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  1. This is my first quick intro to my capture setup. If there's enough interest and it survives sharp shooting from the crowd here, I'm tempted to do a more thorough run of documentation. Lossless VHS captures (ffv1/flac) and compressed post processed (h264/aac: IVTC, crop, resize, normalize audio) captures are attached.

    What do you think of the quality? Is there a test or benchmark tape out there you’d like me to test my setup against? Anyone have a tough tape they’d like me take a crack at?

    Equipment:
    JVC HR-S2902U ($59.95)
    Sony Handycam CCD-TRV85 ($49.99)
    EVAL-ADV7842-7511P ($216.41)
    AJA KONA LHi ($119.00)

    Signal flow is VHS/Hi8 (TBC/DNR disabled, edit mode) -> EVAL-ADV7842-7511P (Line and Full frame TBC enabled, 10-bit 422 out) -> AJA KONA LHi (lossless) -> ffmpeg archival and display copies

    I've experimented with:
    AJA KONA LHi (ADV7403) direct - solid captures unless there's non-standard signal, appears to use line TBC-like functionality
    BlackMagic Pro Capture 4k (ADV7180) - garbage, could not capture more than a few frames at a time, poor quality
    Magewell Pro Capture HDMI (ADV7842) - very good performance! appears to use line and frame TBCs, however captures seemed 'washed out' or had bad default levels, strange gaps in histograms. I'd pick this. Must disable default deinterlace. 24 bit / 48kHz audio would be nice too.
    BlackMagic Decklink Studio 4k (ADV7842) - while having the fancy ADV7842, the latest firmware/drivers clipped outside of broadcast levels and support hasn't fixed it in years, randomly drops a handful of frames with no explanation


    Since TBCs are historically a point of friction. If you believe the marketing:

    "The ADV7842 implements a patented Adaptive Digital Line
    Length Tracking (ADLLT™) algorithm to track varying video
    line lengths from sources such as a VCR. ADLLT enables the
    ADV7842 to track and decode poor quality video sources (such
    as VCRs) and noisy sources (such as tuner outputs, VCR
    players, and camcorders). Frame TBC ensures stable clock
    synchronization between the decoder and the downstream
    devices."
    https://www.analog.com/media/en/technical-documentation/data-sheets/ADV7842.pdf
    https://www.analog.com/media/en/technical-documentation/application-notes/237557357AN_850.pdf
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    Last edited by petet; 7th Nov 2019 at 20:39. Reason: Magewell does capture 10 bit!
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  2. Mountains of gear vaporeon800's Avatar
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    Ooooo. Do you still have any of the other three cards for comparison?

    It would be great to see the strength of the line TBC with some (horizontally) jittery home recordings. I've wanted to try that eval board myself, but I've been burned a few too many times by big marketing claims that just didn't hold up when put to the test.

    EDIT: Regarding Magewell Pro Capture HDMI, supposedly they indicated that the TBC functions are not enabled:
    Originally Posted by FLP437 View Post
    After contacts established between another member and Magewell , Magewell apparently clarified that they do have choose not to implement the Advanced time-base correction (TBC) with frame synchronization and 3D comb filter even if these features are integrant part of the ADV7842 ( main card chipset ) and all requirements were met namely memory in excess of 128 MB ( card has 256 MB fast in board memory). Apparently they choose instead using the significant amount of memory installed to implement a multiple buffer system that they say completely avoid lost frames if the transfer speed is enough. As the interface is PCIe 2.0 transfer speed is really not a problem. Related to the 3D Comb I tried using the Snell & Wilcox tests a capture using the composite input and it seems indeed that the 3D comb filter is also inactive.

    It´s a pity as apparently according to http://forum.lddb.com/viewtopic.php?p=81549#p81549 the 3D comb from the ADV7842 it´s the best ever. It seems that analog is really not a priority for the capture card makers in this moment and even when they have the possibility to make an outstanding card in what analog is concerned they choose to prioritize digital and neglect analog.

    Even so I continue to find this card to be one of the best in its class.
    Last edited by vaporeon800; 5th Nov 2019 at 00:09. Reason: Meant to note FLP437's post regarding Magewell
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  3. Member dellsam34's Avatar
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    Why not 720 non square pixels instead of loosing almost 100 pixels from the horizontal resolution just to have square pixels ? I would be skeptical about a line TBC that works outside the VCR, seems to be technically impossible to me but I could be wrong.

    One question, I see on EVAL-ADV7842-7511P board the digital output pins out of the Y/C (S-Video) ADC labeled HS/VS, Field/DE and clock, what kind of digital stream that is? If there is a way to convert those pins to USB I may get one to experiment with.

    Edit: I see the board has a USB port and can be connected to a PC, what kind of software is used to capture analog video?
    Last edited by dellsam34; 5th Nov 2019 at 00:01.
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  4. Mountains of gear vaporeon800's Avatar
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    On close inspection, I see what appears to be an AGC effect, but I don't have Star Wars on hand to confirm that the VHS itself isn't to blame.

    It's most obvious on fields 609-611 of Trust your feelings.mkv but happens elsewhere too. These three fields come from the same film frame and "should" be identical, but there is a large brightness shift from 609 to 610 and then a small shift from 610 to 611.

    Similar effect at 624-626 and 749-751 if you view with Histogram, and 762 vs 763.
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  5. I still have the BlackMagic Decklink Studio 4k. Will do a comparison shot (I use an older firmware to avoid the clipping issue), I'll also do one from the AJA directly. Was this clip 'representative' enough? Will find my roughest home VHS as well.

    Regarding Magewell Pro Capture HDMI, supposedly they indicated that the TBC functions are not enabled
    Tracking that thread, the reason I got one in the first place! - my only evidence I have is based on tuning those options in the EVAL-ADV7842-7511P. When I turn off line TBC, capture starts dropping frames. When I turn off the frame TBC, I can't capture my default VHS/Hi8 blue screens (before pressing play on tape). I assume this is because those signals are no quite clean/standard? Magewell captured all just fine. Also, support is unreliable... BlackMagic refused to confirm whether their card had TBC-like functionality. Proprietary. Even though they tried to advertise it in 2015 (https://web.archive.org/web/20150318095411/https://www.blackmagicdesign.com/products/intensitypro4k).

    Why not 720 non square pixels instead of loosing almost 100 pixels from the horizontal resolution just to have square pixels ?
    Mainly for max comparability - not all players/devices respect non-square pixels. Also fits web distro model, 640x480 is more common - maybe I break that with the 60p... Also, courtesy of the infallible Wikipedia "NTSC VHS is roughly equivalent to 333×480 pixels luma and 40×480 chroma resolutions" - hopefully I just averaged a little bit of noise out.

    I would be skeptical about a line TBC that works outside the VCR, seems to be technically impossible to me but I could be wrong.
    All I have is their documentation - seems more legit than marketing material, but I'll see if I can find a messier VHS help show this.

    On close inspection, I see what appears to be an AGC effect
    Good catch! I ran through the settings and thought 'automatic, ooo, that's good, I trust it to make good decisions based on random material I'd rather not fine tune'. The 'recommended' used in many of their scripts is manual. Not sure if this is a net gain/loss. Need to read more. I have "Enable chroma gain based on burst power" and "Enable luma gain based on the sync" both turned on.

    One question, I see on EVAL-ADV7842-7511P board the digital output pins out of the Y/C (S-Video) ADC labeled HS/VS, Field/DE and clock, what kind of digital stream that is? If there is a way to convert those pins to USB I may get one to experiment with.

    Edit: I see the board has a USB port and can be connected to a PC, what kind of software is used to capture analog video?
    That gets embedded in the HDMI output as far as I'm tracking (once digitized and corrected if needed). The serial and USB connections are the same - though serial is more reliable. You can use Advantiv AVES Blue or the serial terminal to directly control the board. Video is output though HDMI. I capture with AJA card. As for redirecting pins... there's a load of jumpers on there I haven't played with that allow you to reroute signals.

    EDIT:
    There's a lot of settings...
    https://www.analog.com/media/en/technical-documentation/user-guides/UG-214.pdf
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  6. The video is a film source. It should be inverse telecined back to the original film frames at 23.976 fps, not deinterlaced to 60p. Your 60p video has a duplicate frame pattern of 1 1 2 2 3 3 4 4 4 4 5 5 6 6 7 7 8 8 8 8... making it jerky. I noticed the AGC problem too.
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  7. Originally Posted by petet View Post
    I can't capture my default VHS/Hi8 blue screens (before pressing play on tape). I assume this is because those signals are no quite clean/standard? Magewell captured all just fine.
    Many VCRs often a 240p signal for the menu/OSD (maybe to avoid jittery text on a CRT), a non-standard signal not all A/D chips handle equally well. Aditionally, some devices like the JVC SVHS vcrs simply route the full composite signal output from the OSD chip on both the Y and C channels, it's possible that may also cause issues.

    Using an Eval board as a TBC/Capture device is an interesting idea, it gives you pretty raw access to all the settings of the capture chip.
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  8. Member dellsam34's Avatar
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    Originally Posted by petet View Post
    That gets embedded in the HDMI output as far as I'm tracking (once digitized and corrected if needed). The serial and USB connections are the same - though serial is more reliable. You can use Advantiv AVES Blue or the serial terminal to directly control the board. Video is output though HDMI. I capture with AJA card. As for redirecting pins... there's a load of jumpers on there I haven't played with that allow you to reroute signals.[/url]
    Oh I see, it is a HDMI output only. This card seem to have a lot of potential (comb filter for LD, line and full frame TBC's for VHS). I wish in the future they make a USB 3.0 version for lossless capturing from composite/S-video/component so USB can be used for both data transfer and configuration.
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  9. Mountains of gear vaporeon800's Avatar
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    Originally Posted by dellsam34 View Post
    This card seem to have a lot of potential (comb filter for LD, line and full frame TBC's for VHS). I wish in the future they make a USB 3.0 version for lossless capturing from composite/S-video/component so USB can be used for both data transfer and configuration.
    The eval board is aimed at engineers designing devices around the chip. It's not intended as an end-user product. Analog Devices doesn't make those themselves. And companies like Magewell that incorporate the chips don't offer access to all of these engineering settings.
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  10. Member dellsam34's Avatar
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    I see, I know the BlackMagic mini converter analog to SDI has the exact same chip but most of those features don't show up in the MediaExpress application, Wonder if a third party company makes a USB capture device with that chip that takes advantage of all those features in capture software instead of the eazycrap that sells everywhere? I don't mind paying a premium price for a capture device that works with modern OS's and geared towards consumer quality video sources.
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  11. The video is a film source. It should be inverse telecined back to the original film frames at 23.976 fps, not deinterlaced to 60p. Your 60p video has a duplicate frame pattern of 1 1 2 2 3 3 4 4 4 4 5 5 6 6 7 7 8 8 8 8... making it jerky.
    Correct - I IVTCed it and duplicated frames up to 60 fps. This is because the IVTC isn't perfect, I capture previews, commercials, etc that are interlaced - this is the best method I know of to handle mixed content. I use ffmpeg's fieldmatch to do this (https://ffmpeg.org/ffmpeg-filters.html#fieldmatch). This leaves whatever it detects as interlaced (isn't always right) and passes it to a normal deinterlacer. I use bwdif for this (https://ffmpeg.org/ffmpeg-filters.html#bwdif) Is there a better way that isn't manually intensive?

    Back to the AGC - what are your thoughts? Yes it might have visible issues when you are looking at material like this because it has duplicate frames in analog. But does it help in other areas with degraded/home tapes that might have some signal or recording issue? Could run some tests, but wondering if anyone had some more robust anecdotal experience. EDIT: see page 102 of https://www.analog.com/media/en/technical-documentation/user-guides/UG-214.pdf. I'm using AGC with white peak adjustment.

    Many VCRs often a 240p signal for the menu/OSD (maybe to avoid jittery text on a CRT), a non-standard signal not all A/D chips handle equally well.
    That's my guess! Happens on the Sony as well. I've since moved to emulation so no old consoles to play with other 240p sources!

    I see, I know the BlackMagic mini converter analog to SDI has the exact same chip but most of those features don't show up in the MediaExpress application, Wonder if a third party company makes a USB capture device with that chip that takes advantage of all those features in capture software instead of the eazycrap that sells everywhere? I don't mind paying a premium price for a capture device that works with modern OS's and geared towards consumer quality video sources.
    I feel your pain, hence all the boards I went through looking for this result. If you want USB3, then you just feed the HDMI out to a USB3 HDMI capture. All lossless still (assuming it doesn't butcher or crop or alter the signal for no reason). It isn't plug and play - but with a USB to serial, the software, the scripts, and a couple reboots if it isn't playing nice and you're in business. HOWEVER, this dev board does not embed audio - you need to capture audio separately. I'm using AJA to capture HDMI and combine with analog audio input.

    While I sort through some non-identifying home videos, this might suffice for dirty video. Fast-forwarded, paused and stopped video attached! Ooof, the IVTC/deint/60p does look choppy here.

    If anyone has good arguments for or against AGC, please post! Trying to commit before I burn through more tapes . Or anything better for mixed content through ffmepg.

    Want to give a shout out to QCTools (https://mediaarea.net/QCTools), its what allowed me to do all the pixel peeping for my assessments (and hopefully not miss AGC artifacts! Maybe need to read more of this: https://bavc.github.io/avaa/)
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    Last edited by petet; 5th Nov 2019 at 18:30.
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  12. Tried to find an older tape... how about some Solo flex? Here is someone else's capture for comparison: https://www.youtube.com/watch?v=GRWkEMX3aJ8.

    If someone else has a tough tape to capture and doesn't mind paying postage or the utter risk of it disappearing from the face of the earth forever, I can do a comparison capture for you. Please no sticky, flaky, moldy or otherwise physically damaged tapes that could gum up a VCR. PM and I can share a shipping address or potential local exchange.
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  13. Member dellsam34's Avatar
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    Originally Posted by petet View Post
    I feel your pain, hence all the boards I went through looking for this result. If you want USB3, then you just feed the HDMI out to a USB3 HDMI capture. All lossless still (assuming it doesn't butcher or crop or alter the signal for no reason). It isn't plug and play - but with a USB to serial, the software, the scripts, and a couple reboots if it isn't playing nice and you're in business. HOWEVER, this dev board does not embed audio - you need to capture audio separately. I'm using AJA to capture HDMI and combine with analog audio input.
    I have the BrightEye 75 with SDI out coupled to the PC with BM UltraStudio SDI to USB 3.0, One section in a home video tape is kicking my ass, no matter what I use it still has a frame roll, It is a PAL tape though so you can't help me in there unless you happen to have a PAL VCR. Other than that I'm happy with my capture setup, I can capture Betacam as well since I have an SDI input on the BM.
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  14. Mountains of gear vaporeon800's Avatar
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    Those random garbage jump-back frames in the middle of the post-Fast Forward playback in FFWD.mkv are unfortunate. Two seconds have passed since the end of Search, but it's still acting unstable.
    Image
    [Attachment 50785 - Click to enlarge]
    Image
    [Attachment 50786 - Click to enlarge]


    Do you have a second VCR to create a multi-generation tape? That's one stress test for TBC: https://forum.videohelp.com/threads/383020-In-depth-TBC-comparison-with-bad-VHS-%28video-samples%29

    You could also do it VHS → Hi8 → VHS if you have a spare 8mm tape.

    Also, are you able to centre the horizontal capture area with your scripts? The right edge is slightly cropped in favor of extra black on the left. Acuozzo / AntcuFaalb posted the same question to AD's forum at one point: https://ez.analog.com/video/f/q-a/7136/eval-adv7842-7511-questions-laserdiscs
    Last edited by vaporeon800; 6th Nov 2019 at 03:06.
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  15. Good call on the multi-gen tape! I'll see if I can put one together today.

    And yes - not sure about how that stabilization period compares to other TBCs or if it is due to the VRC itself, could try with Hi8 player.

    As for centering, yes it is possible - however I've noticed that by default the dev board aligns what it thinks is the active part of the frame to the right. This means I can always do a left 16 pixel crop of the horizontal blanking for every tape at 704x480 (https://en.wikipedia.org/wiki/Standard-definition_television). This looks good 80%+ of the time without having to manually dial in my crops, good enough for viewing and I always have the raw to go back to if needed. You can also sometimes see a tiny fuzzy edge a pixel wide so you know its not cropping any of the active frame. So while it doesn't look as good raw, it makes bulk cleanup easier after. I did solve the issue of it shifting the video up and cropping the top, that for sure was losing the top of the frame. Now it just has the extra 6 pixels that AJA likes to capture at 720x486.

    BrightEye 75 with SDI out coupled to the PC with BM UltraStudio SDI to USB 3.0
    A little jealous... I haven't found one cheap enough yet. I think it has the adv7403 right? So it uses this probably for a line-like TBC and it has an additional custom frame TBC on top it?
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  16. Member dellsam34's Avatar
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    Can you overdrive the capture resolution in that eval board above the normal standards? Like setting the capture resolution to whatever resolution above the legal standard of 720x480 (say 780x525) so that when the output comes out from the eval board at 720x480 it will be only a clean video frame with no other signals or borders showing in the frame? To rephrase my question, does the eval board do a hardware crop? Kind of like a telecine scanner of a film, set the film gate to see the whole film strip but the recorded frames show only the active picture area.

    The purpose of my question is to see if it is possible to devote more resolution to the active video area without having to crop in post and reduce the resolution of the video to a non standard one or live with permanent black borders.
    Last edited by dellsam34; 6th Nov 2019 at 12:21.
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  17. Can you overdrive the capture resolution in that eval board above the normal standards? Like setting the capture resolution to whatever resolution above the legal standard of 720x480 (say 780x525) so that when the output comes out from the eval board at 720x480 it will be only a clean video frame with no other signals or borders showing in the frame? To rephrase my question, does the eval board do a hardware crop? Kind of like a telecine scanner of a film, set the film gate to see the whole film strip but the recorded frames show only the active picture area.
    Maybe... haven't messed with those yet. You'd have to tweak it for every capture right? I've noticed each tape has a different border and alignment.

    https://www.analog.com/media/en/technical-documentation/user-guides/UG-214.pdf
    The SDP extracts HSync and VSync synchronization that are embedded in the video data stream. The SDP does not support external
    HSync and VSync inputs. The synchronization extraction has been optimized to support imperfect video sources, such as VCRs with
    head switches. The extracted HSync and VSync synchronization is then used to drive the digital resampling section to ensure 720 active
    pixels per line are output by the SDP.

    The ADV7842 uses a VSync and HSync PLL to provide an accurate and reliable lock for both perfect and imperfect video sources.

    • VSync PLL: provides extra filtering of the detected VSyncs to give improved vertical lock.
    • HSync PLL: designed to filter incoming HSyncs corrupted by noise; providing much improved performance for video signals
    with stable time base but poor signal to noise ratio (SNR).
    Two registers, SDP_EXTEND_VS_MAX_FREQ and SDP_EXTEND_VS_MIN_FREQ, can be used to additionally extend Vsync lock
    ranges.
    How about some Soloflex Vol. 3: repeatedly remastered for an improved audio visual experience! (no sound and the below signal flow)

    UNKNOWN TV Source -> COAX? -> VHS -> COMPOSITE -> Hi8 -> COMPOSITE -> VHS -> COMPOSITE -> Hi8 (overwrite) -> COMPOSITE -> VHS (overwrite) -> S-VIDEO -> CAPTURE
    Last edited by petet; 6th Nov 2019 at 20:23. Reason: Clicked 'advanced' and removed attachments. Now if I could only delete a post...
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  18. Just wasting space on the server here, sorry! Didn't see an easy way to edit and remove. Uploaded the old cuts. These are the correct ones.
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  19. Originally Posted by dellsam34 View Post
    I would be skeptical about a line TBC that works outside the VCR, seems to be technically impossible to me but I could be wrong.
    Not really, main thing the line TBC does is looking at the signal and trying to determine a the horizontal sync pulses as accurate as possible, i.e where a line starts and ends, and resizing each line appropriately. When I looked at the SM for my NV-HS1000 and my JVC SVHS decks, they didn't seem to use anything internal to the VCR and they operate on the demodulated and processed video signal before going out of the VCR. In theory they could maybe look at the phase/frequency of the color signal or stabilize the video before upconverting color to maybe help make things a bit more accurate but I don't know if any VHS decks do that. May be more usable on betamax and 8mm, as I think they have a pilot tone at a specific frequency that could be of help for the TBC which may be used, though I haven't looked into the schematics of those. I think some of the broadcast JVC and Panasonic VHS decks may have more advanced TBCs that can do a bit more like improve dropout compensation etc.

    A whole other issue is TBCs used on full composite signals like the older open reel broadcast tape formats. Color-under formats like VHS, 8mm, betamax, umatic etc. makes use of the fact that the color is separate from brightness on the tape to compensate for phase/frequency instability on playback when converting it up to the broadcast frequency that can be decoded by the video capture chip or CRT screen.
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  20. Mountains of gear vaporeon800's Avatar
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    I was expecting a lot worse from a fifth-generation video. There are obvious little wiggles if I look at the windows field-by-field, but in motion my brain just blurs them together with the tape noise.

    Can you also capture it with the KONA directly, for comparison?

    Maybe I can come up with a tape to mail to you.

    Originally Posted by oln View Post
    When I looked at the SM for my NV-HS1000 and my JVC SVHS decks, they didn't seem to use anything internal to the VCR and they operate on the demodulated and processed video signal before going out of the VCR. In theory they could maybe look at the phase/frequency of the color signal or stabilize the video before upconverting color to maybe help make things a bit more accurate but I don't know if any VHS decks do that.
    This is the advantage that JVC (Victor) claimed with its 629TBC system, which they only advertised in Japan.

    https://forum.videohelp.com/threads/331653-Sr-w5u-auction-alert%21%21%21#post2057782
    https://forum.videohelp.com/threads/379385-Panasonic-Nv-fs200-Ag-1980-Ag-4700-Nv-hs100...st#post2453002
    https://forum.videohelp.com/threads/380454-Panasonic-PV-9451-vs-JVC-SR-V101US?p=246172...=1#post2461721

    The Mitsubishi HV-BS890 I imported has sat unused for years, but in my limited testing, I was never able to discern a visible advantage.
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  21. AJA Kohna LHI S-VIDEO capture attached.

    Those peeping at the histograms will notice the EVAL-ADV7842 having a few little thin spikes. You can see faint bands in the waveform as well. This same artifact appeared on the BlackMagic Decklink Studio 4k (ADV7842). I'd love to capture everything straight with the AJA Kona LHi, but the lack of frame-like TBC means it misses frames, can't capture less ideal/standard signals. Because I can't visually detect those artifacts (please someone point them out, but I can't identify them! looks like it is certain quanta of luma values are over saturated, but not enough for my eye to identify). Because this exists on both the dev board as well as the commercial implementation, I believe it is hardwired in the chip or the implementation was overlooked by me and others.
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    Last edited by petet; 7th Nov 2019 at 20:44.
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    I am curious how you came to the conclusion that the magewell card does not do the 10 bit formats ( P010, P210, Y410 and V410 not counting with additionals formats available only through the SDK) . I have been capturing for about two years at 10 bit 422 lossless and even 10 bit 444 lossless with magicyuv and everything seems normal to me. When you tried the magewell which capture software did you try with it .Do you remember which firmware was installed because in the beginning 3 /4 years ago I did have some levels problems but not recently.Did you tried vhs capture using svideo only , or have you tried also component or even hdmi (through Pana DVD recorder for instance).
    Last edited by FLP437; 7th Nov 2019 at 20:21.
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  23. I am curious how you came to the conclusion that the magewell card does not do the 10 bit formats ( P010, P210, Y410 and V410 not counting with additionals formats available only through the SDK) . I have been capturing for about two years at 10 bit 422 lossless and even 10 bit 444 lossless with magicyuv and everything seems normal to me. When you tried the magewell which capture software did you try with it .Do you remember which firmware was installed because in the beginning 3 /4 years ago I did have some levels problems but not recently.
    Been a long time since I looked at the capture. Also early in my days of what I was looking for in my captures. Swapped about two years ago. I'll edit my first post as it isn't accurate. What I'm seeing is gaps in the histogram - I could have sworn I saw the 9/10 bits empty, but they are quite full now! So it just has issues with having elevated capture levels and these artifacts (attached). Probably related to the level issue. Like it got expanded/stretched and left holes in the luma values.

    EDIT
    Didn't answer your other questions:
    1. I used ffmpeg and virtualdub filtermod / virtualdub 2
    2. I don't remember the firmware version - but latest out in late 2017 / early 2018. (EDIT google says V1.3.0.3825)
    EDIT
    3. S-VIDEO only
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    Last edited by petet; 7th Nov 2019 at 20:32. Reason: Critical reading skills, googling skills, and edit war!
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    I too had in the beginning spiky histograms, meaning there is a levels adjustment going on somewhere. This results in banding even though it is not visible to the naked eye most of the times. I received at the time some tips as have the Proc-Amp at default settings and disable all noise reduction settings if any and others tips I cant remember.I solved the problem not exacly sure how, but I think im my case it was proc-amp related.
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  25. I may have gotten my answer for AGC from the Analog Devices engineers (ADV7842 Register Settings Recommendations 2013):

    It is recommended to select the manual gain option for VCR type signals
    Note: The gain value defined by SDP_Y_GAIN_MAN[12:0] is also used in manual gain mode for non-vcr type signals. However in general the AGC control should be used for standard signals.
    I wonder why... VHS is all over the place and better to just lock it in?
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