dc30-linux

A new Linux driver (V4L2 + ALSA, out-of-tree DKMS kernel modules) for the miro DC30 and DC30 plus PCI video capture cards, together with the recording application dc30-capture.

The main goal is audio recorded in step with the video, above all for digitizing old VHS and S-VHS tapes. The historical open-source zoran driver never supported the DC30's audio. The original Windows driver no longer runs on current PCs and was not reliable with poor input signals. This driver is written from scratch with audio/video sync as a core part of its design.

Status

Version 1.0.0. The driver and the application are in daily use for digitizing tapes. Tested with PAL from a VCR on S-Video, on a board of revision 601694-6.0 behind a PCIe-to-PCI bridge. Recordings of more than an hour run without gaps and with the sound in sync at the end.

NTSC and SECAM can be selected, but are untested. Video output is not supported (see Roadmap).

Features

Driver

• Raw video: YUYV 768×576 (PAL), interlaced, a steady 25 fps. Field jumps of a poor source are detected and no field is lost.
• MJPEG: real-time compression by the card's JPEG codec (ZR36050 + ZR36016), set by data rate (1000–6300 kB/s). Every field is a complete JPEG with its own tables. The driver pairs the fields by parity, even when the codec gets them wrong after a field jump.
• Audio: ALSA card DC30, 16-bit stereo. By default the sample clock is locked to the video line frequency in hardware, exactly 1764 samples per PAL frame. A crystal mode offers 8–48 kHz.
• A/V metadata: a second V4L2 node delivers, for every frame, the timestamps of both fields and the exact position of each field in the audio stream, plus error counters. An application can always tell which audio belongs to which frame, even across lost frames.
• Power management: the card sleeps whenever nobody uses it. The chips are powered down individually.
• Self-tuning bus timing: the driver finds the best PostOffice timing for the PCI bridge it sits behind.

dc30-capture (Qt 6)

• Live preview, level meters with clip indicator, mixer, monitoring through the card or lip-synchronously through the PC's sound output.
• Records Matroska files on the card's time base: FFV1 (lossless, compressed on the PC, so it needs a fair share of CPU) or the card's MJPEG (compressed on the card and passed through untouched, light on the CPU, a good choice for older PCs), with PCM audio. Missing frames are repeated and logged.
• Field order from the picture: the decoder's field flag is unreliable on a VCR without time base corrector, and whole scenes can come out with swapped fields. dc30-capture determines each field's position from the picture itself and pairs the fields accordingly. dc30-capture --fix repairs finished recordings.
• Unattended recording from the command line.
• English and German user interface.

How it works

The card combines a Zoran ZR36057 PCI controller, a Micronas VPX3220A video decoder, a Zoran ZR36050/ZR36016 JPEG codec, an Analog Devices AD1843 audio codec behind a small audio ASIC, and an ADV7176 video encoder. Its audio has no DMA path: every sample byte is read by the CPU through a register window.

• docs/hardware.md: the chips, what each one does and how they are wired, including what is not in any datasheet.
• docs/driver.md: how the driver drives them: video, MJPEG, audio, A/V sync, power management, PCI timing.
• docs/module-parameters.md: every module parameter explained.

Requirements

• A miro DC30 or DC30 plus in a PCI slot. A PCIe-to-PCI bridge (on the board or as an adapter card) works.
• Linux with kernel headers and DKMS. The packages are built for Ubuntu 24.04 / Linux Mint 22 (amd64). On other distributions, build from source.
• For dc30-capture: Qt 6, ALSA and FFmpeg libraries.

Installation

From the release packages

Download both .deb files from the latest release and install them:

sudo apt install ./dc30-dkms_1.0.0_all.deb ./dc30-capture_1.0.0_amd64.deb

dc30-dkms installs the driver sources, and DKMS builds the modules for every installed kernel, also after kernel updates. With Secure Boot, DKMS signs the modules with the machine owner key (MOK). If no key is enrolled yet, Ubuntu asks you to enroll one at the next boot.

Then load the driver, or reboot:

sudo modprobe dc30

From source

Driver (needs the kernel headers and dkms):

sudo mkdir -p /usr/src/dc30-1.0.0
sudo cp src/*.c src/*.h src/Makefile src/dkms.conf /usr/src/dc30-1.0.0/
sudo dkms install dc30/1.0.0
sudo modprobe dc30        # also loads dc30_vpx3220

dc30-capture (packages on Ubuntu 24.04: cmake, qt6-base-dev, qt6-tools-dev, qt6-l10n-tools, libasound2-dev, libavcodec-dev, libavformat-dev, libswresample-dev):

cmake -S app -B app/build -DCMAKE_BUILD_TYPE=Release
cmake --build app/build
sudo cmake --install app/build

dc30-metadump: make -C tools.

The Debian packages themselves are built by packaging/build-debs.sh 1.0.0 (needs dpkg-dev and nfpm).

Usage

dc30-capture: start it from the desktop menu ("DC30 Capture"), choose the input, the codec and the target folder, and record. Without a window:

dc30-capture --record 3600 --dir ~/Videos --codec ffv1     # one hour, FFV1
dc30-capture --record 600 --codec mjpeg --rate 6000        # MJPEG at 6000 kB/s
dc30-capture --fix recording.mkv                           # re-pair fields by the picture

For damaged tapes, use FFV1. On rare disturbances of the field timing, the hardware codec drops three frames, while the raw path loses nothing.

Other applications: the video node is the one named dc30 (v4l2-ctl --list-devices). Audio is hw:DC30:

v4l2-ctl -d /dev/videoN --set-input=1                # S-Video
arecord -D hw:DC30 -f S16_LE -c 2 -r 44100 audio.wav

The audio clock follows the selected video input. Set the input even for an audio-only recording.

In the ALSA mixer, capture source "External" is the card's external audio jack and "Internal" the internal audio connector.

Troubleshooting

• Audio xruns or a high CPU load of the dc30 drain thread: see PCI timing.

• rmmod dc30 fails because the device is in use: PipeWire/WirePlumber keeps the control device of every sound card open. A WirePlumber rule can keep it off the DC30. dc30-capture, arecord -D hw:DC30 and other applications that use ALSA directly keep working. The card just no longer shows up in the desktop's sound settings.

  WirePlumber 0.4 (Ubuntu 24.04, Linux Mint 22; check with wireplumber --version), file ~/.config/wireplumber/main.lua.d/51-dc30-disable.lua:

  rule = {
    matches = {
      { { "api.alsa.card.id", "equals", "DC30" } },
      { { "api.alsa.card.name", "equals", "miro DC30" } },
    },
    apply_properties = {
      ["device.disabled"] = true,
    },
  }
  
  table.insert(alsa_monitor.rules, rule)

  WirePlumber 0.5 and later, file ~/.config/wireplumber/wireplumber.conf.d/51-dc30-disable.conf:

  monitor.alsa.rules = [
    {
      matches = [
        { api.alsa.card.id = "DC30" }
        { api.alsa.card.name = "miro DC30" }
      ]
      actions = {
        update-props = {
          device.disabled = true
        }
      }
    }
  ]
  

  Then systemctl --user restart wireplumber.

• Statistics and diagnosis: /sys/kernel/debug/dc30/<PCI address>/, see docs/driver.md.

Roadmap

• Video output and playback, including MJPEG decompression
• Audio video lock for NTSC, and NTSC testing in general
• Optional loop-through of the input to the card's video outputs
• A "no signal" warning that does not disturb a running capture

Contributing

Bug reports and pull requests are welcome. Reports from other boards, PCI bridges and NTSC sources are especially useful. Please include the output of dmesg | grep -i dc30 and, for capture problems, the debugfs stats and audio_stats files.

Acknowledgements

This driver stands on the shoulders of others.

• The GPL zoran driver for the Zoran ZR36057/ZR36067 cards, by Dave Perks, Rainer Johanni, Wolfgang Scherr, Serguei Miridonov, Ronald Bultje, Laurent Pinchart, Maxim Yevtyushkin and the mjpeg-users community. dc30_vpx3220 is a port of its VPX3220 driver by Laurent Pinchart. The video front end set-up, the reset sequence and the I2C bus are based on zoran_device.c and zoran_card.c. Its DC30 card table confirmed the board's GPIO and input wiring. Without this driver, the DC30 would have been a much harder start.
• The Linux kernel's tea6415c driver, for the byte format of the video crosspoint switch.
• The chip datasheets of Zoran (ZR36057, ZR36050, ZR36016), Micronas (VPX3220A), Analog Devices (AD1843, ADV7176) and ST (TEA6415C).
• The JPEG standard (ITU-T T.81, Annex K) for the quantization and Huffman tables.
• Qt, FFmpeg and ALSA, on which dc30-capture is built, and nfpm for the packages.

Disclaimer

This project is not affiliated with, endorsed by or connected to miro, Pinnacle Systems, Zoran, Micronas, Analog Devices, STMicroelectronics or any of their successors. All product names and trademarks belong to their owners and are used only to describe compatibility. Parts of the hardware behaviour were worked out by observing the original Windows driver, for the sole purpose of interoperability. Use this software at your own risk.

License

GPL-2.0-only, see LICENSE. The header src/dc30_meta.h, which applications include, is GPL-2.0-only WITH Linux-syscall-note.

Part of the save old hardware collection

This project is part of a larger idea: I own a lot of old hardware that would be unusable if I hadn't written drivers and tools to bring it back to life. From the early nineties and, even more so, the early 2000s up to today, a lot of Windows-only or use-once-then-throw-away hardware was developed and sold, only to become electronic waste a few years later. And it kept happening, because the manufacturers kept moving on to newer products and dropping support for older devices entirely. Expensive audio equipment, lab gear, other specialized kit that's hard to find, you name it.

As a tinkerer, electrical design engineer and software developer (I do the latter two for a living), I decided to stop accepting this and do something about it. Hence, I've created this logo, and I attach it to every project where saving a device from becoming waste is a central goal.

Feel free to use this logo as well, and spread the word! Thanks for reading this. People like you make a difference in this world. Become a part of us — try to write software for the stuff you own, and consider publishing it as open source.