[mythtvnz] OT: recording from VHS

[Stephen Worthington]

On Sat, 18 Jul 2009 19:45:04 +1200, you wrote:

>On Sat, 2009-07-18 at 19:22 +1200, Tortise wrote:
>> The best recording format may be H264 - at either 576i or possibly even de-interlaced to 576p but maybe no advantage in 576p as the 
>> de-interlace would do its stuff on playback in any event.?  (Reason - smaller files)
>> I am not sure how we'd do that in H264 though and the kit would need to be up to SD H264.
>> Has anyone tried this?
>> 
>> ----- Original Message ----- 
>> From: "Criggie" <criggie at criggie.dyndns.org>
>> To: "MythTV in NZ" <mythtvnz at lists.linuxnut.co.nz>
>> Sent: Saturday, July 18, 2009 6:45 PM
>> Subject: Re: [mythtvnz] OT: recording from VHS
>> 
>> 
>> Jim Cheetham wrote:
>> > I'd like to increase the utility value of a stack of VHS cassette
>> > tapes I have here, by digitising them so they can be played back by
>> > Myth. I still have a working VHS player (with RF and RCA outputs).
>> > What hardware would be good to get that would help me record from the
>> > player? I only have DVB-S cards at the moment ...
>> 
>> Video tapes are standard definition, so anything "high def" would be a waste.
>> 
>> I use an old nicam recorder plugged into the RCA composite input of one of
>> my PVR150 (the other one doesn't have these physical sockets)
>> 
>> However the quality isn't great, and of course you can only watch at 1
>> speed :)
>> 
>> 
>> Others have recommended cat /dev/video0 > file.mpg
>> but I run up mythfrontend and record closer to the desired position by
>> simply pressing R while watching.  Be aware that the tape is running
>> anything from 2-5 seconds ahead of what you see and hear on screen though.
>> 
>> Then once the recording is done, you can edit the cutlist and transcode
>> out adverts or any lead in/out.
>
>Try to stick with the quoting style, it's hard to follow the
>conversation when it jumps all over the place.
>
>Any framegrabber card/device can do H264 if the host hardware is up to
>it.
>
>hads

Not really.  There are very few CPUs that might be able to encode to
H.264 on the fly.  It is very CPU intensive.  And for the best results
you normally want to do 2 pass encoding anyway, which is impossible on
the fly.  One pass fixed bit rate encoding gives pretty bad results,
and that is the only method that you have any hope of doing on a
normal CPU without dropping frames.  One pass quanitzer encoding
(fixed quality, variable bit rate) can give good results if you have
enough CPU, but 2 pass encoding will still be a little better.

The best results from tape capture are by capturing the raw video
signal directly to hard disk (usually an AVI file).  This takes around
1.2 Gibytes of disk per minute of video.  You can reduce that to
around 1 Gibyte per minute by using a lossless compression codec such
as HuffyYUV.  Then once the capture is done, you use the normal tools
to do a proper 2 pass encoding to H.264.  That will happen at well
less than the frame rate of the capture - IIRC, my system can do about
5 frames per second on the second pass of an H.264 encoding, at "best"
encoding settings.  So encoding a 90 minute VHS tape takes several
hours - just leave your PC doing it overnight.

If you have something like a PVR150 that does hardware compression to
MPEG-2, and you capture that and then convert to, say, H.264, you are
doing two compressions, and you lose quality by doing that.  So you
are still better off using the PVR150 to capture to a raw AVI file and
then do just one compression from that.  I have not tried it with my
PVR500, but most cards with builtin compression can also do raw
capture.

Of course, all of the above assumes that your VHS tapes are good
quality.  If they are not, then the hardware compression to MPEG-2
will likely not produce a result that is much different from playing
the tape.  And it is *much* easier to do.

Also, if you have access to an S-VHS video, that is a better tool for
capturing old tapes.  S-Video has much wider bandwidth and the S-VHS
videos were normally built to high quality standards compared to most
VHS videos.  So you get to see all the signal that is actually on your
tape, rather than have its quality reduced passing through the VHS
video.