I recently decided to make an addition to my NTSC MythTV setups by putting a Dvico FusionHDTV5 Lite in what used to be a front end only box. The system plays the HDTV streams beautifully, but man does it eat up some disk space and I/O! The question I have is whether or not anyone has managed to downsample, or even scale down, the MPEG-2 streams on the fly? I have a 42" plasma EDTV for now, but even when I upgrade to a new HDTV monitor later this year, I don't want to have to put a 300GB drive in this machine just to have enough space for a few days worth of shows. I was thinking of scaling down the stream to 852x480 (EDTV res) *or* maybe changing the sample rate so that it ate up less disk. Anybody tried this?

Scott

Keep in mind the HDTV cards like the HD3000 or the Dvico are not encoding anything... they're simply taking the data stream that's coming over the air or over cable and dumping it to disk. So you don't really have any options for changing the sampling rate. (I'm surprised that your I/O is being eaten up while recording. Playback, maybe, but recording is supposed to be very low-impact.)

I'd be surprised if anything could resample/transcode on the fly.

Just buy the disks, Scott. I've looked into it a bit, and everyone so far tells me it's impossible to transcode HDTV down to lower resolution efficiently. You can DO it, but it takes longer than the running time of the show. In other words, it takes several hours to transcode a one-hour program. Not good.

I know only enough about MPEG encoding to be dangerous, but it seemed to me you could do something more efficient to reduce the size of the image, especially if you were willing to live with integer multipliers for numerator and denomerator. But I am told by those who know more than I that it won't work.

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The I/O issues that I'm seeing aren't from the recording, but from watching Live TV along with playback. If you're just watching along in "real time" there are no issues, but if you jump ahead or back you have a second or two of staggered video & audio until it catches up.

I understand about the cards not encoding - that's the beauty of digital tv. I was just wondering if there was so much redundancy in the codec that you could drop maybe every 3rd frame and still have a gorgeous looking image. Scaling, I imagine, would need to be written to use some of the video card algorithms rather than using the CPU.

Now if Comcast would just hurry up and start simulcasting all of the analog channels in digital, I'd be set. Well, that and leave the PSIDs in the stream instead of stripping them all out.

Scott

does this mean you are using QAM to record directly from the coax? if so could you write up a howto? I gave up on that a while back because mythtv wouldn't even scan for the channels, though that has been quite some time ago. now I use firewire, however If I could get QAM going I would have two hd and two sd tuners I could have going all at the same time would be great.

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Xsecrets

What modeline are you using (and what video card)?

I'm using an MSI MEGA 180 with an Athlon 2600+ CPU and 1 GB of RAM. I've got the modeline set to standard 1280x1024 (overkill for the tv, but it still looks great) and a DisplaySize 480 270 to correct the aspect ratio.

And to answer Xsecrets - I've got Comcast tuning working in Xine/MPlayer, but not MythTV. The PSID being stripped is a major source of grumbling for me just as much as it is for you. If I can figure out the channel info in MythTV I'll post a how-to on getting Comcast channels to work.

Scott

I think you would do better with an 848x480 modeline...I use one for my EDTV projector and it works/looks great.