Audio, Not Video Over The LKV373 HDMI Extender

August 2, 2023 by Matthew Carlson 11 Comments

[eta] found herself in a flat with several LKV373 HDMI extenders. Find the corresponding transmitter, plug it into your device, and you’ve got a connection to the TV/sound system, no fussing with wires behind the TV. However, [eta] wanted to get rid of the need to plug in a laptop and start sending packets directly to play music. As her flatmate [dan] had already reverse-engineered the receiver, she tested her prototype against their virtualized receiver, de-ip-hmdi.

The actual sending of images was surprisingly straightforward — just a JPEG sliced into 1024 bytes chunks and sent over. However, early testing showed nothing on the receiver. The end of a frame needed marking by setting the most-significant bit of the chunk number to one. Now de-ip-hdmi showed the image, but the actual hardware would not. With something missing, [eta] returned to Wireshark to scan packets. Noticing some strange packets on port 2067, she analyzed the pattern to reveal it sent another packet just before a new frame and included the frame number. With this tweak, it was still not enough. Ultimately, heartbeat packets sent every second synchronize things, but compared to the noise of the video packets, they were easy to miss. Now [eta] had some functioning video streaming rust code.

In theory, audio for the LKV373 followed the same thought process as video. Two channels of 32-bit big Endian integers at 44,100 hz chunked into 992-byte sections and sent as a packet formed the audio stream. With only 992 bytes, two streams, and 4 bytes per sample, each packet only held 2.812 milliseconds of sound. The first tests resulted in no audio output or distorted crunchy sound. Of course, this was every audio engineer’s worst nightmare: jitter. With a spin loop and an efficient ring buffer, the audio packets were soon slinging across the network reliably.

The code is available on a hosted version of GitLab. It’s a beautiful journey through reverse engineering some obscure but relatively cheap hardware. Along the way, there is nicely annotated Rust code, which makes it all the better.

Tivoli Teardown Disappoints

July 25, 2023 by Chris Lott 32 Comments

[Fran] has been curious about the innards of Tivoli Audio’s Model One radio, but was reluctant to shell out $200 just to tear it apart. But she found one recently on eBay, won the auction, and proceeded to do a review and teardown. Spoiler alert, she was disappointed.

Physically speaking, the radio looks great and has quite an array of I/O connections. The geared tuning knob looks cool, but is heavily damped which [Fran] isn’t keen about. Turning it on, a few more quirks are discovered. The volume control is out-of-whack — it appears they substituted a linear taper potentiometer where a logarithmic taper was called for.

Another problem, at least in the RF-dense metropolitan areas like Philadelphia, is the FM tuner’s station-lock feature. It is so strong that it can be impossible to tune in weak stations. This is especially ironic since, according to Wikipedia, that was one of audio engineer Henry Kloss’s main goals when founding Tivoli Audio back in 2000:

Their first product was the Model One, a simple to use mid-century modern designed table top radio with a high-performance tuner, receiving FM radio in congested urban locations, while maintaining the ability to pick out distant or low power stations. Kloss had noted that the mid 60’s wave of Japanese radios lacked the ability to receive FM stations in congested locations, and this became a defining goal of his radio designs throughout his career.

Interestingly, many folks in the YouTube comments say their Model One radios have none of these issues. We wonder if [Fran] has obtained a damaged radio, or maybe a newer version produced with less attention to detail. If you have a broken Model One radio, before tossing it, consider the hack we wrote about last year, turning it into an internet radio.

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Hackaday Prize 2023: OMOTE Universal Remote

July 15, 2023 by Tom Nardi 39 Comments

A good universal remote can help tame today’s complex home entertainment systems, combining both classic IR and more modern WiFi and Bluetooth connectivity with programmable functions that allow the user to execute multi-step operations with a single button. Unfortunately, programming them often involves the use of clunky proprietary software.

Which is why [Maximilian Kern] has developed the OMOTE. This open source universal remote is powered by the ESP32, and features the usual collection of physical buttons in addition to a 2.8” 320 x 240 touchscreen with a responsive graphical interface that can display more advanced user interfaces. Everything is packed into an ergonomic 3D printed case that gives it an exceptionally professional look.

The remote’s USB-C port can be used to recharge the internal 2,000 mAhA battery, as well as reprogram the ESP32’s firmware via a CH340C serial chip. The battery life is estimated to be about six months given the considerable low-power capabilities of the ESP32, which includes the use of a LIS3DH 3-axis accelerometer to keep the hardware in sleep mode until it’s picked up.

The software side is still in development, so the IR codes for the remote are currently hardcoded and its WiFi capabilities are limited to MQTT. But in the future, [Maximilian] imagines a web-based configuration interface that runs on the ESP32 and lets you add codes and setup the remote via your phone or desktop.

It looks like the hardware is more or less complete, so presumably the focus from here on out will be bringing the software across the finish line. Don’t worry, there’s still plenty of time — since it’s an entry into the Gearing Up challenge of the 2023 Hackaday Prize, the judges won’t pick the finalists until August 8th.

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Recreating The Golden Era Of Cable TV

July 13, 2023 by Bryan Cockfield 55 Comments

Fewer and fewer people have cable TV subscriptions these days, due to a combination of poor business practices by cable companies and the availability of alternatives to cable such as various streaming platforms. But before the rise of the Internet that enabled these alternatives, there was a short period of time where there were higher-quality channels, not too many commercials, a possibly rose-tinted sense of wonder, and where MTV actually played music. [Irish Craic Party] created this vintage cable TV network to capture this era of television history.

The hardware for this build is a Raspberry Pi driving an LCD display recovered from an old iPad. There’s a custom TV tuner which handles changing the channels and interfaces with an Apple Remote. Audio is sent through old computer speakers, and the case is built from 3D printed parts and some leftover walnut plywood to give it an era-appropriate 80s or early 90s feel. We’ve seen other builds like this before, but where this one really sets itself apart is in the software that handles the (television) programming.

[Irish Craic Party] has gone to great lengths here to recreate the feel of cable TV from decades ago. It has recreations of real channels like HBO, Nickelodeon, and FX including station-appropriate bumpers and commercials. It’s also synchronized to the clock so shows start on the half- or quarter-hour. Cartoons play on Saturday morning, and Nickelodeon switches to Nick-at-Nite in the evenings. There are even channels that switch to playing Christmas movies at the appropriate times, complete with Christmas-themed commercials.

The build even hosts a preview channel, one of the more challenging parts of the build. It continually scrolls through the channels and shows what’s currently playing and what will be showing shortly, complete with a commercial block at the top. For those who were around in the 90s it’s almost a perfect recreation of the experience of watching TV back then. It can even switch to a video game input when tuned to channel 3. There’s almost too much to go into in a short write-up so be sure to check the video after the break.

Thanks to [PCrozier] for the tip!

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An ESP In Your Mini TV

June 28, 2023 by Jenny List 14 Comments

When miniature LCD TVs arrived on the market they were an object of desire, far from the reach of tech-obsessed youngsters. Now in the age of smartphones they’re a historical curiosity, but with the onward march of technology you can have one for not a lot. [Taylor Galbraith] shows us how, with an ESP32 and an LCD we rather like because of its CRT-like rounded corners.

What he’s created is essentially a small media player, but perhaps what makes it of further interest is its migration from a mess of wires on a breadboard to a rather nice PCB. He’s not released the board files at the time of writing, but since the software can all be found in the GitHub repository linked above, we live in hope. On it are not only the ESP and the screen, but also a battery management board, an audio amplifier, and a small speaker. For now it’s a bare board, but we hope he’ll complete it with a neatly designed case for either a pocket player or a retro-styled mini TV. Until then you can see his progress in the videos below the break.

If you’re after more ESP32 media player inspiration, this isn’t the first retro-themed media player we’ve brought you.

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Know Audio: Distortion Part One

June 6, 2023 by Jenny List 28 Comments

If you follow audiophile reviewers, you’ll know that their stock-in trade is a very fancy way of saying absolutely nothing of quantifiable substance about the subject while sounding knowledgeable about imagined differences between devices that are all of superlative quality anyway. If you follow us, we’ll tell you that the only reviews that matter are real-world measurements of audio performance, and blind listening tests. We don’t have to tell you how to listen to music, but perhaps it’s time in our Know Audio series to look at how audio performance is measured.

Before reaching for the bench, it’s first necessary to ask just what we are measuring. What are the properties which matter in an audio chain, or in other words, just what is it that makes an audio device good?

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Prison TV Gets Simple Speaker Mod

April 13, 2023 by Lewin Day 20 Comments

American prisons are strict about television use. Typically they’re only to be used with headphones, and their enclosures need to be transparent so they can’t be used to smuggle goods. ClearTech makes TVs that meet these specifications, and when [Steve Pietras] got his hands on just such a unit, he set about modding it for use in the free world.

Getting into the TV isn’t easy; ClearTech built the units using special security fasteners unlike any we’ve seen before. [Steve] found a way to deal with these, though declines to share his technique in his video. Once inside though, his task is relatively straightforward. He steps through where to install speakers in the TV’s housing, and how to hook them up to the right spots on the main circuit board. With the case closed back up, [Steve] is able to use the TV without headphones, and without the threat of getting shanked by a fellow inmate who really doesn’t want to hear Jeopardy while they’re trying to read.

It’s not every day we get to look at a piece of obscure hardware like this. We’d never seen a prison TV before, and now we feel like experts on the topic. Of course, we’re no strangers to esoterica at Hackaday.

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