External HDMI audio extractor not compatible with dvi2rgb block

[aytli]

I'm working on an HDMI processor using a Zybo Z7-20 board, with Vivado 2016.4. The starting point of this project was the HDMI demo project, using the dvi2rgb and rgb2dvi cores. Since the dvi2rgb block doesn't handle audio data, we've connected a commercially available HDMI audio extractor right before the HDMI RX port.

I'm using 3 different video sources: laptop, ipod, and ipad (with lightning to HDMI dongle). All 3 are compatible with the FPGA, I've fed them each directly into the RX port and displayed them to a monitor on the TX plug. They're also compatible with the audio extractor, I've fed them through the audio extractor and directly to a monitor. But when I combine the audio extractor with the FPGA, it either extracts audio, or it passes video, but not both at the same time. I suspect that the EDID of the dvi2rgb block is causing some issues, so I've been modifying the settings, but I can't seem to find a setting that allows the audio extractor to both extract sound and pass the video stream.

Here are some of the things I've done to the EDID:

- Padded the default 128 byte EDID with 128 more bytes, then edited dvi2rgb.vhd to use 8 bits for the EEPROM address

- Enabled the CEA extension block, and enabled/disabled the basic audio setting

- Used an exact copy of the 128 byte EDID of my external monitor, with and without 128 bytes of padding

 

What are some other things that I can try? Besides the EDID, what else can be causing this issue?

[hamster]

Hi,

A bit of background....

The transmitter uses the EDID ROM in the receiver (eg monitor or FPGA board) to see what formats the device can receive.

If it identifies as DVI-D, then the source can only support picture data.

IIfit identifies as HDMI then it can support pictures and audio.

Here is what I think is going on. 

If you plug in the audio extractor by itself (or without the design running in the FPGA, the audio extractor says it supports HDMI, so audio is sent.

When the FPGA design is loaded the splitter passes through the capabilities of the FPGA design in gn, which only supports DVI. So you get picture but no audio.

The solution would be to have a full HDMI receiver in the FPGA (and then you might not require the audio splitter anyway.