incompatibility with capture devices

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I'm seeing issues with HDMI output not being compatible with capture devices. Tested with Elgato Cam Link 4K as well as a Blackmagic capture device). Using the Tang Nano 20K. If I use the default HDMI firmware for the Tang, video is captured correctly. Any idea why this wouldn't work? The Elgato software claims that it is trying to put out an incompatible resolution of 720x481 (not 480).

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Adding more detail. Using hdmi_demo as the test case, switching to DVI_OUTPUT(1) gets the video output to display on the Elgato Cam Link 4K. When it is in HDMI mode (DVI_OUTPUT(0), the Cam Link is unable to lock onto it.

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Also, not sure if it's related, but I do see the following messages during build (both in my project and in the hdmi_demo). Keep in mind that even though these warnings are present, the code does generate working video and audio (except in the aforementioned capture devices):

WARN  (NL0002) : The module "audio_info_frame" instantiated to "audio_info_frame" is swept in optimizing("D:\Gowin\Projects\hdmi_demo\src\hdmi\packet_picker.sv":143)
WARN  (NL0002) : The module "audio_sample_packet" instantiated to "audio_sample_packet" is swept in optimizing("D:\Gowin\Projects\hdmi_demo\src\hdmi\packet_picker.sv":131)
WARN  (NL0002) : The module "auxiliary_video_information_info_frame" instantiated to "auxiliary_video_information_info_frame" is swept in optimizing("D:\Gowin\Projects\hdmi_demo\src\hdmi\packet_picker.sv":137)
WARN  (NL0002) : The module "source_product_description_info_frame" instantiated to "source_product_description_info_frame" is swept in optimizing("D:\Gowin\Projects\hdmi_demo\src\hdmi\packet_picker.sv":140)

It's not clear to me that it should work at all if these are truly being swept into optimizing, since it seems that audio would require the audio_sample_packet to be present.