[FFmpeg-user] Does "cat" degrade video quality?

[Dan Harkless]

On 12/2/2022 11:17 AM, MyCraigs List via ffmpeg-user wrote:
>   Dan,
> Thanks for the reply.  They are family videos some of which were made with a (I think) "tape eating" Panasonic and then later a Sony mini-DV tape video camera(s).  Now I use a Sony video camera that records in MTS to an sd chip.  I think the tape cameras produced AVI files (I think...but am not sure).  I still have the tapes but can't/won't transfer them from the camera for fear of destroying them (tape eater camera....both).

Understood.  I had a Sony MiniDV camera that started getting bad audio 
dropouts.  At the Sony service center (back in the good old days when 
there was a local one), I learned that the cause was my mixing different 
brands of MiniDV tapes.  Apparently the different lubricants the 
different brands use react together to produce a sticky residue.  It was 
reportedly OK to use, say, Panasonic tapes with a Sony cam, but only if 
you *always* used Panasonic tapes. After I got my camera back from the 
service center, I only used Sony tapes from then on.  Not that that 
necessarily has anything to do with your tape-eating problem, which is 
probably issues with the transport mechanism, but I thought I'd mention 
it since you said you had Sony and Panasonic cameras.

And yeah, the Sony capture application produced AVI files with DV contents.

> The VOB files are from DVD's I made from the tape cameras.  It's the best I've got without the aforementioned problems.  I don't expect much super quality out of them but they're good enough.  Would it be smart of convert them to a format such at mp4 and H.264....for preservation of a common standard?
> As to the MTS files- the quality is excellent.  Cat does a great job and I'm amazed how a clod such as myself got perfect results.  But....but....perhaps it also would be smart to convert them to mp4 H.264?

I don't think MPEG-2 compatibility will be going away any time in the 
forseeable future, especially since the later formats like H.264/AVC and 
H.265/HEVC are also MPEG standards.  MPEG-2 videos have slightly better 
picture quality than they do after transcoding to AVC or HEVC, so the 
only reason to convert to one of those formats would be to save disk 
space.  If you have enough space to keep them in MPEG-2 format, I would 
do that.  MPEG-2 is also easier for video editing programs to deal with 
than the later, more highly compressed standards (especially if you want 
to make frame-accurate edits), though not as easy as DV format (the one 
used on the MiniDV tapes themselves), since *it* only uses intraframe 
compression, not interframe compression.

> I'm pretty old and want our kids to be able to watch these videos in the future when I probably will have broken the social security system.
> Thanks....will look link below.
> Thank you, again...
> Craig

I don't have a suggestion for the MTS files (beyond using ffmpeg to 
concatenate, if cat results in problems at the concatenation points), as 
my cameras don't produce that format, but if I were you, I would 
download MakeMKV:

     https://www.makemkv.com/

which is available for Windows, Mac, and Linux.  Rather than trying to 
mess with VOB files directly, you can use that application to convert 
each DVD to a series of .MKV files (one per "title" on the DVD; you may 
or may not have more than one, depending on how you authored them), with 
MPEG-2 contents.  The nice thing about doing it this way is that there 
is zero loss of quality, unlike with apps that go directly to AVC or 
HEVC.  Also, you don't have to make the decision of whether to 
deinterlace to ~30 frames per second or line-double the fields to ~60 
frames per second (assuming you're in NTSC land) — you can leave the 
MPEG-2 interlaced, and let the player deal with it (not a problem for 
modern programs like VLC).

MakeMKV is in a semi-permanent Beta state, so you need to periodically 
download new license keys from:

     https://forum.makemkv.com/forum/viewtopic.php?t=1053

but aside from that, it's easy to use, and is free and open-source. Good 
luck with your family video preservation, and cheers.

--
Dan Harkless
http://harkless.org/dan/