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Thread: 544x480, etc: changing recording resolution

  1. #61
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    Originally posted by trekkerj
    Now if you set resolution to 0 on BEST quality, do you notice problems during Live TV?...I'm thinking to up it to 4800 and a constant bit rate....
    No, no problems at 720x480 and 5.8Mbps CBR. The only time I have ever seen glitches is with "Save Disk Space" (have tried it a couple/three times), and this is so unusual (blockiness & pixelation) that I turned it off.

    AFAIK the CBR numbers are not changeable in Tivo--if you know how to change your CBR for any resolution by all means let me know.
    Philips Standalone v3.01 w/2-80G drives and Tivonet.

  2. #62
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    Why would you say they aren't changeable? I just edited them like I editted the VBR in tivoweb.

  3. #63
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    Originally posted by trekkerj
    Why would you say they aren't changeable? I just edited them like I editted the VBR in tivoweb.
    Where do you edit them then? Specifics please.
    Philips Standalone v3.01 w/2-80G drives and Tivonet.

  4. #64
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    Sorry. Under Resource Editor, BitRates/AltBitRates, the setting for CATVBasicMAXBitrate for example is the CBR for BASIC Quality.

  5. #65
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    Doesn't work that way on my Philips SA--all my VBR and MAX bitrates are different from what I actually record at CBR (Save Disk Space off). If you have found a way to change the CBR using these fields then that's the first I've heard anyone being able to do it.

    So I have to press you--how have you verified the CBR of your recorded programs? MPEGPROP? DVD Patcher? Other?
    Philips Standalone v3.01 w/2-80G drives and Tivonet.

  6. #66
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    I verified it very easily. I set my BASIC quality MAXBitRate to 4000Kbps. I recorded a program with it (Save Disk space off) that was exactly 1 hr 45 min. 1.75 hours. Then just do the math.

    40000000 bps / 8 (8 bites per byte) x 60 seconds (per min) x 60 minutes (per hour) x 1.75 hours. The actual size of the file was exactly as the calculation predicted. Same for the default quality settings.

  7. #67
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    yah, setting the MAX bitrate under 2.5 sets the CBR. Note that you can have both CBR and VBR at the same time...

    if you set the MAX and VBR rates the same, the TiVo will record CBR even if 'save disk space' is enabled. you can verify this by watching /var/log/tvlog. This way you can have some record qualities CBR and others VBR.

    I've found that with a high quality digital source, VBR uses only slightly more bandwidth than whatever the digital signal was originally compressed with- ie with my TiVo running 9.8/9M and recording a low bitrate (X-files) DVD, my MAX bitrate was actually 5M, my average bitrate was 2.5M. I got nearly identical results running 5/6M VBR. I ripped the raw video from the DVD and checked it as well, and the bitrate/Q were almost identical as well.

    The tool I use for checking bitrate' is BitRate Viewer' from http://www.tecoltd.com. The free version shows you peak and average bitrate and Q. For 25 euro, you get the ability to generate reports, analyze the GOP structure and more. I'm quite happy with it.

    Where I have had problems with all this is with noisy, low quality analog sources. I have not yet been able to get satisfactory results with the TiVo directly, but transcoding using the MJPEG tools (and optionally filtering with yuvdenoise) under Linux has worked well. For the quality of my analog signals, 352x480 5M MAX, minimum Q = 8 does quite well. Of course this all takes CPU time, but I'm hoping to put together a Linux cluster of 733MHz Pentium 3 machines ($200 from WalMart :) to do the bulk of the work. I hope to just dispatch the video from different FSIDs to different nodes and then append all the outputs together and mux with an up-converted audio track.

  8. #68
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    Originally posted by khmann
    yah, setting the MAX bitrate under 2.5 sets the CBR...
    Well, I have 3.0 and this surely does not work for me. CBRs have always been reliably 5.8, 3.5, 2.6, 1.47Mbps as has been reported before. At least MPEGPROP and DVDPatcher confirm these, and some bitrate calculators I've used don't argue either.

    I have not tried doing the "MAX and VBR the same" trick but that seems to make some sense. Or maybe my tivoweb is behind a version or two? A v3.0 difference? I don't THINK it's "pilot error"; I thought I was wrong once years ago, but it turns out I was mistaken!

    Update: I feel really STOOPID! My MAXes are set at 5960, 3660, 2760, and 1630kbps, all of which are exactly 160kbps above my CBRs. So this is correct, changing these resulted in a change to my CBR'ed programs. It doesn't explain the 160000 difference in settings, where I might've expected a 192000 difference for the audio bitrate. Anyone know what this is about?
    Last edited by laserfan; 08-22-2002 at 06:07 PM.
    Philips Standalone v3.01 w/2-80G drives and Tivonet.

  9. #69
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    Originally posted by mccg
    Hi bato,

    You've got that wong....
    I haven't been to the vcdhelp site, so you may have misunderstood what they have written.
    Maybe SVCD is 352. S-video certainly isn't

    PAL TV resolution is about 768 (as they don't use pixels, you can't really talk about resolution)
    S-VHS has about 625 horizontal (which is why the logo has a small 625 in it)
    VHS (IIRC) is about 425.

    "PAL" DVD's are usually 720 (I know they are not PAL encoded, but they are designed for use on PAL TVs)


    I have managed to change the resolution, using the "Bitrates" section of TivoWeb 1.9.4 B3. Changing just the AltBitrates doesn't have any effect.
    But, it isn't useable, as the picture gets shifted about 2 inches to the left, so I get a big black bar on the right, with a green stripe at the far right, and the left hand edge is chopped off, eg: on BBC News 24 (widescreen) the clock, which is in the 4x3 safe area, is actually half off the screen!

    I have gone back to resolution 2 (480) :-(

    Cheers,
    Mike
    Hi there - first quote on the board - hope you'll bear with me if it is too long or not relevant. Haven't got a Tivo yet (it is in the post I hope) but I did work as a broadcast video engineer for a while, in digital video, so I thought I'd clear up some misconceptions about resolutions.

    Digital video, as used for MPEG 2 on most DVDs and most UK DTV runs at 720x576 (720x488/480 in the US) samples. Of these 702x576 co-incides with the equivalent analogue picture - there are 18 samples a line extra to allow for overshoot and undershoot in A/D D/A conversions without ringing.

    This is the same for both 16:9 and 4:3 full-frame transmissions (possible exception is 4:3 pillarbox in 16:9 frame tranmissions - which are effectivelya central 540x576 with the rest filled with black to fill the 720x576 frame) - the samples aren't square - and are different shapes in 16:9 and 4:3 modes! (Non-square pixels if you like)

    The common 768x576 resolution for "PAL" is actually the equivalent resolution for 4:3 if square pixels or samples are used. This is often the case with PC video grab cards designed to grab video for display on a PC with square pixels.

    The number of horizontal scan lines in a "PAL" video signal is always 625 (unless you are in Brazil). However not all of these are "active" - some are used for blanking, sync pulses and vertical interval data. In fact only 576 lines actually contain picture information conventionally. This is where the 625 vs 576 figures come from.

    S-VHS uses the small 625 to indicate this - this is not to do with its resolution as such - more to indicate that it is not a 525 (US NTSC machine). This is also because the S-VHS recording format, unlike VHS, is the same in both PAL and SECAM machines - SECAM machines transcode to and from PAL on Record and Playback. So there is no S-VHS PAL or S-VHS SECAM logo, unlike PAL and SECAM VHS.

    VHS in PAL and SECAM forms is also 625 lines (unless you are in Brazil) It records the same number of scanlines as S-VHS and DVD. Effectively DVD, VHS and S-VHS have pretty much the same vertical resolution - though the HQ and colour processing in VHS can reduce this through line averaging. (Video CD is the odd recording format out - as it runs at 352x288 resolution - effectively half the vertical and horizontal resolution of DVD, and half the vertical resolution of VHS and SVHS. It does this by effectively ditching one of the two interlaced fields - and halves the temporal resolution - i.e. motion portrayal is jerkier)

    The difference comes in how much information is in each line, the horizontal resolution. DVD/DTV potentially goes over 500 lines, SVHS equates to about 450 lines, VHS about 200. It sounds like you are confusing the horizontal and vertical resolutions of various formats.

  10. #70
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    I stand corrected

    Hi Steve,

    Thanks for that. I'll admit I was wrong...

    I had been told (a long time ago) that the 625 was for horizontal resolution (or is it called vertical definition for TV?), ie: number of "columns"

    I did think that it was an odd coincidence that we have 625 rows (576 of picture).

    So S-VHS is about 450 and VHS about 200.
    That makes more sense, and why the TiVo (at 544) looks better.


    I find that the 720 resolution setting is unusable on my UK TiVo, since the picture shifts about 3 inches to the left (on my Sony 28 inch Widescreen TV), and no amount of fiddling with the enginerring menus will recover all the picture, and there's a huge green bar down the right. (Just a 2 pixel line in 544 res, and outside the TV "window")

    It's especially noticable on videos I've downloaded to the PC, and I haven't found a (free/cheap) way of cropping the picture without losing loads of quality.

    Cheers,
    Mike
    Mike Gregory

  11. #71
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    Yep - incidentally - the BBC transmission area is entirely 16:9. This means that 4:3 material is converted to 16:9 for transmission - with large areas of black either side to make up the side bars. This limits the horizontal resolution of the 4:3 active area to 540 samples (within a 720 sample frame)

    Other broadcasters (C4/E4) don't do this - and change the aspect ratio of their presentation areas instead.

    The 720 sample setting on the Tivo causing problems sounds like a timing / clock rate kind of issue. Don't know enough about the chipset involved yet - will do some digging...

    (As for the vertical / horizontal resolution issue - I've lost count of the number of times I've seen this confusion... Consequence of "lines" being used as both a measure of the number of vertical scan-lines, and also the number of individual horizontal lines in the picture that can be resolved...)

  12. #72
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    Did anyone finaly?

    Did anyone ever find the exact setting needed for Phillips SA units to record at 720x480?

    Like the exact settings needed... Ive been trying the mix and match of settings out here on the board and have not had much in the way of results.

    Any help would be greatly appriciated.

    Thanks!

  13. #73
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    Set the resolution to '0'

  14. #74
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    Question

    I want to record everything in the highest possible resolution, but have it set for 720X480. I am not concerned about size of the files or space on the Tivo.

    This thread is long and confusing (To me at least). Let's say that I want to just change my "Best" setting to record at 720X480. Recordings I would extract would be only from the SVideo input.(DishNetwork).

    What would I need to change in the Resource editor.? Do I need to change the CATV and Rooftop settings? Or can I just change the DBS settings? If so, which ones?

    Please spoon feed the *****.... Thanks.

  15. #75
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    If you find this confusing, then you shouldn't be doing it

    Originally posted by bfdhe
    I want to record everything in the highest possible resolution, but have it set for 720X480. I am not concerned about size of the files or space on the Tivo.

    Well, your confusion starts from the fact that "720x480" and "resolution" describe the same thing.

    Please spoon feed the *****....

    The keys, presented many times in this thread, and now, once again, are, tivo lacks the power to record at the highest resolution and at the best quality, and here's an example of to what to set the resolution and quality.

    HTH
    Last edited by artships; 02-10-2003 at 01:54 PM.

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