Trying to understand MPEG-2 TS -> HDMI inflation

[Golem]

In general -- I assume Comcast delivers content via an MPEG-2 TS which is in turn either converted by the STB to analog for the Composite/Component-out, left as untouched MPEG-2 TS for IEEE 1394-out or uncompressed for HDMI-out. The latter is where my curiosity really lies. I really don't understand how HDMI could provide superior image quality vs the original MPEG-2 TS since it is being inflated from a lossy compression. I could comprehend this if we were talking about a loss-less compression but this isn't so.

Any insight much appreciated.

[usually_quiet]

In general -- I assume Comcast delivers content via an MPEG-2 TS which is in turn either converted by the STB to analog for the Composite/Component-out, left as untouched MPEG-2 TS for IEEE 1394-out or uncompressed for HDMI-out. The latter is where my curiosity really lies. I really don't understand how HDMI could provide superior image quality vs the original MPEG-2 TS since it is being inflated from a lossy compression. I could comprehend this if we were talking about a loss-less compression but this isn't so.

Any insight much appreciated.

It isn't left untouched for HDMI output. It is decoded, decompressed, and possibly scaled. Cable boxes are often set up to scale video for HDMI output so that it always matches the nominal resolution for the HDTV, 1080i or 720p. If the TV processes MPEG-2 video, it must do the same kind of processing internally. However, most 720p TVs are 1366x768 resolution not 1280x720 so 720p HDMI input is usually scaled by the TV as well as by the cable box,

[newpball]

It isn't left untouched for HDMI output. It is decoded, decompressed, and possibly scaled. Cable boxes are often set up to scale video for HDMI output so that it always matches the nominal resolution for the HDTV, 1080i or 720p. If the TV processes MPEG-2 video, it must do the same kind of processing internally. However, most 720p TVs are 1366x768 resolution not 1280x720 so 720p HDMI input is usually scaled by the TV as well as by the cable box,

What a mess!

[usually_quiet]

It isn't as bad as it sounds. I only know that my cable box scales on account of fiddling with HDMI output settings to turn off scaling for recording TV shows using my Hauppauge Colossus.

That being said, assuming most of my preferred TV shows are copy freely, I'll have the opportunity to watch MPEG-2 processed only by my TV (via its media player) to see if I notice any difference. I bought a CableCARD tuner recently, although I still have to drive across town to get the CableCARD to go with it.

[Golem]

Thanks for the replies!

I guess what I'm really asking is -- Since MPEG-2 is a lossy compression and Comcast's TS averages 6 Gb/h how does the decompression to HDMI at +/-344 Gb/h improve on picture quality? Where I lose it is in the "understanding(?)" that information is discarded upon compression to MPEG-2 which can not be recovered during decompression to HDMI. I know I'm missing something here.

P.S. -- LOL, Just reread my OP question and seems I'm basically reiterating here. Be kind, my brain's a bit fried at the moment from trying to research this prior to posing the query.

[usually_quiet]

Yes, there is information lost when the original source video is compressed to MPEG-2 and there is no way to recover it. The purpose of HDMI is not to improve the MPEG-2 picture data or recover lost data, only to provide a secure path for an uncompressed digital video signal.

Cable companies originally decided to go with HDMI because it offered better copy protection and other technical advantages over Firewire. For example, with HDMI, your set top box is responsible for decompression, which means you don't have to get a new TV or a converter box as would be the case if there were no HDMI outputs on set top boxes, only Firewire, and your TV provider were to switch to H.264 compression for service.

[Golem]

The purpose of HDMI is not to improve the MPEG-2 picture data or recover lost data, only to provide a secure path for an uncompressed digital video signal.

Ah! That's exactly the info I was fishing for.

Much appreciate the enlightenment.