DV VHS passthrough device differences?
 

When using a DV device to transfer raw data over firewire, does the device make a difference in the picture/quality of that raw data in the dv file?

For instance, should I expect any difference between sending a VHS tape through a Canon HV40 Camcorder vs a Sony HVR-M35U recorder?

Yes, it compresses the color to 4:1:1 (NTSC) or 4:2:0 (PAL).
- For PAL, it's lossy like DVD-Video.
- For NTSC, it's unacceptably noticeably lossy, to the point where colors get tint shifted (grandma gets a sunburn in Christmas videos, etc).

Most DV devices also lack any TBCs, and will thus bake-in wiggly image errors, dropouts, or audio sync errors.

DV is 1990s technology, and pre-dates 2000s lossless methods still used in the 2020s. In tech terms, it's not just old, but damned old/ancient.

I understand that, I'm specifically asking if the passthrough devices themselves make any difference. Or would video through each device look the same.

He just explained to you that, VHS is analog, there is no such lossless passthrough, The DV device has to convert the analog video to digital then encode it to DV and output it over firewire, The problem is not in the conversion to digital, but rather in the encoding to DV, If you want to just convert VHS to digital without the DV encoding step you will need to use an analog capture device that can spit out digital YUV 4:2:2 into AVI files. Hope this helps.

Seems like I wasn’t being very clear. I’m just inquiring if there is some standard being used here during encoding or if different devices used as a pass through provide different video output when viewing the raw video. Still not clear on that.

Thanks

"passthrough" has two meanings

1. The signal passes through with zero changes. Nothing does this. Everything is always processed in some way. At best, it's passed with minimal changes (and that's NOT a good thing).

2. The signal passes through with use of on-device filters/TBCs/whatever. This is a rare feature, as most passthrough devices "bypass" the features (aka "passed with minimal changes). So, for example, not all DVD recorders have passthrough, only specific models like Panasonic ES10/15.

DV cameras used to "transfer" are outputting compressed DV, period.

So is the compressed video vastly different between 2 different devices? Such as the two mentioned in the OP? Does seem like it’s probably best at this point to just try it and find out.

Thanks for all your help, always appreciated!

For NTSC, yes, noticeably different, even to half-blind grandmas (literally). Color tends to be desaturated, tint shifts, etc. The color is compressed down to 25%. It's harsh.

For PAL, it mostly appears a bit soft, like a DVD-Video on a modern display.

That is a design question, Even though DV devices and camcorders output legal DV AVI, I've seen differences in the way the analog video gets processed, Some are known to produce brighter images with blown out whites, some have darker look, Some have chroma shift, some even have weird artifacts like horizontal lines and color bands, So the short answer to your question is yes, there are differences in those claimed "passthrough" devices. But mostly consumer camcorders, I've seen good images from pro devices and DV boxes, albeit DV compressed.

There are quite a variety of DV hardware encoders I know of:

Standalone Sony DV converters like the Sony DVMC-DA2
MiniDV/Digital8 players with screens - they are probably similar to camcorders, but can't say for sure.
Canopus products like the ADVC100/110
MiniDV/D8 camera encoding via line in - a few brands can likely do that such as Sony, Sharp, Canon, Panasonic
Datavideo standalone DV capture devices that have analog inputs.
Professional DV playback decks - I've seen these from panasonic, JVC, and Sony - I'm sure there are others.


As for which is best, I've never seen much of a direct comparison to show if one is any better than the others. What you'd be looking for is color accuracy and if they like to clip high or low values. The Canopus can be set to not clip at low IRE levels by setting the black level to 0IRE instead of the usual 7.5 for NTSC. I haven't seen more than maybe two devices compared together at once which isn't going to tell you a whole lot as to which is "best".

Ahh, thank you! This answers my question. I meant to give this a shot last night between a few devices I have but of course, can't find a power cable for one.

Thank you! For now, I'm sending video through a Sony DV device from a AG-1960(I know, no tbc) and the color slider has been very helpful in at least toning down the apparent heightened reds/purples.