Log in Register FAQ Memberlist Search pcHDTV Forum Index
pcHDTV Forum

pcHDTV Forum Index -> General pcHDTV topics -> So far HD300 is interesting, but I have far to go...
Post new topic  This topic is locked: you cannot edit posts or make replies. View previous topic :: View next topic 
So far HD300 is interesting, but I have far to go...
PostPosted: Tue Jan 04, 2005 8:07 pm Reply with quote
dabbler
 
Joined: 04 Jan 2005
Posts: 24




I got the HD3000 for Christmas and have been fumbling around learning a few things from "well Duh!" to "I had no idea!" along with quirks and gotchas.

My base system is Fedora Core 2
3GHz Intel on an Intel 915PGN board
Cheapy PCI sound card because Fedora doesn't yet handle this motherboard sound chipset
1 GB of memory
eVGA nvidia 6800 128 PCIexpress video card

I have a small outside antenna but it doesn't have a very large UHF section. Neverthesless I get more HDTV signal than I expected.

I went after standard TV first as an easier target.

SOUND
After neither TVtime nor xawtv gave me any sound, I finally realized I had to use an external audio cable to jumper the HD3000 audio out to soundcard line-in to get sound.

Strangely sometimes the sound goes to pure static when switching channels. Switching back and forth sometimes restores the sound and sometimes doesn't. Sometimes mute/unmute works, but closing and restarting xawtv usually restores the sound in one cycle. I've notice this more with xawtv than TVtime.

Another sound quirk I've encountered twice now on both TVtime and xawtv is the sound is very tinny with a slight echo. Again a couple of restarts cured the problem.

VIDEO
I found that I had to reset the default mid-range "HUE" value all the way to the extreme to get normal colors.

Xine-HDTV
I get a one pixel line of flickering data at the top of most of the HD channels. Not a big deal but I find it annoying.

Changing channels between different resolutions often causes a video tear in the lower right portion of the image that requires stopping and restarting Xine-HDTV.

I find that I usually have to pause the video for a moment after starting to eliminate frame dropping. After a brief pause, the video becomes solid again.

RESOLUTION & CPU LOAD
Low res, (704 x 480), runs about 12% cpu
HD res, (1280 x 740), runs about 50% cpu

Whoa! I didn't even know this resolution existed??
Super res, (1920 x 1080). CPU pegs at 100% and drops frames like mad.

I recorded a brief clip of super res with getatsc /dev/dtv 27 > test27.ts
Just recording took my CPU load to 96%. However playing back the recorded stream with Mplayer was rock solid. The resolution is impressive. Unfortunately my screen won't go that high. Are there HD TVs that handle this super format? I'd never even heard of it!
View user's profile Send private message
PostPosted: Tue Jan 04, 2005 10:18 pm Reply with quote
k7ar
 
Joined: 14 Nov 2004
Posts: 12




Here are some misc comments:

AUDIO: You only need to provide a jumper cable for the analog NTSC channels. For digital/HD the audio is recorded as part of the digital data stream. It is played back through the /dev/pcm device.

VIDEO/HUE: Yes with the TVtime app, you have to turn the hue all the way to 0. Kind of strange.

Xine-HD: The flickering data you see at the top is data sent in the vertical interval. You can get around it by increasing the overscan a percent or two. I know how to do this in Myth but not in Xine. With an overscan of 0, you would see any data the station is sending. And I also have to hit Pause for a couple seconds then Play to get a solid picture in Xine.

Resolution: The 1920x1080 is 1080i HD, and there are two new LCD monitors from Sharp and Samsung that will display natively at this size. They sure look good in the stores but the price is around $8K. Most other TVs to the 1280x740 size.

Hope this helps, sounds like your new PC is very nice.

Good luck,
Al Rovner
View user's profile Send private message
PostPosted: Wed Jan 05, 2005 5:09 am Reply with quote
iwantmyhdtv
 
Joined: 05 Jan 2005
Posts: 12




On my setup, recording ATSC takes less than 1% of my CPU. Something must wrong, because it isn't doing any encoding work at all, it's just recording bytes that come straight from the card.

ALL Televisions that support HDTV should be able to handle a 1080i signal, as long as it is interlaced, because that's one of the two standard resolutions in North America. The other one you observed is called 720p, and its also a standard resolution. ABC tends to use that res, most of the other major networks use 1080i.

Xine has a zoom command, mapped by default to the "z" key, that can fix your overscan problem.
View user's profile Send private message
PostPosted: Wed Jan 05, 2005 7:18 pm Reply with quote
dabbler
 
Joined: 04 Jan 2005
Posts: 24




Thanks for the replies.

Regarding the high CPU load on a straight record. You're right, I don't yet know why but sometimes playing with Xine-HDTV it seems to leave things in a weird state, but I haven't been able to identify the pattern. Testing again shows that most of the time CPU on record is a trivial 1-2 percent.

Thanks for the education on 1080i being 1920 X 1080 interlaced, I didn't know that.

Perhaps you could explainn something else?

When I do a getatsc /dev/dtv 27 > myrecording.ts
I select the channel, (27), by looking up the Xine-HDTV channel indicator (26.1) on the antenna chart from www.antennaweb.com and finding the actual channel (27).

Now here's my question. Sometimes, but not always, there is a subchannel (26.2). This subchannel is not on the antennaweb listing. When I record channel 27, I assume that this is all subchannels. But when I play back with Mplayer, (via gui file play), Sometimes I get 26.1 and sometimes I get 26.2 . For another channel, I get video from one subchannel and audio from another. How do I control this in Mplayer?
View user's profile Send private message
program #'s
PostPosted: Wed Jan 05, 2005 9:29 pm Reply with quote
inkling
 
Joined: 05 Feb 2004
Posts: 342




dabbler wrote:

Now here's my question. Sometimes, but not always, there is a subchannel (26.2). This subchannel is not on the antennaweb listing. When I record channel 27, I assume that this is all subchannels. But when I play back with Mplayer, (via gui file play), Sometimes I get 26.1 and sometimes I get 26.2 . For another channel, I get video from one subchannel and audio from another. How do I control this in Mplayer?


xine -C x.1 x.ts
xine -C x.2 x.ts
xine -C x.3 x.ts

x doesn't matter if it's a pre-recorded stream, but it will use it to set the channel if you're trying xine direct playback.

Not sure what mplayer has in way of options to force the program number to play, but other people here might know.

I noticed the regular xine release has the same problem you're experiencing with mplayer, but xine-hd gives you the override against automatic stream detection.

Stations here are changing the program numbers as recently as last month, so antennaweb and others can get out of date fairly rapidly. Even zap2it doesn't list all the program channels on HDTV in my major metropolitan area.

It costs money for data entry people to type it in, eh? Same problem that's holding back universal PSIP data, I'll wager.

-ink
View user's profile Send private message
ATSC standards
PostPosted: Wed Jan 05, 2005 9:49 pm Reply with quote
inkling
 
Joined: 05 Feb 2004
Posts: 342




iwantmyhdtv wrote:
On my setup, recording ATSC takes less than 1% of my CPU. Something must wrong, because it isn't doing any encoding work at all, it's just recording bytes that come straight from the card.

ALL Televisions that support HDTV should be able to handle a 1080i signal, as long as it is interlaced, because that's one of the two standard resolutions in North America. The other one you observed is called 720p, and its also a standard resolution. ABC tends to use that res, most of the other major networks use 1080i.

Xine has a zoom command, mapped by default to the "z" key, that can fix your overscan problem.


You'd have a pretty old system if it needed more than 1% CPU to handle a 2.5 megabyte per second ATSC stream from the PCI card to the hard drive. DMA doesn't use much.

So nothing wrong there, as there is no encoding going on, only demodulating of the ATSC signal to an MPEGv2 Transport Stream and sending it over the PCI bus. It really is that simple. Think of as a 20 megabit receive only wireless modem.

I think there are 19 'standard' resolutions for DTV over ATSC. Most of them, fortunately, aren't used, but all are required to be supported for full compliance with standard.

For us, that's a player issue. The card doesn't care, it just moves bits from the air to the PCI bus. What you do with them is up to you.

FOX and ABC use 720p here. Rest use 1080i and mix of either 480p or 480i for the extra program streams.

I use the monitor zoom button to do the same as 'z' key, but I'll give the 'z' key a go.

-ink
View user's profile Send private message
So far HD300 is interesting, but I have far to go...
  pcHDTV Forum Index -> General pcHDTV topics
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
All times are GMT - 7 Hours  
Page 1 of 1  

  
  
 Post new topic  This topic is locked: you cannot edit posts or make replies.  


Powered by phpBB © 2001-2003 phpBB Group
Theme created by Vjacheslav Trushkin