On Sun, Apr 14, 2002 at 12:07:47AM -0500, Billy Biggs wrote: > > I mean that you record at like 352x240 @ 59.94 (both fields) or 29.97 (lose a field)? > so that you don't get > interlaced frames, You store each field as a frame then record at 59.94? Do you play them back at 59.94 "stretched" (keeping field dominance in mind) or do you lay them onto the video device interlaced one after the other, alternating each frame into an interlaced field, to mimic the way TV really works? > or you record to MPEG1 which is a progressive format > (you can't record interlaced frames without colour bleeding between > them) and so it's been deinterlaced. My point was that I don't think > any of the recorders out there are tuned to recording interlaced streams > to an interlaced format (like MPEG2 in interlaced mode). Indeed. > For example, notice how the chroma from the bttv driver at > bigger-than-single-field resolution in 4:2:0 mode is in the wrong format > for MPEG2's interlaced mode. Sorry, my knowlege of video doesn't go that deep. I will take your word for it though. :-) > In order to record TV for compression to > interlaced MPEG2, I need to grab frames in 4:2:2 mode and downsample the > chroma myself. OK. Note that mp1e says this: Filter 'YUYV 4:2:2 w/vertical interpolation' Image format 'YUYV' 640 x 480 granted When I record at 640x480. > My test recorder app is the first I've seen to do this, > which tells me that either a) nobody else knows (but I did post on this > list about this problem), or b) nobody else cares about recording > interlaced streams from V4L sources (yet). I assume the latter (b). I think that the idea of reproducing exactly the interlaced signal is not there yet. Everybody wants to play (and copy) DVDs to their monitors right now. Nobody (in a position to understand and write the software) is really looking for the "killer vcr" yet. > Well the drivers aren't good enough to allow you to watch interlaced > video on the G400 TV output. Meaning there is no way to output fields, alternately, interlaced @59.94Hz with the current G400 drivers? > Timecode is a standard for noting the time of each frame. OK. That is what I thought it was. > Yes, I use Xv for scaling. But I'm sending 720x480 @ 59.94fps @ 16bpp > (that's 4:2:2, so the same colour quality as a TV natively). Why 480 lines @59.94? I would have thought it would be 240 lines at 59.94 or 480 at 29.97. But using your numbers, I calculate 331,444,224 (316M) bps, or 39MB/s to the video card? Is that right? I can see why it might judder then. :-) > That's > alot of data, much more than twice the bandwidth of a DVD. Indeed! > Very few of the Xv drivers use DMA to > transfer frames into video memory, and there's little demand since I > seem to be the only app to be sending this much data. I hear ya. > The judder problem is something else that needs to be fixed. For > playback of 59.94fps video without judder I need to basically > software-genlock the monitor to either 59.94hz or 119.88hz Right. The G400 does/can do this. > It would be nice if > more people were interested in stuff like this, but I find it hard to > convince people that these problems need to be solved. Like I said, I think they are all busy playing DVDs. :-) I think also, perhaps, people are just accepting of the lower quality of "TV on the computer". > Well I thought mp1e only records MPEG1. To my knowlege, yes. > Maybe it's deinterlacing. I think the Filter 'YUYV 4:2:2 w/vertical interpolation' Image format 'YUYV' 640 x 480 granted suggests that it is. > Also 640x480 I wouldn't consider full resolution, Right. > it would be nice to > get at least 720x480, and maybe even 720x486. Let me play with 720x480. What difference do you think I should see between 720 and 640 considering my TV out is 800x600? My bttv card does not support 486 as a height though. > Sure you need it. You want it if you're recording anything from film > source to convert it from 59.94fps to 23.976fps. 59.94fps at M x N to 23.976fps at M x N*2? > It makes watching > films much smoother and MUCH better quality, I guess I am a philistine. I have never noticed watching films on TV any worse (other that picture size and clarity) than watching real film or DVD. :-) How do I know when recording something from cable that it would need telecining? If some stuff is sourced from video tape and some from film, by the time it gets to me, how do I know? > You need to record it as an interlaced stream and remember the field > dominance (are your recorded frames top-field-first or > bottom-field-first). Then, when you output to your G400, you need to > make sure it plays the fields back in the right order. So you are saying pretty much what I was then? Record in the format it was broadcast and play it back from the recording in the format it was broadcast. No conversions between to turn fields into frames and all that crappola. > The point is you > need a better API than just running mplayer on the second CRT which > happens to point at your G400. The V4L2 API might be good enough, but > nothing supports it yet. I see. > Also, AFAIK when mplayer (or whatever) talks to your CRT2, it's > sending RGB. Ideally you'd want to talk directly to the TV encoder and > feed it the raw Y'CbCr data etc.. I can understand why that would be better. > All of this means better drivers than > the current set. Indeed. > I keep meaning to do it, but I've been busy with > school. But now that I'm almost done, I'm considering buying a more > modern video card and getting it to work instead... What are you considering buying that will support all you want to do? b. -- Brian J. Murrell
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