Originally Posted by thomase
I posted a question about this in other theads but only got one response (and that was a while ago).
Ah, the confirmation from V.X.Donique in your Weird DCH3416 behavior
thread that they were seeing the same issue?
I'm seeing a strange problem with my Comcast 3416. The bottom few rows of pixels from the image are transplanted to the top of the image for HD signals.
On my DCH3416 (firmware 18.34), this happens for both HD and SD signals. It only occurs on the composite and S-Video outputs (and presumably coax -- haven't tried), not the component outputs (and presumably not HDMI either -- haven't confirmed).
It is only a few lines, so therefore it is not noticeable unless you have TV in a 1:1 pixel mode (sometimes called native, full pixel, 0% overscan, etc.).
Yeah, I use a 1920x1200 HDMI computer monitor with no overscan options as my HDTV, thus I see this.
This is NOT to be confused with the closed captioning data in SD broacasts. This also manifests as lines at the top of the image. It is DEFINETLY lines from the bottom of the image. It is especially easy to see when viewing a background that has a different solid color at the bottom compared to the top. For example, if you are viewing an HD picture that consists of the top half solid red and the bottom half solid blue, you will see a very thin blue line at the top.
Right. If you're watching an SD signal, though, you'll also see the closed caption encoding on the two scanlines below the bottom scanline which has been transposed to the top. This is how I came up against this issue. I was archiving some shows from my 3416 to DVD (via analog to DV capture with my Sony MiniDV camcorder), and since I was seeing the CC encoding lines in the picture, I was thinking that the captions would be preserved. However, I found that when playing back the DVDs on my old analog SDTV (with CC display enabled), no captions would result.
I was thinking that this was due to everything being shifted down one scanline by the one from the bottom being moved up to the top, but using Vegas, my video editor, to move the picture up or down one or more lines didn't seem to help. (However, I later realized that Vegas' Pan/Crop feature causes it to deinterlace interlaced signals, and in the HDMI not allowing Closed Captioning?
thread, it's mentioned that deinterlacing destroys the CC info, so this may not have been a valid test.)
I've tried a lot of searching to find out what line Line 21 corresponds to on a 720x480 DTV picture, but haven't been able to find anything. I've read that Line 21 is part of the Vertical Blanking Interval, which would seem to indicate it's not part of the visible picture at all, but I've seen CC signals on pure analog setups (can't remember if this was due to incorrect overscan adjustment or due to a rolling picture). The closest I found to the info I was looking for was http://www.cpcweb.com/nle/nle-hardware.htm
, which states that "Caption data sits in 720x486 video in Row 0, 1 or 2 depending on the NLE system". No info on the site about what happens if it's a DV-style 720x480 picture rather than 720x486, but it would sound like the CC lines would be excluded.
A weird thing is that when I connected my 3416's composite video out directly to my analog TV, closed captions would
be displayed. Yet when digitizing that same signal and putting on a DVD and playing that through the same TV, no captions. This made me wonder whether something in my video capture / editing / mastering workflow was breaking the captions, but given what I've learned since then, I'm wondering if it's actually the case that the DVR was outputting them in two places, one on the (invisible?) Line 21 where they're supposed to be, and another copy within the picture overscan region??
It goes away if the box is rebooted but eventually it starts happening again. It is definitely not a problem with the signal from the provider because it happens when playing back an HD recording from the hard drive. If I reboot, the replayed recording looks correct. After the "bug" shows up, the recording has the bottom lines of pixels transplanted to the top. So clearly this is a problem with the way the signal is sent from the box to the display.
Thank you for reporting that!! I hadn't realized my DVR wasn't doing this from day one. Sure enough, after doing a hard power-cycle of my box, I see that the scanline from the bottom is no longer "rotated" to the top, and the CC lines are not visible either. Well, at least they're usually not visible. If I hit Pause, I see them at the top (just the CC lines -- not the misplaced bottom scanline from before the reboot). When I unpause, I see that the DVR is duplicating the third and fourth scanlines to the top to cover up where the CCs would be. This sometimes introduces noticeable picture artifacts. This only occurs over the S-Video (and presumably composite) out(s) -- over the component out (which I guess I should mention is going into a Denon AVR-888 and from there via HDMI -> DVI to my NEC 2490WUXi LCD monitor), the top two scanlines are the unmolested CC encoding lines. (Great, so I can't get them on the output I use to make DVDs, and am forced to have them on the output I use to view TV, where they serve no purpose for me other than to annoy.)
If the're no way to get the Closed Captions to be operable on my DVDs (I also tried various experiments with SCC Tools
, to see if I could extract the CC info and convert it to DVD subtitles, but never managed to successfully extract any captions), I'm sorry I didn't manage to find your post sooner, as I've already made a bunch of DVDs with visible (and annoying, on 0% overscan displays like mine) but useless encoded captions. While the scanline duplication after the reboot can result in visible artifacts, it's certainly a lot less noticeable than the CC lines.
BTW, not really on topic, but another thing about this DVR that annoyed the crap out of me is that by default the stereo analog audio outs are set to mono output. How ridiculous a default is that?? Unfortunately I had archived off a bunch of shows to DVD (deleting the HD copies) before I discovered this.
I'll make one more note which is an important one. I have an HD DVR box, but not an HDTV. I just have a regular 27" crt connected to the DVR via s-video. If I tune to an HD channel, the box downconverts it to 480i letterbox over s-video. It is quite possible that this problem is very specific to my situation because I am a.) downconverting and b.) using s-video.
Has anyone else seen this?
I haven't figured out which sequence of repeatable events causes this to happen. I have never witnessed the change while watching an HD channel. It seems to only show up at some point after switching to an HD channel after coming out of standby or switching from an SD station.
I was thinking maybe it would be triggered by turning on viewing of CCs with the DVR menu, but no dice.
Has anyone else seen this?
Edit: I'll admit that it only occurred to me that the problem could be related to HD->480i downconverting when I was almost done writing this post. At the beginning, I mentioned that you'll only see the problem with 0% overscan mode. I should rather say... if this problem is NOT limited to just HD->480i downconvert, I'd imagine that you won't see it on an HD set unless you have 0% overscan. With my particular setup, I see the transplanted scanlines within the inner letterboxed portion of the image on my SDTV. In other words, from top to bottom in order I see, 1.) top black letterbox bar, 2.) transplanted scan line(s), 3.) normal image, 4.) bottom black letterbox bar.
Yeah, at first I thought maybe my MiniDV camera was doing the scanline transposition, until I saw that it happened for letterboxed HD signals as well, at the top of the widescreen picture region rather than at the top of the 4:3 frame.
So I assume there's no way to preserve Closed Captions when archiving content from this DVR, other than turning them on with the DVR menu, recording the video with and without them on, and then setting up the footage on the DVD as multiple angles?
Short of that waste of DVD capacity, I guess I would have to bite the bullet and pay the big bucks for a TiVo and use SCC Tools / ccextractor conversion to DVD subtitles to be able to preserve the CCs from directly exported MPEG files (and put up with not being able to record the SDV channels until Cox OC finally makes the tuning resolvers available here)?