File & Data Formats

RF Capture Formats

CXADC 16-bit Unsigned

CXADC 08-bit Unsigned

DdD 10-bit Packed (10-bit unsigned integers)

DdD 16-bit Signed

Context of Extension Formats

.lds - DDD 10-bit Packed or 16-bit Signed 40msps

.ldf - FLAC Compressed 16-bit 40msps (DomesDayDuplicator)

.cds - 10-bit Packed 10msps (4:1 decimation mode)

.s16 - Uncompressed Signed 16-bit (40msps DomesDayDuplicator)

.u8/.r8 - CXADC 08-bit Unsigned

.u16.r16 - CXADC 16-bit Unsigned

.vhs - FLAC Compressed VHS 8-bit or 16-bit

.svhs - FLAC Compressed S-VHS 8-bit or 16-bit

.cvbs - FLAC Compressed CVBS 8-bit or 16-bit

.flac/.wav/.raw can also be used but would need file name context.

The decoder accepts RF data in 10-bit packed 8-bit raw and 16-bit raw sample formats and FLAC compressed bit depth is automatic.

Decoder sample rate is 40msps by default, anything different has to be manually defined via -f 20/-f 16 for 20/16msps for example.

Archives have been standardised to 40msps 8/10/16 bit & 20msps / 16msps 8-bit compressed in FLAC.

TBC Data Output Formats

filename.tbc - Luminance Image Data (Full Composite if cvbs-decode/ld-decode)

filename_chroma.tbc - Chrominance Image Data

filename.tbc.json - Frame Descriptor Table (Resolution/Dropouts/SNR/Frames/VITC Timecode/Closed Captions)

filename.log - Timecode Indexed Action/Output Log

The TBC Format

TBC Acronym, Time Base Corrected .TBC is a lossless digital file format containing time base corrected digitized composite signal.

A TBC retimes a video signal to make video lines (like a shredded piece of paper) more accurately the same length when displayed i.e correcting the time base of each line/field this fixes wobbly or skuied images as observed on lower-quaility and or out of calibration VCRs the lines vary in length across the picture.

The software decoders are not a frame store so what you get is what you get, fully dropped frames of signal data just don't exist.

In a stable tape workflow a TBC acts as a buffer and conforms signal output to a stable legal output, that's acceptable for use with broadcast equipment and do dropout correction based off RF signal level drops.

Drop out detection is done during decoding, however it does gather data for doing that afterwards with the chroma-decoder and is enabled by default.

The time base corrected file or files are created directly after the signal de-modulation & filtering.

Decoding takes the 2 channels chrominance and luminance (C & Y) and creates separate TBC files for each respectively this allows for very clinical post adjustments and the ability to remove Croma entirely if unstable and or source is black and white media for example.

Originally developed for LD-Decode, the TBC format contains the full time base corrected 4fsc video signal in the digital component space using standard 16-bit unsigned greyscale values or GREY16, however the chrominance (colour data) and luminance (image data) are separated for tape decoding as these are seprated signals on the [colour-under-tape formats] this allows more post decoding control with the gen chroma scripts that interact with the chroma decoder to combine the two TBC files in real time for FFMPEG to take and encode to a normal video file.

Full-Frame

1135x624 PAL

910x524 NTSC

Active Image Area (Default)

928x576 PAL SD

760x488 NTSC SD

Full Vertical (VBI Area)

928x624 PAL SD

760x528 NTSC SD

VITC/Closed Captions are extracted with ld-process-vbi and test signal readout and white SNR is obtained with ld-process-vits (if VITS is present)

Technical Data Stream Information

The format is a stream of 16-bit unsigned values; each value representing a single 8-bit grey-scale value in a header-less data file.

The 16-bit greyscale values GREY16 used by the output format are scaled representations of the standard 8-bit digital component values i.e. an 8-bit right shift of the value will provide the standard 8-bit digital component intensity values.

So you end with a composite 4fsc "full-frame" digital video file of the video signal.

1135x625 For PAL (17727262 Hz) (25i) (560mbps) (4.2GB/min) (252GB/hour)

910x525 For NTSC (14318181 Hz) (29.97i) (453mbps) (3.4GB/min) (204GB/hour)

Sample rate is always 4fsc, it's just stored a little weird in the .tbc for convenience: a 526th empty line in NTSC and a 626th line in PAL that has 4 samples - 2 from each field.

Note: Header-less data files are very resilient data i.e power loss or system issue and bit corruption will only damage or lose few pixels frames of information.

Digital TBC is an uncompressed 16-bit GREY16 header-less video with the .TBC extension, with a /JSON descriptor file.

TBC Variant	Frequency	Bitrate	Aspect Ratio	Total Lines (per frame)	Active Samples (per line)	Active Lines	Frame Rate
NTSC	14318181 Hz	453 Mbit/s	4:3 or 16:9	525	760	488	29.94i
PAL	17727262 Hz	560 Mbit/s	4:3 or 16:9	625	928	576	25i

Half lines dont currenty exsist in the TBC format, so there is padding effectivly an extra dummy line included.

NTSC is 526 lines and PAL is 626.

The extra 4 PAL samples (two from each field) would go on 626

These have to be removed to play the files back via ADC.

Gen Croma Scripts & Chroma-Decoder

The gen_chroma_vid.sh script does several things, run the luma TBC though dropout compensation, combine Croma & Luma TBC's image data with FFmpeg with a filter complex and then pipes the merged image to encode a full-colour video stream.

Dropout correction/compensation can be done separately with ld-disk-stack and median stack via vapoursynth allowing for stacking to compensate for normal running operation dropouts.

To encode a black and white luminance only (greyscale) with video use the chroma decoder

ld-chroma-decoder tapename.tbc y4m OutputName.mov (-p - PAL or -n for NTSC)

This gives you an uncompressed YUY 4:2:2 video file

./gen_chroma_vid.sh tapename.tbc -f OutputName.mov

This gives you a Lossless Compressed FFV1 YUY 4:2:2 encoded colour video file in the .mkv container.

Standard Active Area output is 70-100mbps

Full-Frame output is 100-130mbps

Note! the experimental full 1135x625 PAL 910x525 NTSC frame output currently has issues with frame order and it's a few pixels off this will be improved in the future.

Genarating Test Data

Vapoursynth Colourbars

ld-chroma-encoder

HackTV