[mythtv-users] CPU power for digital tuners
jcw at wilsonet.com
Sat Jul 10 05:34:36 EDT 2004
On Jul 9, 2004, at 23:39, Rudy Zijlstra wrote:
> Jarod Wilson wrote:
>> Typical US ATSC HDTV streams are usually 19.2 Mbps (though they can
>> be greater).
> Some comments:
> ATSC TS is either 19.2 or 38.4 Mbps.
Actually, I believe they can be quite a few different bandwidths. There
are 18 different HDTV "standards"... 19.4 (not 19.2, actually,
according to a few sites I googled) seems to be fairly standard for
1080i and 720p streams, but 480p streams definitely aren't using as
much bandwidth. (I have a pcHDTV card, btw).
> Terrestrial will always be 19.2.
No, not always.
> On the cable 38.4 is possible.
Its possible OTA as well. Depends on if you're talking per-sub-channel,
or the entire channel though, I think. And if you're grabbing all the
audio tracks, etc... And from my experience, the cable company
(Comcast, in my case) actually makes an effort to *reduce* the required
bandwidth per channel, breaking everything out into its own channel.
For example, PBS in my area broadcasts on a channel that carries four
sub-channels. I think 3 are 1080i, one is 480p, but all the same
channel. Its something like 60Mbps for the entire channel, which you
can capture in its entirety as a single mpeg2-ts (I believe). Comcast
puts each of those on a distinct channel, no way to get all of them at
> ATSC may be HD, but at the moment is mostly SD.
Huh? You mean SD 480i stuff up-sampled to 480p? Yes there's a fair
amount of that. Technically, that's still HD though, not SD... But most
of the stuff in my area is true HD (1080i or 720p). At least that's the
case in prime-time.
> ATSC simply has a table of supported HD formats, whereas DVB does not
> have that table.
I presume you're referring to this:
> DVB has MP at HL though...
> and is thus able to support anything that ATSC does.
Resolution-wise only, or does that include 8VSB (OTA) and QAM (cable)
encoding of the stream? For example, do you believe a DVB-T card could
tune in ATSC streams in the US? (I'm assuming not).
Jarod C. Wilson, RHCE
jcw at wilsonet.com
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