Stijn,
Just a note, some manufacturers are overclocking the refresh rate on their displays, to 120KHz or 240KHz instead of 60KHz. When they do this it introduces a delay into the audio stream, effectively destroying the ability of the acoustic echo canceller to do it's job. When this happens you will notice an echo when using the HDMI based audio. You can resolve this issue by using external speakers, playing around with the settings on the disply or replacing the display with a commercial display, not a consumer display.
Here is a note directly from the Cisco C series admin guide on this issue:
New consumer TVs are usually equipped with “Motion Flow” or similar technology to insert new video frames between standard frames to create smoother images. This processing takes time and to maintain lip synchronization, the TV will delay the audio so that the audio and video arrives at the same time.
The echo canceller in the Cisco endpoints can handle such delay up to 30 ms. Many consumer TVs are not made for real time video communication and may introduce more than 30 ms of delay.
If you use such a TV together with a C-series codec it is recommended that you turn off “Motion Flow”, “Natural Motion” or any other video processing that introduces additional delay.
Some consumer TVs also support advanced audio processing like “Virtual Surround” effects and “Dynamic Compression” to improve the TV experience. Such processing will make any acoustic echo canceller malfunction and should hence be switched off.
Some monitors are equipped with a setting called ‘Game Mode’. This mode is specifically designed to help reduce the response time and will usually help to reduce the delay.
Thanks,
Justin
Thank you,
Justin Ferello
Technical Support Specialist, ScanSource KBZ
