There are far too many changes in ALSA 1.0.20 to talk about them all, but some of the prominent ones that caught our attention affect the C-Media Oxygen driver, HDA Codec, and HDA Intel. The CMI8788 (Oxygen) driver in ALSA is what supports some of the high-end sound cards like the Razer Barracuda AC-1 and ASUS Xonar. Just two years ago this driver was rewritten after having a troubled start. In ALSA 1.0.20 the Oxygen driver now has support for the Xonar Essence STX sound card, headphone output support on Claro cards, and various other improvements.
ALSA's HDA Codec driver carries support for various new laptops and audio devices (including some from Apple), quirk handling for other devices, and a whole array of fixes. The HDA Intel driver has a few ATI-specific fixes and the generic HDA driver has a few HDMI fixes.
Beyond the mentioned changes, numerous other drivers and core parts of ALSA were touched in this version 1.0.20 update. What continues to be missing from ALSA, however, is support for the Creative X-Fi sound cards. With this latest ALSA release there still is no support for the X-Fi chipsets even though they are now several years old and Creative Labs has released an open-source driver. More information on this problem can be read in Creative Labs Continues To Shaft Linux.
All of the changes between ALSA 1.0.19 and 1.0.20 can be read about on the ALSA project Wiki. Download the latest ALSA drivers, libraries, utilities, tools, firmware, and plug-ins from the ALSA home-page.