[TiVo HD] Compression artifacts during Olympics - TiVo or cable?

[Teggy]

I just hooked up a refurb TiVo HD this weekend with an M-Card from RCN. Watching the Olympics (and other programming) I have noticed a lot of compression artifacts during certain scenes, such fast moving special effects shots or explosions. It is my understanding that TiVo does nothing to the HD signal, so does this imply that RCN is doing some significant compression on NBC and other channels?

[Videodrome]

It has to do with NBC compressing alot of data into there broadcast channel. First NBC has to convert it to US-HD. Then it has to put it on a carrier with 2 other channels. There has been alot of discussion of this on blogs.

[TonyD79]

There has been a lot of discussion (including much on avsforum).

What I have seen:

NBC via my OTA (WBAL Baltimore) looks great until you get to real fast motion such as men's diving. Then it breaks down.

UHD and the other channels are very good to excellent. Less breakdown.

The flying logo is always breaking down. Very much doubt it is HD.

The On Demand replay of the same stuff that was on NBC's main network via DirecTV (that is all I have access to) is much better in terms of fast action. While things like men's diving still breaks up, you can at least tell it is a man who is diving rather than a flesh-colored blob.

Once again, NBC shows up the worst on their flagship, the main NBC network, while does a creditable job with its other mechanisms.

[rainwater]

Once again, NBC shows up the worst on their flagship, the main NBC network, while does a creditable job with its other mechanisms.

Does your local NBC have sub channels?

[JJ]

Getting
similar results to TonyD79. Tested TiVoHD and Vista Media Center using both sources. Media Centers video processing seems to smooth the artifacts slightly better but mostly is a wash.

Cable artifacts are greater than OTA (possibly greater or recompression of signal) but artifacts clearly exist in both signals. Since these artifacts don't seem to exist in the slow motion replays I'm inclined to blame the MPEG compression and not the broadcast or receiving hardware. Locally our NBC affiliate WXIA-DT has no subchannels and signal glitches from the OTA broadcast are repeated in the cable signal. Somewhere between the pristine camera work and our homes artifacts appear. It will be interesting to see if he same artifacts are present in a BluRay version if one is forthcoming.

How did we ever watch these 'fast' sports in SDTV...

[DaveSt]

The local NBC affiliate's HD has *always* been inferior here (KMTR). It's pathetic sometimes, almost unwatchable. Makes no difference if it's viewed over cable or OTA. Oddly, sometimes the HD commercials look much better than the actual HD shows. I don't know if the "issue" is in the network feed, or if it's being mangled locally.

The TiVo is probably just showing you exactly how bad it is.

[tootal2]

I just hooked up a refurb TiVo HD this weekend with an M-Card from RCN. Watching the Olympics (and other programming) I have noticed a lot of compression artifacts during certain scenes, such fast moving special effects shots or explosions. It is my understanding that TiVo does nothing to the HD signal, so does this imply that RCN is doing some significant compression on NBC and other channels?

Im recording the Olympics on my tivo hd with a antenna. Looks good to me.

[flaminio99]

I'm new to Tivo HD and OTA HD and I have an SD set. During the first week, I watched the Olympics with a OTA digital tuner and it seemed perfect. Since I got the Tivo HD, I'm seeing the fast-motion artifacts as described. I could be mistaken, but it seems the Tivo is doing something. It's only been a mild annoyance cause the picture is enormously superior to my S2 and digital cable. My NBC has 2 subchannels (network and weather), however that affects things.

[aus1ander]

Also don't forget NBC uses 1080i; interlacing makes fast motion more prone to blurring and other artifacts compared to 720p.

[Y2Bogus]

I don't think the Tivo can be blamed for artifacting because from what I understand, Tivo doesn't perform any operation on digital channels. It copies bit for bit the digital signal that comes into it from your source.

That's why you don't get a quality option when recording digital sources, unlike the analog which has to be converted to digital by the Tivo.

[flaminio99]

http://www.tivocommunity.com/tivo-vb/showthread.php?t=369000

That thread there seems to show Tivo records whatever it gets. I don't think everyone is using a universal format, however, so don't know if there's some kind of Tivo transcoding going on.

I guess the only way for me to verify this is to watch live TV w/ a tuner and then compare to Tivo HD. Not sure I care that much since there's nothing I could do about it. :)