Linux Plumbers Conf 2009

Excerpt

Description

We will first present challenges encountered when enabling hardware accelerators to reduce power-consumption or handle DRM-protected premium content. We show difficulties encountered with gstreamer auto-pluggin, sinks and dynamic re-routing between audio accessories.

In the next section, we will focus on platform volume control and hierarchical mixing. On most devices, the final output is the result of both digital and analog mixing in a companion chip; we present examples and show the need for PulseAudio to control not only the native streams it processes, but also additional streams that are mixed in hardware, so that the user can control volumes all the way to the speaker. We will suggest several proposals based on ALSA controls or PulseAudio extensions.

After we review several existing solutions, we will then show the need for standard communication channels between PulseAudio and audio apps to handle audio policy in a generic manner, and we will present the need to leave the choice of policy rules to the OEM or distribution maintainers. We believe such standardization would benefit not only the mobile community but improve the audio experience on all Linux devices.

Last, we will discuss a generic plumbing issue when transmitting audio/video content to a distant renderer. In the case of HDMI v1.3 for example, the receiver can provide information on the latency of audio and video rendering; this lip-sync delay information is however not channeled from the ALSA driver back to PulseAudio or gstreamer. Likewise, the receiver capabilities in terms of supported channels, frequencies and formats are not forwarded to PulseAudio. The intent of this last section is to stimulate discussions in the Linux audio community on where lip-sync handling and receiver adaptation make the most sense.

Speaker

• Pierre-Louis Bossart

  Intel Corporation
  • Website: http://www.intel.com/

  Biography

  MS Computer Engineering, UT Compiegne, France 1991
  PhD Signal and Image Processing, National Polytechnic Institute of Grenoble, France, 1994

  Post-doc, Lawrence Livermore National Laboratory, 1995-96

  Audio and system architecture related positions since 1997 with Digigram, STMicroelectronics, Freescale and Intel.