Last Updated: 20050929, mei
Saturday, October 8, 3:30 pm — 5:30 pm
W8 - 5.1 DOWNMIX IN PRACTICE
Jeff Levison, Phontrum - Woodstock, VT, USA
Charles Robinson, Dolby Labs - San Francisco, CA, USA
5.1 multichannel sound has become very popular in the market, coexisting with the 2-channel stereo standard. Producers and providers are confronted with the necessity of delivering optimum quality not only for the new format but also for the old one. In other words, optimum aesthetical downward compatibility is required. It is without a doubt that simultaneously offering the multichannel as well as the 2-channel format (DVD-A, SACD, simulcast broadcasting) is advantageous in comparison with known downmix matrix techniques (e.g., ITU matrix) because optional mixes can be provided in principle. However, the provision of an extra 2-channel handmade mix is a significant matter of cost. At least broadcasters are not able to afford production, archiving, and distribution of two formats in the case of simulcast broadcasting. They need automatic downmix methods that guarantee satisfying stereophonic quality for any material. Furthermore, matrix based surround sound downmix-upmix systems such as 4-2-4 and 5-2-5 are in use, and automatic downmix strategies should ensure sufficient aesthetical downward compatibility as well as full backward compatibility with existing decoders. Last not least, sophisticated 5-2-5 spatial coding systems will be applied in the future. As a potential candidate for broadcast applications the spatial coding system requires optimum performance with respect to the downmix algorithm.
Related questions will be addressed in the workshop. Panellists will demonstrate practical results of automatic and handmade downmixes in comparison with the original 5.1 version as well as among each other. The following topics will be discussed, aiming for an acceptable automatic downmix solution:
• How close are we to achieving a separate 2.0 handmade mix?
• How close are we to a standard ITU downmix?
• How close are we to a sophisticated automatic downmix?
• Automatic downmix for economic and technical reasons
• Intelligent automatic downmix strategies
• Spatial coding—new possibilities or new problems?
• Is automatic downmix monitoring during 5.1 production
• The balance of 5.1 mix quality and 2.0 downmix quality?