[HN Gopher] Sending audio to LKV373 HDMI extenders ___________________________________________________________________ Sending audio to LKV373 HDMI extenders Author : luu Score : 57 points Date : 2023-07-03 00:19 UTC (22 hours ago) (HTM) web link (eta.st) (TXT) w3m dump (eta.st) | squarefoot wrote: | There was some effort to reverse engineer those devices [1] so | that one could use for example either transmitters or receivers | paired with normal PCs and not just connecting them straight each | other. There are also newer models around, though I'm not aware | of any reverse engineering efforts so far. | | If you want to tinker with them, please leave some writeup of the | results. Beware that there are both HDMI over IP and | aesthetically very similar, but often cheaper, HDMI over Ethernet | cable adapters. The 2nd ones contain no brain and can't do any IP | encapsulation, they're essentially just level translators using | CATx cable to carry the HDMI signals, and of course aren't | compatible with any network devices, switches, etc. For that use, | you want HDMI to IP transmitters and receivers, which should be | clearly marked as capable of working in a network environment. | Check carefully the features before buying, because some among | the stupid level translators sold on the usual channels are | marked as HDMI over IP, which they clearly are not. | | 1 - https://blog.danman.eu/reverse-engineering-lenkeng-hdmi- | over... | rektide wrote: | People are amazing. I love this. Adore it. A thread of various | awesome enterprising hackers, searching for truth, and using | observability & tools to uncover meaning. Then bend reality to | their whims & desires. This is the best human spirit. It's a pity | technology so often obstructs rather than builds this human | mastery. Alas! Never-the-less, humanity persisted. Against the | throws of corporate-controlled limiting tech. Break out that | wireshark & conquer in the name of freedom! Become great! Be | unbounded. | | I have huge respect for the Chromecast ecosystem, but there's so | many weird prickly points for it. For a while I had a chromecast | plugged in to a computer which then variously resent the output. | This looks like a great way to do the same but simpler/dumber. | One of the specific flaws of Chromecast is that if you stream a | video, it can only go to a single device. Meaning my whole home | audio does no good. Something like this could help me work-around | that limitation. It's great how absurdly flexible these devices | are, but it sucks enormous egg that Chromecast apps will only | stream in the first place to signed Chromecast devices; this | whole thing should be a non-issue I can software workaround. But | a hardware workaround like this is adequate. | awehoiwaegw wrote: | [dead] | jaywalk wrote: | 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! | bobsmooth wrote: | You can do HDMI over a lot of things. They all work by encoding | the video stream, usually h264, and sending it over the | network. Check out HDBaseT which does video, ethernet, USB and | power over a single cat5e cable. | dylan604 wrote: | Why do you assume the signal is being recompressed or in any | other way manipulating the image? | belthesar wrote: | You can look at the protocol analysis in the post to see that | it's sending MJPEG | monocasa wrote: | 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. | dylan604 wrote: | 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. | monocasa wrote: | > 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. | jacquesm wrote: | I suspect that just delta compression would reduce the | required number of bits considerably. | duskwuff wrote: | Lossless compression isn't a good fit for real-time | video. Being able to get some compression ratio on a | "typical" image means your stream will drop out when the | user has an image on screen which doesn't compress well. | Clamchop wrote: | 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. | metaphor wrote: | Much closer to 5 Gbps when you factor in | horizontal/vertical blanking + TMDS 8b10b encoding. | monocasa wrote: | 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. | mnd999 wrote: | That's very doable on a 10gb Ethernet network which is | becoming more and more normal. | monocasa wrote: | It's going to be a while before 10Gb ethernet is | available on devices that cost ~$30/pair. | toast0 wrote: | You're right, but used dual port 10g ethernet cards do go | for about $30/each... Of course, that doesn't get you | hdmi encode/decode, and not new. | metaphor wrote: | Irrelevant. The hardware under scrutiny is a chinesium | HDMI over IP extender with 1 Gbps Ethernet PHY at best. | duskwuff wrote: | Well, for one, the fact that it's streaming frames as motion | JPEG... | dylan604 wrote: | 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. | mrpippy wrote: | It's in the article ___________________________________________________________________ (page generated 2023-07-03 23:01 UTC)