Hi Charles,
Sorry for any confusion. With the H.264 Pro Recorder, when you connect SDI, the device is looking for video and audio embedded on the SDI stream. Similarly, if you connect HDMI, it is looking for audio and video on the HDMI stream. In order to use the 1/4″ TRS connectors, you would need to be inputting an analog video signal at that time. This is how the auto-sensing feature is designed.
If you are looking to input 1/4″ TRS audio with your HD-SDI video feed, we can take this as a feature request, but currently this will not work with the H.264 Pro Recorder. You would need to embed this audio signal on your SDI feed prior to connecting to the device. You could accomplish this with something like our Mini Converter Audio to SDI or a similar device.
Best Regards,
Sarah
Support Representative
Blackmagic Design Inc.