The HDMI to VGA converter has to first provide proper EDID content to the HDMI source prior to receiving the desired 640 × 480p signal—or other standard commonly supported by the video source and display. An HDMI Rx usually stores the EDID content internally, handles the hot plug detect line (indicating that a display is connected), and receives, decodes, and interprets incoming video and audio streams.

Since the HDMI stream combines audio, video, and data, the HDMI Rx must also allow readback of auxiliary information such as color space, video standards, and audio mode. Most HDMI receivers adapt to the received stream, automatically converting any color space (YCbCr 4:4:4, YCbCr 4:2:2, RGB 4:4:4) to the RGB 4:4:4 color space required by the video DAC. Automatic color space conversion (CSC) ensures that the correct color space is sent to a backend device.

Once an incoming HDMI stream is processed and decoded to the desired standard, it is output via pixel bus lines to video DACs and audio codecs. The video DACs usually have RGB pixel bus and clock inputs without sync signals. HSYNC and VSYNC signals can be output through the buffer to the VGA output and finally to the monitor or other display.

An HDMI audio stream can carry various standards, such as L-PCM, DSD, DST, DTS, high-bit-rate audio, AC3, and other compressed bit streams. Most HDMI receivers do not have a problem extracting any audio standard, but the further processing might. Depending on the backend device, it may be preferable to use a simple standard rather than a complex one to allow easy conversion to the analog output for speakers. HDMI specifications ensure that all devices support at least 32 kHz, 44.1 kHz, and 48 kHz LPCM.

It is, thus, important to produce EDID that matches both the audio capability of the HDMI2VGA converter that extracts the audio and the original capabilities of the VGA display. This can be done by using a simple algorithm that retrieves EDID content from the VGA display via DDC lines. The readback data should be parsed and verified to ensure that the monitor does not allow higher frequencies than those supported by the HDMI Rx or video DAC (refer to Table 4). An EDID image can be extended with an additional CEA block that lists audio capabilities to reflect that the HDMI2VGA converter supports audio only in its linear PCM standard. The prepared EDID data containing all the blocks can, therefore, be provided to the HDMI source. The HDMI source should reread EDID from the converter after pulsing the hot plug detect line (part of the HDMI cabling).

Available in the market within $5.