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Draft:.TBC Time Base Corrected Format

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The .TBC format created by Chad Page, is a free to use and open source developed video signal file formatting standard for uncompressed decoded analog video signals after software time base correction.

This format was originally developed and used for the Domesday86[1] LaserDisc Recovery Project[2] preserving the 1986 BBC LaserDiscs original modulated video/audio/data signals directly off the laser reading the pits of the disc.

Time Base Corrected (.tbc)
ld-analyse icon 2023 (Linux/Windows/MacOS)
Filename extension
.tbc & _chroma.tbc
Developed byChad Page*
Initial release2018
Type of formatUncompressed Video
Container for16-bit greyscale (GREY16)
Standard4fsc NTSC/PAL
Open format?Yes
Free format?Open-Source
Websitehttps://github.com/happycube/ld-decode/wiki/JSON-metadata-format

Related is the open source hardware DomesDayDuplicator[3] (DdD) a USB 3.0 40msps RF capture device, standerdised by the projects for capturing orignal modulated RF signals off laser-discs but is compatable with analouge tape formats, but not composite video directly.

Software Time Base Corrected File

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Y+C (Luma + Chroma) Chroma, VHS-C SP (SAR 1:1)

The format is a lossless and headerless, 4fsc sampled digital file format not dissembler to D-2 & D-3 video tape, storing time base corrected composite/s-video (combined or luminance/chrominance separated) analogue video signals in 16-bit unsigned grey scale "GREY16" values allowing signals to be stored and processed on affordable mass storage HDD/SSD drives or archived to optical discs such as M-Disc or Sony ODA and standard LTO data tapes.

These can be inspected inside the open source tool ld-analyse for frame by frame signal analysis on Windows, Linux & MacOS then files can easily be encoded to a video file via FFmpeg typically to a lossless interlaced FFV1 10-bit 4:2:2 file using the .mkv container then de-interlaced via W3FDIF[4] or more modern de-interlacers like Avisynths QTGMC[5] and IVTC for 24p or film content.

Media sources like LaserDisc and Composite (CVBS) are stored in one single TBC file and color-under tape formats such as (S)VHS, BetaMax, Umatic, Umatic-SP, Video8, High8, Video2000, Philips VCR, Philips N1500, Philips N1700 have luminance/chrominance separated into two TBC files allowing for cleaner direct image processing for black and white but especially color images, notably the chroma is QAM modulated as such this is playback compatible with standard S-Video output.

Formats like Betacam & Betacam SP, are still in development stage (FM Demodulation filters) but will be later supported by the system like the EIJ-1, EIJ-2, 1" Type-C formats..

History & Current Day Usage

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While originally developed for LD-Decode[6] due to being open source, it has subsequently gained wide usage and development expansion by the VHS-Decode[7] (FM Modulated tape decoding, not limited to just VHS) & CVBS-Decode[8] (composite video decoding) projects, under the domesday86 community creating a modern archival ecosystem, consisting of directly digitizing the original modulated or even baseband composite signals off analogue mediums to be preserved and de-modulated later, skipping the immediate and optional processing of dedicated internal and or external hardware entirely removing the need for physical time base correctors commonly required for reliable standard capture.

Use In Lossless Analogue Playback

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As the format allows for composite/s-video streams to be stored with sync signals (sub-carrer locked or line-locked), the files contents be streamed directly to an Digital to Analogue Converter (DAC) for live real time playback to an CRT or equipment with analouge inputs currently this is achieved with low cost USB 2.0/3.0 VGA adaptors that use the Frisco Logic 2000 (FL2K) chipset and a modified driver for Windows & Linux publically available on GitHub[9].

VHS SP - Full Signal Frame SMPTE Colour Bars Decoded in 2021 - VHS-Decode Note: Image brightness levels may not be displayed correctly on your computer display.

Format Description

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General Information

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  • Format Name: ''TBC'' Time Base Corrected
  • Year introduced: 2018
  • Developer: Chad Page (Primary Developer)
  • Format Type: 4fsc Composite or Y/C
LD-Analyse Vectorscope

Primary Data

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  • TV System: PAL/PAL-M/NTSC/NTSC-J/SECAM/MESECAM
  • Data Format: 16-bit unsigned grey scale
  • Image Area: Full VBI/Active/Sync
  • Format type: digital composite & digital s-video
  • Resolution PAL: 1135x625
  • Resolution NTSC: 910x525
  • Sampling Rate: 4fsc PAL (17727262 Hz)
  • Sampling NTSC: 4fsc NTSC (14118181 Hz)
  • Data Rate PAL:
  • CVBS 2.1GB/min 35MB/s (280mbps)
  • Y+C 4.2GB/min 70MB/s (560mbps)
  • Data Rate NTSC:
  • CVBS 3.4GB/min 56.66MB/s (453mbps)
  • Y+C 1.7GB/min 28.33MB/s (226.5mbps)

Metadata[10]

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  • Format: .JSON (file is metadata for the single or pair of TBC files)
  • Information Type: Frame Descriptor Table
  • Information Content: System NTSC/PAL, Frame Count, Signal Dropouts, Black Signal To Noise Ratio, White Signal To Noise Ratio, Closed Captioning, VITS Signals, VITC Timecode.

Audio

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  • Codec: PCM Uncompressed & FLAC Lossless Compressed
  • File Extension: .WAV or .FLAC
  • Bit depth: 24-bit Integer or 32-bit Float
  • Sample Rate: 48khz ~ 192khz
LD-Analyse With Scan-line Ossiliscope

File System Layout

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Direct CVBS

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  • filename.tbc - CVBS Image Data
  • filename.tbc.json - Frame Descriptor Table
  • filename.wav - External Audio

LaserDisc

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  • filename.tbc - CVBS Image Data
  • filename.efm - Digital audio/data track
  • filename.pcm - Uncompressed 44.1Khz 16-bit stereo analogue sound track
  • filename.log - Date Indexed Action & Decoding Output Log

Tape Media

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  • filename.tbc - Luminance Image Data
  • filename_chroma.tbc - Chrominance Image Data
  • filename.tbc.json - Frame Descriptor Table
  • filename.log - Date Indexed Action & Decoding Output Log
  • filename.wav - Linear Audio (Mono/Stereo or LTC timecode)
  • filename.flac - HiFi Decoded Stereo

TBC File Processing Suite

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Linux & Windows supported, ld-tools is a set of tools to handle and process TBC files.

  • ld-process-vbi - Reads VBI Data such as time codes, closed captioning, CGMS-A saving its traslated value into the .JSON metadata file.
  • ld-process-vits - Reads VITC test signals and saves updated Black & White SNR values into the .JSON metadata file.
  • ld-process-efm - LaserDisc Only, processes digital audio data.
  • ld-export-metadata - Exports .JSON metadata to stardard formats for external use.
  • ld-chroma-decoder - Decodes the QAM modualted chroma signal for muxing to normal colour video .
  • ld-chroma-encoder - Encoder that takes raw video and encodes it to the TBC format in CVBS or S-Video.
  • ld-disc-stacker - Image frame stacking for the .TBC files.
  • ld-dropout-correct does dropout correction on a single TBC file or stacks data from multiple files to composite a cleaner file.

Tools Exclusive to use with the DomesDayDuplicator:

  • ld-lds-converter - Converts 10-Bit packed captures to 16-bit signed used to unpack to file or in realtime for ld-compress
  • ld-ldf-cut - allows for cutting of RF data files
  • ld-compress - Compresses 10-bit/16-bit FM RF data into a FLAC file saving 30~60% space.

Related Tools:

  • tbc-video-export - (Linux/Windows/MacOS) Exports video files from single or tbc file pairs, and runs ld-dropout-correct/ld-process-vbi and ld-chroma-encoder with FFmpeg to make a final video file. (.py & .exe tool)
  • gen_chroma_vid.sh - (Linux/MacOS) Exports a FFV1 4:2:2 10-bit video file, first script made for duel tbc file export. (.sh script)

LD-Analyse (TBC Analysis & Adjustment Tool)

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Black Signal to Noise Ratio Graph
LD-Analyse Dropout Loss Analysis Graphing Output
  • Y+C (Luma + Chroma) Chroma, VHS-C SP
    Y+C (Luma + Chroma) Chroma, VHS-C SP
  • Y (Luma) Source Mode, VHS-C SP
    Y (Luma) Source Mode, VHS-C SP
  • Y (Chroma) Source, VHS-C SP
    Y (Chroma) Source, VHS-C SP
  • C (Chroma) Source Mode, VHS-C SP
    C (Chroma) Source Mode, VHS-C SP
  • LD-Analyse Vector Scope
    LD-Analyse Vector Scope
  • LD-Analyse Chroma Decoder Control PAL
    LD-Analyse Chroma Decoder Control PAL
  • LD-Analyse Chroma Decoder Control NTSC
    LD-Analyse Chroma Decoder Control NTSC

LD-Analyse the primary application for viewing the TBC files directly allows for frame by frame inspection of the whole active image area and vertical blanking area, simmer to a H/V shift capable broadcast CRT's (Sony PVM/BVM etc) the whole signal area is available, and aspect ratios such as 1:1 SAR, DAR 4:3 & 16:9 can be defined, with dropouts being visually displayed with an overlay using red/blue colours on the effected lines of analogue video.

As shown with the set of images above and to the right side there is visual information and its relating graphing data of white and black signal to noise ratio and dropouts can be also viewed, there is also a vector-scope and scan-line oscilloscope Chroma colour decoding and video levels data can be changed on the fly inside ld-analyse to then be adjusted on the single command encoding to a final video file.

LD-Analyse ability's

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  • Vector-Scope
  • Scan-Line Oscilloscope
  • Visual Dropout Display
  • FTT Visulisation Overlay
  • Black & White Video Level Adjustment
  • PNG Image Export

References

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  1. ^ "Domesday86.com". Domesday86.com. Retrieved 2023-03-13.
  2. ^ "Domesday86 Laser Disk Preservation". Domesday86.com. Retrieved 2022-11-21.
  3. ^ Munday, Harry (2022-10-11), Domesday Duplicator (With Docs Version), retrieved 2022-11-21
  4. ^ "w3fdif - FFmpeg". underpop.online.fr. Retrieved 2022-11-30.
  5. ^ "QTGMC - Avisynth wiki". avisynth.nl. Retrieved 2022-11-30.
  6. ^ "Home · happycube/ld-decode Wiki". GitHub. Retrieved 2022-11-21.
  7. ^ oyvindln (2022-11-24), VHS-Decode (It does more than VHS now!), retrieved 2022-11-24
  8. ^ "CVBS Composite Decode · oyvindln/vhs-decode Wiki". GitHub. Retrieved 2022-11-24.
  9. ^ vrunk11 (2022-10-25), FL2K TBC Player, retrieved 2022-11-21{{citation}}: CS1 maint: numeric names: authors list (link)
  10. ^ "JSON Metadata format · happycube/ld-decode Wiki". GitHub. Retrieved 2022-11-21.
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Source (GitHub) References
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Technical References
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