SDVPCM (or Standard Definition Video to Pulse Code Modulation) is GUI cross-platform software designed for decoding PCM digital audio data from SD video sources. It takes video file containing capture of some PCM format recording and produces WAV file with decoded audio, performing error correction and dropout masking set by user.
At the dawn of digital audio the only viable option to store relatively high bandwidth digital signal was to record it to the video tape. From 1970s various systems were developed that accompanied some kind of video tape recorder with additional PCM audio processor to achieve capabilities of digital audio recording and playback.
Notable ones:
- Denon DN-023R (1972)
- Sony PCM-1 (1977)
- Sony PCM-1600 (1978), PCM-1610 (1980), PCM-1630 (1982)
- EIAJ STC-007 (1980), Sony PCM-F1 (1981)
- Technics SV-P100 (1981)
Denon DN-023R was a professional 8-channel digital audio recorder. Sony PCM-1 was the first consumer-oriented 13-bit PCM audio processor. Sony PCM-16x0 series were professional 16-bit PCM audio processors, that were used for mastering Audio CDs. EIAJ STC-007 was widely supported standard of consumer PCM audio processors with 14-bit audio, Sony PCM-F1 was its 16-bit extension. Technics SV-P100 was a combined VHS deck with STC-007 digital audio processing and some additional mark and search features put into one device.
The idea was to encode digital audio bitstream as some sort of video patterns that could be recorded as SD video and than played back and decoded. Digital nature of the signal allowed addition of error detection and error correction codes into the bitstream and interleaving data to avoid signal loss in case of problems with reading signal from the tape.
- Sony PCM-1 (13 bits)
- Sony PCM-16x0 (16 bits) (both SI and EI formats)
- EIAJ STC-007 (14 bits) and Sony PCM-F1 (16 bits)
- M2 (16 bits)
- Linear decoding of SD video into digital audio skipping analog domain.
- Decoded digital audio is stored into WAV file.
- Live playback is possible but it's only for evaluation purposes and it's not the primary use case of the software.
- All error detection and error correction features of each format are supported and sometimes more than that.
- Data decoding from video files with lossy digital compression.
- Data decoding from heavily degraded and damaged sources.
- Possibility of full audio data recovery even if not all video lines are captured in the file (most PCM formats use inactive region of the video).
- Video resolution and aspect ratio do not matter as long as video is not vertically resized and data bits are not blended with each other (decoder can't help with dropped or duplicated frames in your capture though).
- Selectable binarization presets to balance speed and data recovery efforts.
- Many user-controllable parameters (including PCM format, source video field order, active error correction stages, dropout masking method and more) but most of those can be left in "auto" thanks to auto-detection algorithms.
- Statistics display for decoding process.
- Visualizations for source, binarized data and data blocks with error correction indicators.
- Multithreaded data processing.
- Interface translation support (language is selected by system locale).
- Qt 5 and FFMPEG libraries are used to achieve cross-platform support.
- Automatic Gain Control (AGC): levels of "0" and "1" bits as well as reference (threshold) level are automatically detected on per-line basis using statistics on brightness spread information.
- Reference level can be calculated fast or brute-force sweeped through all available levels according to preset binarization mode.
- Time Base Correction (TBC): automatic horizontal data coordinates detection that can be performed on per-line basis or averaged by the frame according to preset binarization mode and PCM format.
- Bit Picker: automatic detection and brute-force picking bits that were cut from the edges of the source video due to incorrectly setup video capture (for PCM-1 and PCM-16x0).
- Automatic reference level hysteresis is used to extract more data from noisy and/or low-bandwidth sources, enabling adaptive reference level depending on the state of the previous bits (maximum hysteresis depth depends on preset binarization mode).
- Pixel-Shifter (Micro TBC): another mechanism that allows more accurate data extraction from noisy and damaged sources, performing multiple shifts of each data bit coordinates until valid data is read.
- Extensive statistics collection and analysis on each stage to detect and filter out false-positive CRCs and CRC collisions to prevent erroneous data propagating through.
- Big list of fine settings, including setting limits for "0" and "1" brightnesses, minimum contrast, limits for reference level, maximum allowed picked bits, margins for data coordinates search, manual data coordinates, capabilities to decode data from different color channels (R/G/B/Y) or to ignore CRC errors.
- Sophisticated algorithms for filtering noise and empty lines from the video and automatically detecting vertical data coordinates for each PCM format.
- Automatic detection of field order, video standard, data resolution for STC-007/PCM-F1 formats.
- Selectable dropout masking method (skip, hold level, linear interpolation).
- Launch application
- Click {Open a video...} and select a video file with PCM data in it
- Set {PCM format} to desired format
- Tick {*Save to a .WAV file} and/or {Live playback}
- Click {START/STOP source video}
After all frames are decoded, process will stop and {START/STOP} button will reset. Decoded WAV file will be placed in the same path as the source video file and will have the same name with decoder version added to it. If WAV file is already present it will be overwritten!
User can stop decoding at any moment by pressing {START/STOP} button. User also can pause decoding with {Pause} button or by ticking {Stepped playback} option while in decoding. User can change decoder settings before or while decoding but best practice is to set everything before starting decoding.
When in doubt, reset decoder settings to defaults by selecting {Reset decoder settings} in the {Settings} menu.
Updated video on STC-007:
Outdated video:
SDVPCM is still in development and debugging stage, GUI is not finalized yet. There are many debug menus and indicators all over the interface.
Most of the features should work as intended.
Target platform is Windows, not guaranteed to be working on other platforms. Development is performed with Qt 5.5.0 toolset.
- If you have captures of some SD video, containing digital audio encodings from formats that are not supported by the software and you can share those recordings - please do.
- If you have captures of supported PCM formats but you have throubles with properly decoding it, you can share problematic video and probably get some help with that, also improving decoder in the process.
- English and Russian translations are maintained by the developer but you can contribute translations to other languages using standard Qt Linguist tools.
- If you can test the decoder on other platforms and provide bugfixes to enable correct operation on those - please do.
Program copyright 2020-2023.
This program is free software. Licensed under the Apache License, Version 2.0 (the "License");