[mythtv-users] OTA/DTV tuner-card related questions, recommendations

[James Miller]

Thanks for your response.

> You have a horrible misconception of OTA digital TV.

Hmmm. I thought my disclaimer about having modest technical abilities 
might have prepared readers for that possibility. Are you surprised? I 
often stand in amazement at myself for ever having been able to set up and 
administer my mythtv box. And I'm sure there are many, many more myth 
users out there with comparably horrible misconceptions of various kinds. 
But, anyway, on to your points.

> The simplest thing for a tuner to do is to stream the already compressed 
> HDTV digital signal directly to the hard disk. The signal is already HD. 
> To get an SD signal as you imply you want, one must first decompress the 
> HD signal, re-scale it to SD, then decompress before saving to disk. 
> This is extremely processor intensive, and an older PC would be 
> incapable of doing this in real time.
>
> If you really want an SD signal, you should save the HD signal to disk 
> in real time, and once it is recorded, trans-code it (over night on your 
> slow system) to SD.

Interesting explanation. And there's a lesson to be learned here as well: 
never hesitate to display your ignorance--you could end up learning some 
things that, had you feigned greater knowledge, you may well not have. I 
do have a larger disk I've been planning to put in for some time (500GB), 
so it's evident that will be a prerequisite.

As far as wanting an SD signal, I don't care either way. I think I could 
watch either and get the desired effect. The 800x600 resolution my monitor 
displays looks more than adequate to me, in all honesty. But I'm not sure 
I could watch an HD broadcast on that monitor, even if I wanted to, could 
I? So converting to SD may not be a matter of wanting this or that, but a 
question of necessity.

To summarize, OTA DTV is HD by definition. If you don't have hardware 
capable of displaying HD and want to watch/record OTA DTV using mythtv, 
you'll need to transcode the broadcast--which, if done in real time, is 
likely to turn your old hardware into a mass of molten metal and plastic. 
If done subsequent to recording the broadcast, the transcoding will work, 
but you're liable to perish of old age before the job completes. And all 
this in the name of progress!

Anyway, I'm learning--a good part of what I'm after.

> HDHomeRun is a reliable & simple to use ATSC/QAM tuner that works well 
> with MythTV. There are many USB tuners, PCI tuners, and
> even PCI Express tuners available for cheaper.

I don't have a PCIExpress slot in this machine. It's gotta be PCI or USB. 
And brand names and model numbers would be most helpful: I presume there 
are all kinds of bargains to be had, but not every capture device that is 
as inexpensive as I'd like is necessarily going to work with myth, right?

Let me ask this in closing. As I understand it, my PVR150 does some 
processing of the signal before dumping it to the hard drive, correct? I 
realize HD enthusiasts would consider it sacrilege, and that hardware 
manufacturers would rather have their toenails pulled out by the roots 
than to even think of designing something that would do this, but I gotta 
ask anyway: is there some HD tuner card that can help my old P4 reduce the 
HD to SD in something like the way the PVR150 (if I've understood 
correctly how it works) processes the signal before dumping it to the hard 
disk?

Thanks,
James