Using HDMI With ATI Radeon HD Linux Drivers

One of the special abilities of ATI's R600 GPU family is the integrated 5.1 surround sound audio support through HDMI. Many Radeon HD 2000 and HD 3800 series graphics cards also ship with a DVI to HDMI dongle, so that one can experience the full video playback capabilities of these discrete graphics cards. But what level of HDMI support can Linux users expect when using these latest ATI graphics cards? We have done some testing internally and have the initial ATI Linux HDMI video and audio results to report in this article.

The graphics card used for this Linux HDMI (High Definition Media Interface) testing was the ASUS Radeon HD 2600PRO 256MB, which was connected via a DVI-to-HDMI dongle to a Sharp Aquos LC37D43U 37" LCD HDTV. For the video portion of the HDMI, we had tested both the fglrx and RadeonHD drivers and ALSA for audio.

Using the ATI Linux "fglrx" driver, the system running Ubuntu 7.10 had booted without any issues and was running at 1920 x 1080 through no end-user intervention or manually specifying any display modes. Entering the AMD Catalyst Control Center Linux Edition, there were no problems with managing the Sharp HDMI display and everything had worked out smoothly.

At 1920 x 1080, the Radeon HD 2600PRO had no problems running Compiz Fusion at this resolution. Enemy Territory: Quake Wars was also running at this resolution and high-quality settings, with an average frame-rate of ~26 FPS. Everything on the display front had worked out, though we didn't expect any problems as this was just running through an included DVI-to-HDMI dongle.

Unfortunately, the HDMI audio at this time wasn't nice. Ubuntu 7.10 ships with ALSA 1.0.14, so we had manually compiled ALSA 1.0.15. A patch for R600, RS600, RS690, RS780 HDMI audio support was originally released by AMD earlier this year, and is present in this latest version of ALSA (Advanced Linux Sound Architecture). However, ALSA was unable to properly detect and utilize this ATI R600 HDMI audio adapter through the hda-intel driver. For the record, there are bugs present in ALSA 1.0.15 that affect other adapters using HDMI audio as well. For right now, using the HDMI audio with the latest ATI Radeon HD graphics cards isn't a trouble-free experience, but hopefully once ALSA 1.0.16 is out the door these problems will be eliminated.

After the success using the proprietary ATI driver, we had turned to the latest git code for xf86-video-radeonhd. Using this open-source driver, the detected EDID information from the Sharp LC37D43U LCD HDTV had the system running at 1280 x 720. We had then manually added a 1920 x 1080 mode in the xorg.conf, but still the RadeonHD driver had turned back to this lower resolution. Aside from the resolution disparity, the RadeonHD driver worked fine as would be expected for this HDMI adapter.