vhs decode
hs-decode
A fork of LD-Decode, the decoding software powering the Domesday86 Project.
This version has been modified to work with the differences found in the tracked RF drum head signals taken directly from colour-under & FM modulated composite videotape formats.
Caution
Not to be confused with the TV Modulator/Demodulator pack or the "antenna connectors" on the back of the VCR!
SMPTE ColourBars (16:9) Test Tape With WSS (PAL) exported full-frame (1112 x 624)
VHS 625-line and 525-line - NTSC, NTSC-J, PAL and PAL-M. Generally well supported
SVHS 625-line and 525-line - NTSC, NTSC-J, PAL and PAL-M. Basic support
U-Matic Low Band 625-line and 525-line - PAL and NTSC. Supported
U-Matic High Band 625-line - PAL. Basic support
Betamax 625-line and 525-line - PAL & NTSC. Suppported
Video8 & Hi8 625-line and 525-line - PAL & NTSC. Basic support
1" Type C (SMPTE Type C) 625-line and 525-line - PAL & NTSC. Basic support (More Samples Required!)
1" Type B (SMPTE Type B) 625-line and 525-line - PAL & NTSC. Basic support (More Samples Required!)
EIAJ 625-line - PAL. Supported (NTSC Samples Required!)
Philips VCR 625-line - PAL. Supported
Example Videos: VHS-Decode / The Rewinding / Video Dump.
Example Workflow Flowcharts and Overview Graphics
The frequently asked questions page and the Wiki, will help break things down and explain the real world benefits of direct RF capture preservation and software decoding compared to conventional high-cost hardware based workflows, so if you have just found this project welcome to the affordable future of tape media preservation.
This repository also contains an experimental CVBS decoder, cvbs-decode, which shares code with ld-decode and vhs-decode. Capable of decoding basic RAW digitized NTSC and PAL composite video, including colour if the source is somewhat stable.
RAW CVBS has been captured using CX Cards & CXADC, however, only at lowest gain states and or with external signal feed into it to stop its hardware decoder from triggering.
Caution
CVBS capture is not possible with the DomesDayDuplicator Rev3 due to input filtering on the hardware, but is possible with the MISRC boards.
Test samples & signals can be digitally generated using HackTV or downloaded from The Internet Achive.
Thanks to VideoMem's work on Superheterodyne Decoding Tools we now have a working HiFi Audio Decoder which provides decoding for VHS & Video8/Hi8 HiFi FM tracks which takes uncompressed or FLAC compressed RF captures of HiFi FM signals and outputs standard 24-bit 44.1-192khz FLAC stereo audio files.
RTLSDR capture & decoding (cross plafrom as its 100% GNURadio based) can run in realtime on most systems (1~3 sec delay) and provide live playback, Alongside 8msps RF files and a 48khz 24-bit FLAC file of the decoded audio.
Preferably adjusted per tape and in excellent mechanical and head condition, prosumer metal track decks are preferable as they were built generally better in terms of mechnical stability than cheaper later consumer decks that use more plastics, the only crtical requirement is avalible test points or a head amplifyer that is easy to tap into, this goes for any and all tape formats.
Tip
SVHS tapes can be RF captured on standard VHS HiFi decks.
Tip
SVHS NTSC Decks - Currently inflated, but you can import PAL decks with NTSC support for 1/3rd the price though this only applys if conventional refrance SVHS captures are required.
Important
Always clean your tape track/drum/heads before and afterwards with 99.9% isopropanol and lint free cloths/pads/paper. This ensures less dropouts from dirty heads or tracks including the track of the head drum.
Its good practice to avoid cross contamination of tapes, especially if dealing with mouldy or contaminated tapes.
It also helps to make sure to re-lubricate metal and plastic moving joints cogs and bearings with appropriate greases and oils to avoid mechanical failures. Please read the Cleaning & Servicing Guide.
Tip
Currently is there is 2 standardised hardware tools but RF Capture is not just limited to these 2 devices.
Capture is done using an simple GUI application.
Linux Application / Windows Application / MacOS Application
Built and geared torwards capturing RF from Laserdisc players, it does however also work perfectly well for digitizing many forms of tape FM RF signals. It consists of a custom analogue to digital board with an amplifier, an off-the-shelf DE0-NANO FPGA development board, and a Cypress FX3 SuperSpeed Explorer USB 3.0 board.
Warning
Dont use USB storage or video devices on the same USB bus as the DdD, it will crash the capture!
Warning
Several users have reported issues with dropped samples when using the ddd do capture on Windows, so as of now using it on Windows is not recommended.
Where to Buy? & More Info
Capture & Config uses simple command-line arguments and parameters CXADC
The most cost-effective approach is using a video capture cards based on a Conexant CX23880/1/2/3 PCI chipset.
Today with a modified Linux driver, these cards can be forced to output RAW signal data that can be captured to file, instead of decoding video normally as they otherwise would.
While you can use any generic card with the correct chips, today we recommend the ‘‘New’’ Chinese variants that can be found on AliExpress that have integrated Asmedia or ITE 1x PCIE bridge chips allowing modern systems to use them, and consistent performance.
These cards combined with a dedicated amplifier and some basic to advanced mods become amazing archival tools and was the first turn-key workflow with the clockgen mod enabling Video + HiFi RF + Baseband (linear or deck decoded hifi) to be captured in perfect hardware sync!
Where to Buy? & More Info
Tip
Please Read VCR Reports / The Tap List / Hardware Installation Guide
Information on various VCRs that have been documented alongside high resolution pictures of VCR's that have had RF taps installed, guidance on recommended cables/connectors & tools to use are also included.
The setup process for RF capture involves running a short cable internally from points that provide the unprocessed video and or audio signal to a BNC jack at back of a metal/plastic VCR chassis or cable threaded out a vent, this allows direct access to the FM RF signals conveniently & reliably, we call this a Tap Point or RF Tap, for some decks and camcorders however DuPont conectors and ribbon jigs can be used but are less mechanically secure.
- VCR Unit ==> Head Drum ==> RAW Signal From Heads ==> Amplification & Tracking IC ==> Tracked FM RF signals ==> - FM RF Test/Signal Points ==> FM RF Capture ==> - Software Decoding ==> Lossless 4fsc TBC Files ==> YUV Conversion ==> Standard Audio/Video Files.
Decks follow this naming or close to it not every possible name is covered.
Video FM RF Signal:
RF C, RF Y, RF Y+C, V RF, PB, PB.FM, V ENV, ENV, ENVE, ENVELOPE, VIDEO ENVE, VIDEO ENVELOPE
HiFi Audio FM Signal:
HiFi, A.PB, A FM, A.PB.FM, Audio FM, A-Out, A ENV, HIFI Envelope, FM Mix Out
Caution
Just because a test points has this name doesn't automatically mean it will have the signal we want, especially when it comes to hi-fi audio, be sure to check with the service manual if possible and do small test captures before finalizing any RF Tap setup.
What tools do I need?
50ohm BNC connectors, normally a premade bulkhead, or solderable thread mounted.
50-100cm of RG316 or RG178 50 ohm coaxial cable.
10uf Capacitors standard ceramic assorment or audio grade like Nichicon if you like.
Connection Cables
Direct BNC to BNC
50Ohm BNC to BNC Cable
On CX White Cards you use the RCA (Vmux 1) for the RF input with C31 capacitor removed, but a BNC can be easily added.
Tip
The Hardware Installation Guide visually goes over all the install steps for tape decks to Sony 8mm camcorders.
Adding a 10uf (0.1uf to 100uf range) capacitor to the test point or amplifier is recommended can help improve signal integrity (a handful VCRs have this on the test point already).
Center is Signal, Outer is Ground, this goes for jacks and for coaxial cable in general.
For a electrolytic capacitor Positive leg (longer) goes on test/signal point, Negative leg (shorter) on cable to connector/probe.
However this does not matter for Ceramic which are bi-directional & recommend today.
While type and voltage does not matter drastically it's best to use new/tested capacitors.
Note We use Aliexpress links for wide availability globally, but local vendors are a thing.
Note With some Sony decks you can use Dupont connectors on the test point pins making an easy RF tap.
Note Do not make sharp bends in any RF cabling, keep total cable runs as short as possible Ideally 30-60cm, more cable = more signal loss.
Note Some UMATIC decks have an RF output on the back, however this only provides Luma RF for dropout detection and not the full signal required for RF capture.
Windows Binarys Download
The ld-tools suite, tbc-video-export and combined exe version of ld-decode / vhs-decode / cvbs-decode / hifi-decode which is simply decode.exe exists for Windows.
This allows the use of ld-analyse's GUI to view TBC files, ld-lds-converter to convert and compress DdD captures inside Windows with drag and drop bat scripts.
The decode suite can also be built & run natively on Windows 10/11 or built inside WSL2 22.04.1 LTS (Windows Subsystem for Linux) however issues with larger captures i.g 180gb+ may require expanding the default virtual disk size.
See building on MacOS page on MacOS Build install docs are only currently for ARM based apple products such as the M1/M2 lines.
VHS-Decode, as with LD-Decode, has been developed and tested on machines running the latest versions of Ubuntu, Debian and Linux Mint. The tools should however be able to be built on other distributions too provided they have access somewhat recent versions to the needed dependencies, including at least python 3.8.
There is a Linux compatibility doc for various tested distributions of Linux.
Other dependencies include Python 3.8+, numpy, scipy, cython, numba, pandas, Qt5, qwt, Cmake, and FFmpeg.
Some useful free tools to note for post processing are StaxRip & Lossless Cut & of course DaVinci Resolve - these give you basic editing to quickly handle uncompressed files across operating systems, and for Windows users an easy FFmpeg/AviSynth/Vapoursynth encoding and QTGMC de-interlacing experience, and full colour grading and post production ability.
Install all dependencies required by LD-Decode and VHS-Decode:
sudo apt install git qtbase5-dev libqwt-qt5-dev libfftw3-dev libavformat-dev libavcodec-dev libavutil-dev ffmpeg pv pkg-config make cmake sox pipx g++ python3-dev
Ubuntu 22.04/Linux Mint 21/Debian may also need this library installed if one wants to use the GUI version of hifi-decode:
sudo apt install libxcb-cursor0
For Arch Linux
pacman -S base-devel git qt5-base qwt fftw ffmpeg pv cmake sox python python-pipx
Set up pipx
pipx ensurepath
(Alternatively, a python virtual environment can be used instead of using pipx)
Install TBC-Video-Export
pipx install tbc-video-export
(There is also self contained builds if install issues arise)
Optional dependencies for GPU (Nvidia Cards) FLAC compression support:
sudo apt install make ocl-icd-opencl-dev mono-runtime
Also Requires FlaLDF Download & Install via .deb for Linux
The vhs-decode respository also has hifi-decode, cvbs-decode, ld-decode included.
Download VHS-Decode:
git clone https://github.com/oyvindln/vhs-decode.git vhs-decode
Install VHS-Decode:
cd vhs-decode
Build and install vhs-decode via pipx
pipx install .[hifi_gui_qt6]
Compile and Install ld-tools suite: (Required)
mkdir build2 cd build2 cmake .. -DCMAKE_BUILD_TYPE=Release -DUSE_QT_VERSION=5 make -j4 sudo make install
Go back to the main directory with
cd ..
To update do git pull while inside of the vhs-decode directory.
To update to the latest git version of vhs-decode/ld-decode/hi-fi decode, run pipx install . inside the vhs-decode directory after running git pullTo update the tools to the latest version, the steps under "Compile and Install ld-tools suite: (Required)" has to be re-ran after a git pull. The tools are not updated very often.
Note
debian/ubuntu does not have a qt6 version of qwt in repositories as of yet so you have to inform the build script to use Qt5 if both qt5 and qt6 are installed with -DUSE_QT_VERSION=5 as it might otherwise try to compile with qt6 instead and failing to locate qwt. The option is otherwise not needed.
Note with WSL2 & Ubuntu, ./ in front of applications and scripts may be needed to run them or to run scripts within the folder.
Use cd vhs-decode to enter into the directory to run commands, cd.. to go back a directory.
UseCtrl+Cto stop the current process.
You dont actaully type < and > on your input & output files.
Ensure system is powered off
Physically Install CX Card
Install CXADC driver
Connect Card to RF Tap
Find Vmux Input (Via Live Preview)
Configure Capture
Capture RF Data
FLAC Compress RF Data (Archive)
CXADC Readme for information on how to install & configure the driver, this also goes into depth on modes.
Commands for real-time FLAC capture on CX Cards
Naming Guide For RF Captures!
To see if you have a connection, use the live preview mode and then hook up your RF cable, normally you will see a white flash as a signal, if not change your vmux or input within a 0-2 range with the below command.
sudo echo 0 >/sys/class/cxadc/cxadc0/device/parameters/vmux
To see a live preview of tape signal being received by a CXADC card, note that the video head tracked signal will be unstable or wobbly if settings are not the same; you may only see "signal flash" if in 16-bit mode for example.
This is quite useful if you don't own a CRT with Horizontal/Vertical shifting, as it will allow you to inspect the full area for alignment and/or tracking issues.
PAL framing for the default 28.64 MHz/8-bit mode:
ffplay -hide_banner -async 1 -f rawvideo -pix_fmt gray8 -video_size 1832x625 -i /dev/cxadc0 -vf scale=1135x625,eq=gamma=0.5:contrast=1.5
NTSC framing for 28.64 MHz/8-bit mode:
ffplay -hide_banner -async 1 -f rawvideo -pix_fmt gray8 -video_size 1820x525 -i /dev/cxadc0 -vf scale=910x525,eq=gamma=0.5:contrast=1.5
Capture 30 seconds of tape signal using CXADC driver 8-bit samples
timeout 30s cat /dev/cxadc0 >_CXADC.u8
For 16-bit, simply change the output filename extension to .u16
For FLAC captures, set the output filename extension to your desired tape format, for example .VHS
It is recommended to use a fast storage device with 40-100 MB/s or faster write capacity, in order to avoid dropped samples, ideally an dedicated SSD (via M.2 or SATA connector, not USB) formatted with the exFAT filesystem.
For DomesDayDuplicator captures on Linux simply run:
ld-compress
For DomesDayDuplicator captures on Windows simply drag and drop on:
ld-compress.bat or ld-compress-nvidia-gpu.bat
Your .lds file will be compressed to an FLAC OGG .ldf file.
For CXADC and other standard 8-bit or 16-bit RF captures use the following:
Copy Paste FLAC Compression Commands for CXADC
Editable flags are:
The --bps flag can be changed to --bps=8 or --bps=16 for 8 & 16 bit captures and --ogg is optional.
Change
Reduce size of captured CXADC data (by 40-60%):
flac --best --sample-rate=28636 --sign=unsigned --channels=1 --endian=little --bps=8 --ogg -f.u8 .flac
Output will be .vhs / .hifi etc, but include _8-bit_28msps and NTSC or PAL etc in the name, to always know what the data and tape format is.
Decompress FLAC compressed captures:
flac -d --force-raw-format --sign=unsigned --endian=little.vhs .u16
Decode your captured tape to .tbc by using:
