An attempt to obtain video and audio files from tape backup

[WildcatMatt]

I have some backup tapes which should contain WAV audio and MJPEG video that was created on the Panasonic Postbox nonlinear editing suite back in the late '90s. I'm curious to see whether it's possible to extract the original files and play them back for historical/archive purposes.

Using an OpenSUSE Linux system and dd I was able to read back files from the tape. But when I look at the files, I don't see any expected header data, although there's definitely a regular pattern to the start of the files. If I try opening them in VLC it seems to think they're media files but it doesn't play anything back.

It's possible the files are compressed or encoded in some fashion, or I used incorrect settings when I read the files in.

I've attached a dump of the first 30 files on the tape in the hopes that someone may recognize the patterns or have other ideas about what steps I could try.

Thanks!

[jagabo]

file00004 contains raw audio data. Big band jazz. I imported into Audacity as raw 16 bit stereo data. It ends abruptly so maybe another file needs to be appended. There's some hope some of the other files can be restored. WAV files attached. I didn't remove the archive header from the start of the file so there's a click at the start. It looks like there's 512 bytes of header data at the start of each file. But it doesn't seem to contain the filename or other identifiable information. Maybe there's an index file somewhere?

[Cornucopia]

Using history as a guide, this box, which was a Win95-era IBM machine, would have not used any of the more modern container file formats - mp4, mkv/webm, mxf, aaf, wmv, or flv even.
No, the formats that were available at the time (not counting realmedia or swf, which were NEVER used as intermediate/production formats) would be: mov, avi, omf, mpeg1-ss, mpeg2-ps, mpeg2-ts. Or raw/elementary streams. My guess is the last.

Try one of the large files and mux it into avi using standard ntsc sd parameters. Maybe it will play then.

Scott

[amaipaipai]

What a piece of history, there is a guy rehearsing TV spots or radio commercials. Is that you on the microphone?
According to this site, this are the specs for audio and video, and looks like it was MJPEG after all.

Video Performance
S/N Ratio*:  55dB (Y/PB/PR), 53dB (Y/C), 50dB (Composite)
Crosstalk*:  50dB=3.58MHz
DG, DP*:     3%, 3¡
Frequency Response*: 4.5MHz, +0dB, -3dB
Sampling Frequency:  13.5MHz, 4:1:1, 8 bit component
Y/C Separation:      3 lines, digital logical comb filter
SC-H:        ±30¡
Compression: MOTION JPEG (CCIR-601 compatible)
Video Quality:       Level Q6, Q8, Q11, Q23
Recording Time:      Approx. 6 min/GB (Q6)
     Approx. 8 min/GB (Q8)
     Approx. 11 min/GB (Q11)
     Approx. 23 min/GB (Q23)
Title Graphics:      Resolution: 640x480 dots Y, U, V, 8 bit component each
     Font: True type

Audio Performance
S/N Ratio:   More than 70dB (1kHz, XLR OUT)
Dynamic Range:       More than 88dB
Total Harmonic Distortion:   0.05% (1kHz)
Frequency Response:  20kHz, +0, -3dB, 20Hz, +0, -3dB
Sampling Frequency:  48kHz, 16 bit
Mixing:      Stereo 4 channels
Effector:    EQ, Reverberation
Recording Time:      Approx. 86min/GB

Knowing what codec we are dealing with, maybe is possible to construct a filter with Graphedit using any MJPEG decoder to convert to another video format.
https://betweeneyebrows.wordpress.com/2016/07/25/directshow-on-windows-10-missing-graphedit/
https://www.videohelp.com/software/GraphEdit

I get no good returns from ffmpeg maybe because of the file header.

[Cornucopia]

Unfortunately, there are a number of flavors of mjpeg, so it may be more work than that.

Scott

[WildcatMatt]

Thanks for the fantastic replies so far. I wrote a script to chop 512 bytes from each file and then run it through sox which seems to have recovered the vast majority of the audio files -- one or two seem to have nonstandard settings compared to the rest but that'll just be fiddling with settings.

It's not my voice on the tracks, but now that I can hear the audio files this tape appears to have assets for TV promotional spots.

I'll try to do some playing with the larger files that I expect to be video and see what happens.

[jagabo]

If you can't restore your video files upload one and I'll take a look at it. Note that AVI and WAV files start with the four letters RIFF. So they should be easy to identify. Many other AV containers have similar identifying patterns at the start.

[WildcatMatt]

If you can't restore your video files upload one and I'll take a look at it. Note that AVI and WAV files start with the four letters RIFF. So they should be easy to identify. Many other AV containers have similar identifying patterns at the start.

Here's a single file from the tape which I suspect is a video file. Given that the audio files are RAW, I wouldn't be surprised if the video files aren't in a proper container either.