Dumb hypothetical question about LSI DVD recorders (e.g. JVC DR-MH300))

[servese43]

I'm feeling stupid just writing this, but would it be possible to mod an LSI-based JVC/Toshiba recorder so that it outputs/records lossless video of some description? (Either to the hard drive of recorders that have one or over a bus like USB or firewire.) The idea being that you get the benefit of a capture device that handles tapes well and has high-quality filtering without having to capture to a lossy codec. How would a hypothetical modded DVD recorder compare to capture cards from the ATI AIW range or the ATI 600 USB?

[lollo2]

I don't know about JVC DVD recorders A/D circuitry quality (if they are using LSI chip is great for sure, I worked in the past with LSI design engineers!), but you have several examples in this and other forums about the results of capturing using some Panasonic DVD A/D circuitery for digitizing analog videos with the flow S-VHS VCR with/without line TBC -> Panasonic DVD -> lossless HDMI -> HDMI capture.

To my understanding (and limited experiments with borrowed hardware) the quality of the A/D video conversion is slightly inferior or equivalent to what can be achieved with the best capture cards (ATI AIW, Canopus NX, few USB cards) using a standard flow S-VHS VCR with line TBC -> capture card.

However, the first has the advantage that for problematic tapes the jitter correction of the Panasonic DVD may fix some problem without adding an ES-10/15 or similar compared to the "standard" flow, that would cause an additional A/D conversion with consequent small loss of quality.

In both chains a frameTBC could be needed, but that's another story.

User Bogilein for sure has more data and could report video comparison about this topic

[hodgey]

You can grab the hdmi (or analog outputs) from it, everything goes through the A/D chips in them like in every dvd-recorder. As far as I know the noise reduction and what not in the LSI is part of the encoding process so for that you have to actually record. The MH300 and maybe some others can also record in DV format to the hard drive. I haven't tested much myself but I don't remember the DV recording looking like it had any extra denoising or processing.

The LSI DoMiNo chips don't do the analog-digital conversion part (or at least not on any schematic I've seen.) It's paired with some other A/D chip which varies between devices. Many use Texas Instruments chips like TVP5146 and similar, or NXP/Philips SAA7136 and similar. The JVC ones has some custom JVC branded chip (labelled JCP8059 in the datasheets.) The panasonic ones may use a Panasonic one but not sure (I've also seen images from one combo one that just had a TVP5150 though so it may vary). A store-brand one I got has a LSI-labelled A/D chip but from what I could find it's likely just a rebranded Ti one.

From the ones I have used, the MH300 seems to have a somewhat limited line-tbc function (that can't handle larger tearing issues like panasonic and NEC-based ones do.) but is quite prone to frame drops, I didn't notice any noise reduction or other processing. My LG RH188H (SAA7136 A/D chip) doesn't do anything special either, it seems somewhat solid at locking to bad video maybe courtesy of the Phlips/NXP A/D chip though it doesn't correct horizontal jitter any more than say the cypress TBC units. (I think my LG VCR/DVD combo recorder was pretty similar but haven't tested that one much.) The last LSI based-one I have is a store-branded/generic one ("Advent"), using a "LSI L2146" (likely a rebranded Ti TVP5146), seemed to lose sync easily with bad video and didn't see any other effects here either.

[lordsmurf]

The chroma NR is part of the LSI DMN chip. And the MPEG encoding happens on the chip. I have detailed schematic on it, somewhere, from when I did recorder review from about '02 to '11. It's encode+NR, not the raw basic A>D, which is why the quality varies model to model, recorder to recorder, on LSI-based decks.

Mod the recorder? No, doubtful.

But in theory, yes, it's very possible to extract the LSI chipset (maybe some others from the board), and homebrew design a card around it. In fact, Creative did it, but that card failed for many reasons (horrible drivers, OS locked to pre-XP, etc).

You could even make it better, by tweaking the IRE correctly, instead of having typical luma/IRE offsets like all DVD recorders tend to do. I'm not entirely sure where luma/IRE failings are, but the chip does have some contrrol over that, and it seems to be tweaked for PAL, and not tweaked to NTSC.

LSI is a brand, don't lump all LSI chips together. For the JVC-type (Apex, LiteOn, etc) LSI-based recorders, we're specifically referring to the DoMiNo chipsets.

If anybody can build such a card, contact me.

[servese43]

Thanks everyone for all the detailed replies and interesting info about these DVD recorders. The filtering being tied to MPEG-2 encoding explains why I haven't seen any suggestions of using a DoMiNo-based DVD recorder as a budget passthrough filtering device.

I found a thread about the card lordsmurf was referring to:

http://www.digitalfaq.com/forum/vide...-zs-video.html

Definitely sounds pretty useless, especially considering that it's only able to record in MPEG-2, negating the one possible benefit the card might have been able to provide.

Would it be possible to "hack" the firmware of one of these DoMiNo-based recorders to add an option to record MPEG-2 at a very high bitrate like 50Mb/s, so that you get an almost lossless recording? (ala some of the Sony DVD recorders like the RDR-HXD870)