Elgato Game Capture HD - Linux drivers

Reverse engineering the Elgato Game Capture HD to make it work under Linux.

We all love out Elgatos, we all love our Linux machines. I've been in contact with Elgato several times and talked with them about this topic; they don't plan on adding Linux support and they also can't help Linux developers, due to NDA restrictions.

So, the only chance is by getting our hands dirty and reverse engineer it on our own. Everyone who can help us is welcome, it doesn't matter if you want to program, improve the documentation, research, provide webspace or simply test and give us feedback.

First Step

In order to write a driver, we need to fully understand, how the device works. I have now got my hands on a working OpenVizsla USB 2.0 analyzer and was able to capture all necessary USB packets. Our job is to mimic the traffic between the GCHD and the host.

How the device works

After studying the video output and USB packets, the Elgato Game Capture HD seems to be one hell of device! This little thing directly outputs compressed video and audio data, in the following format:

General
Format                         : MPEG-TS
Overall bit rate mode          : Variable
Overall bit rate               : 22.4 Mbps

Video
ID                             : 100 (0x64)
Menu ID                        : 2 (0x2)
Format                         : AVC
Format/Info                    : Advanced Video Codec
Format profile                 : High@L4.0
Format settings, CABAC         : Yes
Format settings, ReFrames      : 2 frames
Codec ID                       : 27
Duration                       : 12s 217ms
Bit rate mode                  : Variable
Bit rate                       : 21.1 Mbps
Maximum bit rate               : 30.0 Mbps
Width                          : 1 280 pixels
Height                         : 720 pixels
Display aspect ratio           : 16:9
Frame rate                     : 60.000 fps
Color space                    : YUV
Chroma subsampling             : 4:2:0
Bit depth                      : 8 bits
Scan type                      : Progressive
Bits/(Pixel*Frame)             : 0.382
Stream size                    : 30.7 MiB (92%)
Color primaries                : BT.709
Transfer characteristics       : BT.709
Matrix coefficients            : BT.709

Audio
ID                             : 101 (0x65)
Menu ID                        : 2 (0x2)
Format                         : AAC
Format/Info                    : Advanced Audio Codec
Format version                 : Version 4
Format profile                 : LC
Muxing mode                    : ADTS
Codec ID                       : 15
Duration                       : 12s 245ms
Bit rate mode                  : Variable
Bit rate                       : 220 Kbps
Channel(s)                     : 2 channels
Channel positions              : Front: L R
Sampling rate                  : 48.0 KHz
Compression mode               : Lossy
Delay relative to video        : -333ms
Stream size                    : 329 KiB (1%)

Steven Toth from Kernel Labs noted, that the device is outputting native ISO13818 TS packets. Once the device is set up, we should be able to get the video stream without any encoding. Thank you Steve for the hint!

Drivers

Currently, we've fully implemented the transfer of both binary files. The next step is to figure out, how the host is configuring the GCHD and receiving audio and video. We have full capture logs available (look at issue #2 on GitHub).

What we need and how you can help

The primary platform, where we share our efforts, will be GitHub. If you're interested, just shoot us a message and tell us, what you want to do and we will add you ;). This project surely can't be realized by one person in a reasonable amount of time.