On Tue, Jun 20, 2023 at 10:40:31AM -0400, James Knott wrote:
Is this documented anywhere? Sure the audio is sent over the cable, but why should there be such a thing as a blanking interval on a digital system? The blanking interval was used to sync the camera and TV. There is absolutely no need for that with a digital signal. Of course there is a sync method with digital, but that could be contained in the data. When you have a digital signal, multiplexing of different data, including sync, is trivial.
Well HDMI has the audio and video multiplexed in the same signal. HDMI 2.0 and older used 3 data links plus 1 clock link, while HDMI 2.1 uses 4 data links with embedded clocking at up to 12Gbps per link. https://www.fpga4fun.com/files/HDMI_Demystified_rev_1_02.pdf gives a nice explanation of how it worked in HDMI 1.3. 2.1 just got rid of the dedicated clock to free up a 4th signal pair. That was supposed to be a dual link HDMI B connector with 6 pairs instead of 3 but it seems to have never been used.
Read about Real Time Protocol for info on how this is done for audio and video over IP. https://en.wikipedia.org/wiki/Real-time_Transport_Protocol
Sure but HDMI and compressed video of IP have nothing in common really. Vastly different bandwidths and purposes.
I have Rogers IPTV. The TV comes over IP via the cable. That would most certainly be compressed, as was the digital TV I had before it. There are HDMI cables between the Rogers box and my A/V receiver and from the receiver to my TV. Are those cables carrying uncompressed video? I doubt it, considering the signal Rogers distributes originated with ATSC from the broadcasters.
Absolutely it is uncompressed over HDMI. The signal from rogers is compressed and encrypted and the rogers box decodes that and send out the raw video over HDMI (with HDCP protection of course). This is why HDMI is carrying 10.8Gbps or 18Gbps or even 48Gbps for the latest standard. Uncompressed video is huge. -- Len Sorensen