minuets, not hours. Not to say you won't have an antenna problem when you get this problem fixed. Search for clues...

What do you seen in /var/log/myth/mythbackend.log? Although I don't recall if this is updated during mythtv-setup.

What does femon say, also you can run it while the scan is going on...may be a clue there.

Try the firmware.