Live data from Hacker News

Sending audio to LKV373 HDMI extenders (2021)

eta.st

11–20 of 31 posts

Re: Sending audio to LKV373 HDMI extenders (2021)

#11
post #5
post #4

I didn't even know HDMI extenders over IP existed! I wouldn't use it for TV/movies, because the re-compressed picture can't look all that great. But I could imagine plenty of uses for something like that!

Why do you assume the signal is being recompressed or in any other way manipulating the image?

You can look at the protocol analysis in the post to see that it's sending MJPEG

Re: Sending audio to LKV373 HDMI extenders (2021)

#12
post #9
post #7

Earlier quoted context omitted.

Well, for one, the fact that it's streaming frames as motion JPEG...

Where do you see that? I quickly glanced at the Amazon listing, and saw nothing about this. I could have glanced too quickly and missed it, but it just seems like a totally strange thing for it to do.

It’s in the article

Re: Sending audio to LKV373 HDMI extenders (2021)

#13
post #6

Earlier quoted context omitted.

Because a 1080p60 video stream is about 3Gb/sec on the wire uncompressed like happens over HDMI. 1920w * 1080h * 3colorbytes * 8bits/byte * 60fps = 2,985,984,000 bits/sec.

Okay, but the original signal is not RAW uncompressed either. It's just a serial signal, so converting that into IP packets is pretty much all I'm assuming this is doing and then converting those back to an HDMI formatted signal on the other end. The only thing different about this unit from others is that it's actually turning them into actual network traffic to connect to an existing network.

> Okay, but the original signal is not RAW uncompressed either.

HDMI is in fact the RAW color values, uncompressed. Each of the color channels are serial, but that doesn't really change anything about the raw bitrate.

Re: Sending audio to LKV373 HDMI extenders (2021)

#14
post #6
post #5

Earlier quoted context omitted.

Why do you assume the signal is being recompressed or in any other way manipulating the image?

Because a 1080p60 video stream is about 3Gb/sec on the wire uncompressed like happens over HDMI. 1920w * 1080h * 3colorbytes * 8bits/byte * 60fps = 2,985,984,000 bits/sec.

Much closer to 5 Gbps when you factor in horizontal/vertical blanking + TMDS 8b10b encoding.

Re: Sending audio to LKV373 HDMI extenders (2021)

#15
post #6

Earlier quoted context omitted.

Because a 1080p60 video stream is about 3Gb/sec on the wire uncompressed like happens over HDMI. 1920w * 1080h * 3colorbytes * 8bits/byte * 60fps = 2,985,984,000 bits/sec.

Much closer to 5 Gbps when you factor in horizontal/vertical blanking + TMDS 8b10b encoding.

For sure, I'd simply expect even a simple non-compresing bridge to strip a lot of the 'dead air' and expansion at the physical layer. Just wanted to show that even best case of simply the color value bits leaves you with ten pounds of potatoes to fit into a five pound bag.

Re: Sending audio to LKV373 HDMI extenders (2021)

#16
post #6

Earlier quoted context omitted.

Because a 1080p60 video stream is about 3Gb/sec on the wire uncompressed like happens over HDMI. 1920w * 1080h * 3colorbytes * 8bits/byte * 60fps = 2,985,984,000 bits/sec.

Much closer to 5 Gbps when you factor in horizontal/vertical blanking + TMDS 8b10b encoding.

That’s very doable on a 10gb Ethernet network which is becoming more and more normal.

Re: Sending audio to LKV373 HDMI extenders (2021)

#17
post #16

Earlier quoted context omitted.

Much closer to 5 Gbps when you factor in horizontal/vertical blanking + TMDS 8b10b encoding.

That’s very doable on a 10gb Ethernet network which is becoming more and more normal.

It's going to be a while before 10Gb ethernet is available on devices that cost ~$30/pair.

Re: Sending audio to LKV373 HDMI extenders (2021)

#18
post #16

Earlier quoted context omitted.

Much closer to 5 Gbps when you factor in horizontal/vertical blanking + TMDS 8b10b encoding.

That’s very doable on a 10gb Ethernet network which is becoming more and more normal.

Irrelevant. The hardware under scrutiny is a chinesium HDMI over IP extender with 1 Gbps Ethernet PHY at best.

Re: Sending audio to LKV373 HDMI extenders (2021)

#19

Earlier quoted context omitted.

Okay, but the original signal is not RAW uncompressed either. It's just a serial signal, so converting that into IP packets is pretty much all I'm assuming this is doing and then converting those back to an HDMI formatted signal on the other end. The only thing different about this unit from others is that it's actually turning them into actual network traffic to connect to an existing network.

> Okay, but the original signal is not RAW uncompressed either. HDMI is in fact the RAW color values, uncompressed. Each of the color channels are serial, but that doesn't really change anything about the raw bitrate.

I suspect that just delta compression would reduce the required number of bits considerably.

Re: Sending audio to LKV373 HDMI extenders (2021)

#20

Earlier quoted context omitted.

Okay, but the original signal is not RAW uncompressed either. It's just a serial signal, so converting that into IP packets is pretty much all I'm assuming this is doing and then converting those back to an HDMI formatted signal on the other end. The only thing different about this unit from others is that it's actually turning them into actual network traffic to connect to an existing network.

> Okay, but the original signal is not RAW uncompressed either. HDMI is in fact the RAW color values, uncompressed. Each of the color channels are serial, but that doesn't really change anything about the raw bitrate.

Just to throw a little more hair-splitting, we're not talking about raw data, either, raw being a term of art for unprocessed or minimally processed data read from a device (like an image sensor). It usually can't be displayed without some interpreting.

HDMI video signal is uncompressed but not raw.

Post reply on HN