[GTALUG] CVT-RB: another video mystery

[James Knott]

On 2023-06-20 09:23, Lennart Sorensen wrote:
> Supposedly HDMI is using some of the blanking space to send audio,
> so I guess it has some use.

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.

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

> HDMI is sending uncompressed frames

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.