Capturing options for upscaled content?

[Golem]

When attempting to capture via Colossus internal what is clearly upscaled SD content on an 1080i HD channel would it be advantageous (picture quality wise) to set the cable box to output 720p (minimum resolution option)? If a channel is served at 1080i does this mean the original SD content is upscaled at the point of leaving the network or is it somehow sent out at SD resolutions then upscaled at the set-top box? If the former I'd assume only a small perceived improvement could come from simply downscaling to 720p at the box while, if the latter, I'd think skipping a 1080i upscale operation at the box would provide improved results at 720p.

This all has me wondering something else -- For stations that are offered with both SD and HD channel options by the cable company, are they provided two different streams from the networks?

Any info and suggestions to attain best quality would be appreciated as I seem to be zoning on this subject.

[KarMa]

Are all your channels 1080i? As all FOX stations and ABC stations broadcast 720p@60fps. So if you are getting 1080i for those stations, then upscaling is happening somewhere.

This all has me wondering something else -- For stations that are offered with both SD and HD channel options by the cable company, are they provided two different streams from the networks?

They are re-encoding every stream sent to your box, so it will fit within their bandwidth constraints and to be compatible with the decoder box in your house. So they are taking the feed for each channel and making a SD and a HD version.

And I don't think downscaling to 720p will improve anything, if it's a 1080i broadcast, as it just and another step for quality to be lost. Might reduce file size however.

[Golem]

Are all your channels 1080i? As all FOX stations and ABC stations broadcast 720p@60fps. So if you are getting 1080i, then something is off.

This all has me wondering something else -- For stations that are offered with both SD and HD channel options by the cable company, are they provided two different streams from the networks?

They are re-encoding every stream sent to your box, so it will fit within their bandwidth constraints and to be compatible with the decoder box in your house. So they are taking the feed for each channel and making a SD and a HD version.

Appreciate the reply.

Sadly I recently upgraded to the latest and greatest X1 platform and they really dumbed it down in an attempt to make it idiot-proof. The box can only be set to a fixed output resolution and, at that, only 1080i or 720p. I have to manually change between resolutions which means I sometimes forget and needlessly upscale 720p content thus reducing cap quality.

Your last sentence makes me pine for the good ol' days of Firewire recording where I was able to cap native resolution TS streams, 480i - 1080i. Grrrrrrrrrrrrrrrrrrr!

[usually_quiet]

Appreciate the reply.

Sadly I recently upgraded to the latest and greatest X1 platform and they really dumbed it down in an attempt to make it idiot-proof. The box can only be set to a fixed output resolution and, at that, only 1080i or 720p. I have to manually change between resolutions which means I sometimes forget and needlessly upscale 720p content thus reducing cap quality.

Your last sentence makes me pine for the good ol' days of Firewire recording where I was able to cap native resolution TS streams, 480i - 1080i. Grrrrrrrrrrrrrrrrrrr!

I understand. That is one reason why I now use a CableCARD tuner. Now, I don't have to fiddle with the cable box's output settings to ensure that every channel I record is captured in its broadcast resolution.

However, if you are a Comcast customer, you have either received a letter or will soon, notifying you that most HD channels will switch from MPEG-2 to H.264. What they don't explain in the letter is that channels which are currently 1080i will become 720p after the switch because 720p can be compressed more and is better for streaming. Most people won't know the difference. Many of Comcast's boxes output 720p only or are set to 720p by default.

The conversion started here last month and is taking place gradually. So far, 4-5 channels in my subscription have been switched.

[Golem]

Thanks usually_quiet. You are always a bearer of (ahem) happy news.

Guess I'm going to have to think on this bit of info and research the ramifications. I'll be wondering the following:

1. Since the X1 box currently outputs fixed resolution will the H.264 and 720p switch-over come with a firmware change allowing for auto-switching output resolution or will it blindly upscale in the interim. I'll have to keep an eye on the TVs switching snipe.

2. Might this make possible some sort of Colossus capture without the need for hardware transcoding? Maybe a looming Hauppauge provided firmware/software update?

3. Will this defunct the older Moto Firewire capable cable box I retained (not attached to my capture computer but used when I have special ClearQAM recording to do.)?

I thought I read somewhere that even CableCARD has a tenuous future?

[usually_quiet]

1. Since the X1 box currently outputs fixed resolution will the H.264 and 720p switch-over come with a firmware change allowing for auto-switching output resolution or will it blindly upscale in the interim. I'll have to keep an eye on the TVs switching snipe.

The reports I have seen indicate that there won't be any changes to what the X1 system does. It will continue to scale to the output resolution you set: 720p, 1080i, or 1080p.

2. Might this make possible some sort of Colossus capture without the need for hardware transcoding? Maybe a looming Hauppauge provided firmware/software update?

No. HDMI is uncompressed digital video, not a compressed digital video stream. There is no way to capture the original compressed stream without some kind of tuner.

3. Will this defunct the older Moto Firewire capable cable box I retained (not attached to my capture computer but used when I have special ClearQAM recording to do.)?

Probably. I know the old "DCT" and "DCH" boxes can't decode H.264, and will need to be replaced. The "DCX" boxes, "RNG" boxes and the HD DTAs are fine. CableCARD users are safe, if they have an HTPC or a recent TiVo model that can decode H.264. CableCARD TVs and older TiVos won't work anymore with the new H.264 channels because they can only decode MPEG-2.

SD-only cable boxes won't be affected because SD channels will remain MPEG-2.

I thought I read somewhere that even CableCARD has a tenuous future?

CableCARD probably won't go away until Comcast converts to an all-IPTV system. That is some years away. For now, cable operators are still required to provide CableCARDs on request and support them in third-party devices. Most of Comcast's cable boxes still use a CableCARD too.

[Brad]

This all has me wondering something else -- For stations that are offered with both SD and HD channel options by the cable company, are they provided two different streams from the networks?

They are re-encoding every stream sent to your box, so it will fit within their bandwidth constraints and to be compatible with the decoder box in your house. So they are taking the feed for each channel and making a SD and a HD version.

Correction: they are (usually, if not always) taking the separate HD & SD feeds provided by the broadcaster and possibly recompressing them, depending on the cable provider.

I don't know whether the new Discovery Family channel does this same nonsense, but here's an obvious example from its previous incarnation The Hub to show how the two feeds differ.



HD = vertically cropped 14:9; fewer compression artifacts thanks to higher bitrate; poorly deinterlaced (jaggies)
SD = 4:3; many compression artifacts due to low bitrate (the duplicated lines here were caused by the media player of the person who took the screenshot; the feed itself had no such issue)

The "Hub" logo bug covers a different portion of the woman's jacket and is pixel-perfect on the HD feed, so the upscaled image could not have been produced by the cable provider from the SD feed. And the SD feed could not have been produced from the HD feed, obviously, unless someone invented a magic "fill in top & bottom" filter.

[Golem]

Thanks for the reply usually_quiet!

No. HDMI is uncompressed digital video, not a compressed digital video stream. There is no way to capture the original compressed stream without some kind of tuner.

Argh, I had another Goober moment - Floating around my mind was transport stream not inflated HDMI. If I recall correctly you schooled me on that quite some time ago.

Probably. I know the old "DCT" and "DCH" boxes can't decode H.264, and will need to be replaced. The "DCX" boxes, "RNG" boxes and the HD DTAs are fine. CableCARD users are safe, if they have an HTPC or a recent TiVo model that can decode H.264. CableCARD TVs and older TiVos won't work anymore with the new H.264 channels because they can only decode MPEG-2.

That's promising news. The Firewire capable box I held on to is an RNG150N.

[Golem]

Appreciate the insight vaporeon800!

HD = vertically cropped 14:9; fewer compression artifacts thanks to higher bitrate; poorly deinterlaced (jaggies)
SD = 4:3; many compression artifacts due to low bitrate

That info provides even one more reason to decide which to capture (HDMI via Colossus or TS via Firewire). While I think it always best to capture in native resolution (when possible) the convenience of the always installed and ready Colossus ofttimes has me capping the upscaled content. Much prefer 4x3 (480i) over 14x9 (1080i) and not having to wonder what may have been cropped but have to wonder, based on your included images, whether even the 480i content is being compromised by way of bitrate neutering.

I guess the best way for me to test the "which is better", 1080i or 720p, when capping upscaled 4x3 content via HDMI (or Firewire to lesser extent) would be to find this scenario on VOD and perform both resolution recordings to do a pixel compare. As a casual (but prolific) capper I always hope there is either a definitive answer or, maybe, some tech-o-phile like you guys on this forum have already completed the tedious comparatives.

[Golem]

Just completed a quick and simple visual test. I captured the same upsampled video segment twice using Colossus with the only changes being the X1 box output set once for 720p and the other 1080i. Scrolling through the clips with VideoReDo both possess frames that look to indicate interlacing while only the 1080i clip properties denotes such. Not sure how it works but can I suspect it's not true 720p as the actual incoming stream from Comcast is 1080i and being converted at the box?

As for video image quality - When viewing each clip using either ZoomPlayer or WMP neither seems to be displaying any interlacing (interlace filters are set to off). Screen grabs provide perception that the 720p content is a bit sharper while conversely the perceived softening of the 1080i image tends to ever so slightly lessen the upsampling splotchyness.

[Brad]

Not sure how it works but can I suspect it's not true 720p as the actual incoming stream from Comcast is 1080i and being converted at the box?

KarMa already said it: most HD channels are 1080i, and the exceptions are basically every Disney and Fox channel. This doesn't change when the content they are showing happens to have originated as SD.

Let's say NBC is showing an old episode of SNL. They upscale it from 480i to 1080i, which requires deinterlacing + resizing + reinterlacing. They broadcast it at whatever bitrate. Your cable provider may or may not recompress to fit their own bitrate needs.

Then on your side, you have this 1080i 4:2:0 stream that's decompressed, upsampled to 4:2:2, 4:4:4, or RGB and sent over HDMI from your cable box. Your Colossus converts this to 4:2:0 and compresses to H.264.

Setting the cable box to 720p adds yet more processing: it needs to deinterlace and downsize. This deinterlacing may be better than what your player would do to the 1080i capture, but is likely worse given how low-effort cable boxes are.

If you could capture the native 480i NBC broadcast instead, you would avoid all of these processing steps. But usually SD is so horribly over-compressed that the upscaled feed is the lesser of the evils.

[Golem]

Thanks vaporeon800 for the additional (and reinforced) info. Since I don't follow the tech side of this until a need arises it sometimes takes a hammer for it to soak in. What you state makes perfect sense and reinforces my findings from earlier today about image quality of my test captures.

As it stands right now I'll be doing the following:
1. Cap HD 1080i & 720p no-flag using RNG/Firewire. Flagged will be fed to Colossus at broadcast resolution.
2. Cap SD 480i destined for DVD using RGN/Firewire (DVD-ready MPEG-2). Upscaled-only has to be Colossus and will be at HD broadcast resolution.

Should be fairly sorted. Thanks all!