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happycube / ld-decode

Software defined LaserDisc decoder
GNU General Public License v3.0
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Metadata considerations for tape support #750

Open simoninns opened 2 years ago

simoninns commented 2 years ago

Lots of discussion on discord about the possibilities of expanding metadata support for tapes. It's likely that, in the first case, it will simply be considered a 'format' and placed with CAV/CLV to distinguish tape from LaserDiscs. However, there were some good notes about the complexities; so this issue is to keep them in case needed:

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Stephen_Neal: Timecode in tape is interesting - as it's not really mandated by the tape format, it's more a choice. Linear Timecode is carried on audio tracks, Vertical Interval Timecode (aka VITC) is embedded in the VBI of the video signal. Both are standardised. There are some oddball VHS indexing systems that use custom modulation of the CTRL track - but they are quite niche and are more indexing rather than timecode standards.

[12:43] Stephen_Neal: So you could have VITC or LTC on VHS, S-VHS, Hi8, UMatic - or both. (VITC gives you timecode when you have pictures, LTC gives you timecode when the tape is moving)

I think it could be categorized (imo) by: - Media type: optical (disk), magnetic (tape) - Media format: LD, CRV, CED, VHD, VHS, S-VHS, W-VHS, Vi8, Hi8, U-Matic (LB/HB/SP), Betacam, Betamax - Recording speed: CAV, CLV, EP, LP, SP, B1, B2, B3 - Timecode type: VBI (VITC), CTL (LTC) - Audio type: Digital (PCM/AC3), Analog Helical Stereo (HiFi), Analog Mono, Analog Stereo. - Color system: (ME)SECAM, PAL, NTSC, D-MAC - Color format: color-under, composite, component - Line system: 525, 625, 1135, 1250 etc. - Scan type: Interlaced (fields), Progressive (frames) - Refresh rate: 50Hz, 59.94Hz, 60Hz Stephen_Neal: I think CTL and LTC are two different types - most VCRs that used LTC for timecode will also have had a separate CTL track (not sure about Video8/Hi8) [14:08] Stephen_Neal: I'd also avoid mono vs stereo and instead include a track count and track type format - so you can cope with 3 x Linear tracks, 2 x FM + 1 x Linear, 2 x FM + 2 x Linear, 2 x FM + 2 x PCM etc.? [14:10] Stephen_Neal: It depends whether the metadata needs to carry 'how many audio tracks' (Dual Mono and Stereo would both = 2) or 'how many audio tracks AND what they are used for' (Dual Mono and Stereo would have different metadata). It then gets complex
harrypm commented 2 years ago

Note Discord Message Chain

Copying over my note about the Sony Video8 and High8 formats having Sony's RCTC (Rewritable Consumer Timecode) that's in the main RF signal alongside audio/video I believe, making it possibly the easiest one RF capture needed tape format in terms of the consumer formats.