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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 17 Feb 2015, 06:52 |
Absolute fan |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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I've done some pre-demodulation cleanup to more closely match what LD players actually did, and it improved color saturation a lot. Megapixie - on the color bar test you should analyze RGB levels/color saturation as well as signal/noise ratio. Both my previous version and the 4300D have similar undersaturation which leads to off colors. The 2950 is better, so maybe it's something they did to get such high frequency response on the 4300D...? I also changed the NR to be standard noise coring, and reduced it's strength to 1 IRE luma only. (If 1 IRE is enough for VE, it's probably enough for anything but the noisiest disks...) This is the same type of analog noise coring many players use (their usage of it depends by model, though... some only use it on CLV and the early bits of CAV disks - others like the S1 have it enabled all the time, even in test mode) (For another aside, per the service manual the RCA SJT-400 CED player has an undefeatable 5 IRE coring.) New screenshots, with the least flattering (zone plate) shots first, and the best (cleaned-up ballerina shots) last: http://imgur.com/a/JQDql - 1IRE NR http://imgur.com/a/wVQm3 - no NR edit: Looked again at the original de-emphasis timings which boosts frequency response - at the expense of overshoot. Made it an option for ld-decoder.py (-h) - samples here: http://imgur.com/a/pxNOS
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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Guest
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 17 Feb 2015, 12:04 |
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Awesome stuff HC.
You are quite right: I've never looked at chroma phase/saturation. Once I've got up and running with capture - I'll do another article.
I'll take a look in a bit and re-run the numbers.
Mega.
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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 19 Mar 2015, 07:55 |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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Starting to figure out how to use OpenCV and took a first pass at optical flow-based 3D comb filtering - samples from VE here: http://imgur.com/a/3t5nD#QWfTXx1Also improved the RF capture driver by turning off the s-video chroma ADC, and slowly working on PAL LD decoding thanks to samples from robwhar and megapixie. Much more discussion etc over on the google doc.
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 08 Apr 2015, 17:21 |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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Here's the 1986 Laservision demonstration. I improved my post-decode encoding settings (h264, flac audio, yadif+mcdeint) in addition to the other tweaks I've been doing on the way. Audio's slightly regressed because I turned down the filtering and tried to speed it up, and it's got some pops/distortion (or it might just be the disk is a little scratched) Digital sound isn't nearly finished yet, but being worked on. And from a purely preservation point of view, digital tracks can already be saved without RF decoding. https://www.youtube.com/watch?v=JXQcPwLpqwo - 720P is recommended for 60P deinterlacing.
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 13 May 2015, 07:06 |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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Been playing with PAL a bit - I don't have a working comb filter yet alas, but I'm making some headway. On a lark I got a cheap PAL disk off eBay (Eric Clapton's Unplugged - which I have an undocumented WEA US pressing of that I need to look at ) and the CLD-V2800 can be persuaded to 'play' it in test mode for at least a bit without puking (outside of test mode for ~30 seconds or so until it goes ) , and I can process it's RF (the odd look of it's from the opening screen and not a software glitch )
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 17 May 2015, 21:38 |
Absolute fan |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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Thanks (and thanks for all your help/motivation, too!) Got the PAL comb filter somewhat working today: http://i.imgur.com/ewuEDTx.pngedit: new samples http://imgur.com/a/YS1VA
Last edited by happycube on 19 May 2015, 06:46, edited 1 time in total.
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 23 May 2015, 16:29 |
Absolute fan |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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ld-decode: http://i.imgur.com/eZ7GChe.pngfrom http://notonbluray.com/blog/ - 2950: http://notonbluray.com/blog/wp-content/ ... n-bars.png4300d: http://notonbluray.com/blog/wp-content/ ... n-Bars.pngI don't think the potential of PAL LD was ever properly tapped (a CLD-97 level player would have been great, much less an X0-level one!), hopefully ld-decode will show a bit more of what it can do. But I will need to decode digital audio and implement an adaptive 2D comb filter. I got my PAL Cape Fear today and I've had some success improving the TBC to handle it better. There are definitely still glitches (one single-line error every few frames), but given that all the servo systems are probably degraded while playing a disk the player wasn't meant to play at all, it's quite good. (That said, I'm glad I didn't spring for that set of PAL disks on eBay US) --- I found an existing project from 2005 to decode CD audio last week and got in touch with it's creator (the source is now on my github as cd-decode), and hopefully soon CD and digital audio will be decoded. Looking at a raw capture from a CD now and still working out the filtering, which is kinda worrysome for the LD digital audio case since much more filtering is required. But it's definitely possible, and having code to handle the subcodes etc is a big help.
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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happycube
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 31 May 2015, 17:09 |
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Joined: 18 Apr 2012, 18:02 Posts: 1614 Location: United States Has thanked: 71 times Been thanked: 88 times
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My current setup is ~28.636mhz@8bit, the 50-56mhz@12bit is just what I'd like to have I don't think you can go much below 27, you need 2x the frequency you're trying to capture. (might be different capturing IQ) The 14mhz is actually 4 times the NTSC color carrier frequency (~14.318). It's much easier to run a digital comb filter at that frequency for phase/calculation reasons, so the TBC and a lot of other stuff is timed off it. BladeRF with the upverter board would be nice, but it's about $500-600 more than I can afford right now
_________________ Happycube Labs: Where the past is being re-made, today. [meep!]
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dewdude
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Post subject: Re: (WIP) Laserdisc software image decoder from raw signal Posted: 31 May 2015, 20:38 |
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Joined: 24 May 2012, 02:18 Posts: 193 Location: Manassas, VA/Northern Virginia/DC Metro/United States Has thanked: 0 time Been thanked: 2 times
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happycube wrote: you need 2x the frequency you're trying to capture. (might be different capturing IQ) Much different capturing in I/Q, your sample-rate basically equals your actual bandwidth. So 1msps actually captures 1mhz rather than 512khz as shannon nyqist tells you. However, you're dealing with two signals vs just one; one channel is in phase with the LO and the other is 90 degrees out of phase with the LO and the system is able to determine positive or negative deviation from center. So if you need 28.636mhz; you can do it with a 30msps ADC that uses I/Q (quadrature) sampling. I came from the digital audio world, where Shannon-Nyquist fully applies; *granted* you're still effectively using same data rate (since you have two channels of information)....if your ADC can only handle 30msps, at least your stuff will handle 30mhz.
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