Issue with NTSC speed

[LiudasP]

Hi,

I'm digitizing a few tapes recorded with Hitachi VM3100A Camcorder (NTSC). JVC HR-D830U (pure NTSC) is playing them now, since I no longer have the camera.
Some of tapes are easy, but when encountering some episodes, the recorder starts to play the tape faster (internal buzz in VCR changes too) and picture becomes black with some white stripes.
Audio on phones can be heard, but with higher pitch. Capture software (VirtualDub) shows the signal as 29.97fps. If I rewind to some previous episode, picture and sound are correct, VCR runs on "normal" speed.
As soon as specific episode starts - the same story with everything running faster. Some other tapes start faster immediately, but everything becomes normal again as soon as another tape is inserted on "good" episode.
So I don't think VCR unit needs repair. When switching the VCR to EP - playback and audio is too slow, the same black picture with flickering white stripes. FF with picture displays some recognizable video.
I took Sony SLV-ED4 (PAL unit, capable of NTSC playback) and started digitizing at "good" episode and to my surprise it continued to output picture and sound,
albeit again running somewhat faster. The whole capture was done at 29.97fps with first "good" episode running at normal speed, but the next running faster.
When I change the frame rate in resulting AVI file to 23.976 - picture runs at right speed, but audio is too fast. If I apply speed multiplier of 0.8 to audio in Audacity - audio speed is right.
What is necessary in order to capture everything correctly? VCR with LP? Since my JVC seems to be capable of SP/EP only. And it is possible some episodes were recorded at different speeds.
I could acquire some better VCR with TBC, but first would like to know what is missing here and which device would help for sure. My another Panasonic NV-HS820 (sVHS PAL) shows all the tapes and episodes, but it outputs the PAL60 and I would prefer native format when possible.

regards,
Liudas

[ProWo]

You could capture the problematic tapes twice, once at 29.97 fps and once at 23.976 fps.
Then you should have a correct variant of each episode, which you can cut individually.

[LiudasP]

Possibly. How do I tell my VCR to run on 23.976 fps and not change speeds? Which VCR can do that? Or is it just LP mode?

[ProWo]

How do I tell my VCR to run on 23.976 fps and not change speeds?

Not the VCR, the capture device.

[LiudasP]

Tried it. The same white lines on black screen at whatever rate, be it 5, 10, ... 60 fps. Blue VCR menu can be captured at all these rates no problem. FF with picture shows some video as usual while cueing, but it all becomes white lines as soon as tape speed settles down - the similar lines as while cueing. Picture becomes for a moment better when tape speed is slowing after FF release. I view on PC screen, no TV attached.

[Cornucopia]

The 23.976 option is a red herring. Unless I'm very mistaken or out-of-date, ALL standard consumer capture devices for video will capture at PAL (25/50) or NTSC (29.97/59.94, or possibly 30/60) rates. Only pro devices natively capture at 23.976/24. All the others capture at 29.97 and convert to 23.976 on the fly when saving. Not a great combination, as you usually cannot control its operation/algorithm. ProWo's idea could very well drop frames.

Also, 29.97 <--> 23.976 has no change to duration, nor "speed" especially WRT audio.

Sounds to me like your VCR only plays SP or SLP/EP, and doesn't accept LP. And betting the tape is recorded alternately in SP and LP. Will need a diff VCR.
Simple as that. Make sure you get one where you can adjust the tracking - you'll likely need it.

Scott

[ProWo]

Hi,
I took Sony SLV-ED4 (PAL unit, capable of NTSC playback) and started digitizing at "good" episode and to my surprise it continued to output picture and sound,
albeit again running somewhat faster. The whole capture was done at 29.97fps with first "good" episode running at normal speed, but the next running faster.
When I change the frame rate in resulting AVI file to 23.976 - picture runs at right speed, but audio is too fast. If I apply speed multiplier of 0.8 to audio in Audacity - audio speed is right.

You can cut out the episodes that are to fast and re-encode video track and audio track separately, 29.97 fps -> 23.976 fps, video lenght corrected, audio lenght and pitch corrected.
Then mux the two tracks together.
You can do this with clever FFMpeg-GUI
https://forum.videohelp.com/threads/396490-clever-FFmpeg-GUI-a-new-small-GUI-for-FFmpeg