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HDTV in SDTV Mode - HDTV n00b questions.
PostPosted: Mon Jun 07, 2004 8:33 am Reply with quote
ScubaStreb
 
Joined: 07 Jun 2004
Posts: 2




Greetings!

I'm considering purchasing a HD-2000 card and building a MythTV system. However, before doing so, I have some noob questions.

First, I'm not much of an audio/video enthusiast. The extent of my enthusiasm goes as far as enjoying the quality of my DVDs and the previous good quality of my DirecTV system which I no longer subscribe to. DirecTV was fine for me, but I hated paying $40.00/month for the basic package with local channels and DirecTivo when all I wanted it for was local channels.

I don't really care about HD television, but want the digital clarity of satellite using over the air signals. I own a nice, relatively new, Toshiba flat screen television that is not HD ready though.

OK, enough background info and on to the questions:

- If I purchase the HD-2000, will it work on my non HD ready TV set? I assume that it will if I output it to a 480 mode, However, I just want final clarification before spending the $200.00.

- If I use MythTV to record liveTV, can I save the HD signals in a 480 mode without transcoding the streams, or do they have to be saved in HDTV format? I will be buying a ~200 MB hard drive, so it's not a huge deal if that is the only way to initially save them, but I would rather do it in a smaller size then the HDTV size. I'll be running an Athlon2600 and using a Geforce 5200 video card, but I don't want to risk poor playback by constantly taxing the cpu by transcoding.

Thanks in advance to any help on this matter. I've been running GNU/Linux as my primary machine for years now, and this looks like a fun project.

Cheers!
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PostPosted: Mon Jun 07, 2004 11:40 am Reply with quote
mk500
 
Joined: 11 Jan 2004
Posts: 51
Location: San Francisco, CA




I'm in a similar situation to you. I got into Over The Air (OTA) HDTV/DTV because I love having "DVD quality" TV without the high monthly bills. My TV is a Sony WEGA that is about 5 years old, so it doesn't support anything beyond DVD quality. I'll answer your questions, and then give you some pointers to get you started more quickly:

1) down-sampling (going from 1080i or 720p HDTV to 480i for your TV)

The HD2000 card basically will write an MPEG2 ".ts" file to your hard drive. It will not do on-the-fly down-sampling like a set-top box. It actually doesn't change the data at all, which is one of the things that's cool about it for enthusiasts. You get the raw stream right off the air. You might want to consider something like the RCA DTC-100 if you want something simple to do down-sampling right to the TV (I had been using one of these for years before buying the HD2000 card, and it's great)

2) size of files

Since the whole stream is going to disk, the files can be quite large. Up to 9gigs for 1 hour of video. It's important to note that several "sub-channels" might be a part of that one ".ts" stream file. My local PBS station in San Francisco broadcasts one HDTV signal and 4 more DTV signals all in the one stream. In order to reduce size and ONLY record the "sub-channel" you want, I recommend the excellent command line tool "dtvstream" by pdicamillo. Here is the link:

http://www.pchdtv.com/forum/viewtopic.php?t=157&highlight=dtvstream

For me, this is the only tool I have gotten 100% reliable recording with.

3) distro/hardware advice

If you have a machine to dedicate to your new hobby, I recommend it. To start off with, you can use a pretty slow machine to experiment with recording, then transfer the file to some other box to watch on (VLC is a great tool to watch on any kind of OS; mplayer or xine-hd on linux). Once you are an expert, you'll be more prepared to build an optimized home theater PC around your card. Save yourself HUGE amounts of time by just downloading the newest KnoppMyth and letting it automatically build a fully opperational Debian install on your disk for you. This is a great starting off point, and will probably save you 10-100 hours of work. You just burn this ISO, boot off it, and choose auto-install. This will re-format and partition your hard drive, then install a fully functional Myth/Debian system:

http://mysettopbox.tv/knoppmyth.html

Just download it from one of the mirrors listed on the homepage. Once you've gone through auto-install, you need to change out the kernel to support pcHDTV. This is super simple:

Code:
as root:
     cd /usr/src/debs/pchdtv_kernel/
     dpkg --force-overwrite -i kernel-*.deb
     answer Yes to everything
     reboot


With those simple steps, you should now be able to run all the pcHDTV command line tools. The first one you'll want to try is signal. Copy the tools directory from your CD to somewhere on your new Myth system.

./signal /dev/dtv 45

Where "45" is a local digital broadcast station number. You should have a signal over 80. If not, you may want to work on your antenna. Ctrl-c to stop showing the signal. Next I would recommend you try recording a show with dtvstream, then go watch it on your computer. You'll start to understand the processor and video card needs of a HD stream pretty fast this way Smile

4) MythTV

If you followed my advice above, you have a fully working Myth system. You'll need to setup your pcHDTV card by going through the GUI setup application in /usr/local/bin/mythtv-setup. There is a great set of instructions for doing the setup here:

http://www.pchdtv.com/forum/viewtopic.php?t=12

You can skip down to the "Once you have built atleast mythtv and installed" paragraph. One word of caution:

I have never been able to fully get Myth to be able to record streams for me with stability. With much work, I was able to at least flip through my channels and watch TV, but I always run into problems with the mythbackend crashing when trying to record. Hopefully you will have better luck. Other folks here and on the KnoppMyth forums probably can better help you with MythTV

5) "not much of an audio/video enthusiast" & " this looks like a fun project"

It is a fun project. But for me, and I believe others here, it's become more of a hobby. You can put a LOT of hours into getting what you want out of this system. It is NOT anywhere near a "commercial" package....it's hobbyist all the way. I think I've probably put about $1200 and maybe 200 hours into my systems. I have two pcHDTV enabled boxes. One slow one for tinkering, and one "production" one in the living room for watching on (that way I don't infuriate the wife my constantly rebuilding the main box).

Good luck, and welcome!
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PostPosted: Mon Jun 07, 2004 11:47 am Reply with quote
mk500
 
Joined: 11 Jan 2004
Posts: 51
Location: San Francisco, CA




One more thing I forgot to mention:

You can transcode the .ts file to a lower resolution file for watching/storing after the fact. Maybe with a fast enough machine you could do this in real time? (maybe dual 3Ghz box?)

One of my boxes is an M AthlonXP 2600 with a nVidia 5200 also. I'm experimenting with "transcode" now, and will post when I have a good working example, as others have been asking about this.

Someone else posted that they are using "mplayer" to transcode as well, but I haven't tried this.
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PostPosted: Mon Jun 07, 2004 2:47 pm Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




I've never had any luck with transcode. It's always bombed as soon as it hits a transport error. I must be doing something wrong but I didn't bother to figure it out. mencoder works fine for me.
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PostPosted: Tue Jun 08, 2004 8:28 am Reply with quote
ScubaStreb
 
Joined: 07 Jun 2004
Posts: 2




MK500, thank you very much for the reply! I think this is the route to go afterall. Part of the reason that I'm interested in this is for the PVR functionality as well playing my music files. However, I will be using the box that this will be running on to make backup copies of my DVDs, burn DVDs and hopefully, shrink the saved files of my favorite series and burn them to DVDs.

I was looking at the KnopMyth site the other day and it looks like a very nice distro. I may give it a shot. However, I run Gentoo on everything else and will probably go that direction since I'm more comfortable in Gentoo than Debian. Since I'll be doing more than just the MythTV functions, it might make my life easier after initial setup.

Scott, I have had very good luck using Transcode on regular DVD9s to back them up to DVD5s. I know this isn't exactly the same thing, but hopefully I can get it running.

Cheers!
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PostPosted: Tue Jun 08, 2004 1:55 pm Reply with quote
Scott Larson
 
Joined: 15 Oct 2003
Posts: 713
Location: Portland, OR




If anyone has a transcode command line that turns a saved transport stream into something else, maybe I can figure out what I'm doing wrong.
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PostPosted: Wed Jun 09, 2004 12:14 am Reply with quote
mk500
 
Joined: 11 Jan 2004
Posts: 51
Location: San Francisco, CA




Scott Larson wrote:
If anyone has a transcode command line that turns a saved transport stream into something else, maybe I can figure out what I'm doing wrong.


This is as far as I've gotten. It worked, but no sound. I feel I'm close Smile

Code:
transcode -i Summerland_Pilot.ts --ts_pid 0x11 -x mpeg2,null -g 1920x1088 -H 0 -V -Z 400x300 -y mpeg2enc,null -o newmovie.mpg


ver transcode v0.6.4.20030409
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