A real home online cinema on a TV set-top box with Android. Cinema/surround 5.1 DIY project

We then decided that we would build a cinema at home. A TV is not suitable for this; we need a projector.

I chose FORMOVE FengMi S5. This is the Chinese version and the original craftsmen and craftsmen of the seller have harshly replaced the launcher, stuck alternative programs into it that are conditionally working. Therefore, I decided to use it only as a projector with an HDMI input. This part of this device works flawlessly. Autofocus at a distance of 4.5 meters to the screen works great, the diagonal turned out to be about 160 inches, in the settings I reduced it to 150. More than enough for a home theater. The brightness is such that comfortable viewing during the day in cloudy weather is possible.

The solution is not simple. Raspberry Pi 4 with sound via the I2S interface as in a DSP machine, in principle, cannot reproduce multi-channel sound. The Broadcom BCM2712 processor on which the Raspberry Pi5 is built has this capability, but it has not yet been implemented. This was reported by programmers from the Raspberry Pi Foundation, I know them well since we together integrated the ChipDipDAC driver and overlay into the official Raspberry Pi OS. You can, of course, output sound via USB audio, where the Raspberry Pi can get Surround 5.1. But if it’s USB audio, then it’s better to use a TV set-top box on Android, at least it will be cheaper. Android has a very well developed USB audio output and you can get multi-channel sound of very high quality.

For USB transport I will only use Reflex3 due to its incredible flexibility in sound settings. And because I am one of the developers of Reflex transports. Reflex itself is only a USB/I2S transport and therefore, to output analog multi-channel audio, it is installed on our (Chip and Dip) single-board audio computer “Audio Artwork 1452-1934-1761”

Selecting an online cinema and TV set-top box.

Choosing an online cinema with surround sound was the most time-consuming task. Currently (and this is October 2024), films with a 5.1 track can be viewed on Kinopoisk, Ivy, Okko, Wink and Netflix. These are the theaters that I have made subscriptions to and tested the 5.1 surround sound from the apps. Maybe there are others.

I simultaneously tested this on several TV boxes with Android TV and Google TV.

It worked like this. When connecting the Reflex with settings for 5.1 audio output, all applications determined that it was possible to output audio in 5.1 format, but the audio was output in this format only on those set-top boxes that had a Dolby audio license. If the set-top box does not have this license, then it is simple stereo. But it’s not so simple there either. Let's go through online cinema applications.

1. OKKO. On TV boxes with a Dolby audio license, the player offers to output sound in 5.1 format, but there is NO sound via USB audio. It is not possible to switch to stereo mode. On TV boxes without a Dolby audio license, the sound is output in stereo and works great, but I don’t need it. Support promised to fix this. I'm waiting for the update.

2. Kinopoisk. On TV boxes with a Dolby audio license, the player offers to output sound in 5.1 format, but there is NO audio sound via USB either. But there is a choice of Stereo audio track. Everything is fine there, but not necessary. On TV boxes without a Dolby audio license, the sound is output immediately and only in stereo.

3. Netflix. The same as in Kinopoisk. There is no sound when selecting a 5.1 track. Stereo is fine.

4. IVI. Everything is generally good there. On set-top boxes with a Dolby audio license, the sound on 5.1 tracks is excellent, but it starts with stereo and switches to surround after 5-6 seconds. On the stereo tracks everything is fine. Okay, but there's also Wink.

5. Wink. Flawless playback of 5.1 tracks via USB audio. No delays, excellent quality. Dynamics, scene. When the helicopter flies, the children hide behind the seats. And if there is a cartoon battle scene, they run to the aid of the heroes. Full immersion!

My choice is Wink and IVI and TV set-top box media player Xiaomi mi box s 2nd gen, it has a Dolby audio license.

Technique.

Now low level for DIY practitioners.

USB-I2S transport Reflex 3 is set to “Audio Artwork 1452-1934-1761”. We will use “Artwork Control Panel Disp”, it has a sample rate / bit depth indicator, volume control and mode switch. There are two more buttons and indicators on addressable LEDs. How to combine all this into a cinema? On “Audio Artwork 1452-1934-1761” there are four scarves with opamps attached. Power supply 12V/0.5A.

The picture shows the assembly of a cinema.

Particular attention to jumpers. Marked with red rectangles.

Outputs/inputs are labeled as in SigmaStudio.

BY.

The “Audio Artwork 1452-1934-1761” board has DSP ADAU1452 and DAC AD1934 installed, so the cinema project will be created using SigmaStudio, and with the help of ChipStudio it will be transferred to control and configure the cinema in the Reflex transport.

SigmaStudio

It is a graphical interface for controlling and configuring various digital audio processors manufactured by Analog Devices. In SigmaStudio you can build an audio path of almost any configuration, connecting various sound control algorithms. In our case, the ADAU1452 audio processor and AD1934 DAC are configured as a 6-channel audio path (5.1). Six audio channels from the Reflex transport, already laid out in 5.1, are fed to the preset switch, what should I call it correctly? presets, or something. What does it mean? In the top position, six channels are sent to six outputs via a master volume control. There is no special processing. Only on the subwoofer channel there is a super-bass algorithm and on the central channel a filter with a high-frequency shelf from 6 kHz with a low quality factor and a slight gain of +3 dB. Adds transparency to the scene. The super bass is set to 40Hz with an intensity factor of 1.3 and a gain of 1.2 (the emotional impact of turning this algorithm on is very high, be careful). The SuperBass algorithm does not boost the bass level, but artificially generates high harmonics above the crossover frequency, creating the impression of increased bass. Intensity sets the level of these harmonics, and gain is applied to the signal below the tuning frequency (40Hz in our case).

The lower three positions of the “preset” switch enable ADIsurround algorithms, which decode the stereo input signal into surround sound. This is turned on if there are no surround channels at the cinema input, but only stereo. As a result of the decoding process, we obtain a channel from the sum of the left and right channels, (L+R), which contains frontal information, and a difference channel (the difference between the left and right channels, LR / RL), which contains information about the environment. Depending on the mixing and distribution of the difference channel with the sum channel, left, right, center, side or rear surround channels are obtained. Front L and R speakers deliver music, front-facing sound effects and directional dialogue; The center speaker carries most of the dialogue, while the surround speakers (ideally positioned to the side of the listeners and slightly above them) provide ambience and surround effects. I switch three algorithms: Club, Cinema and Rock.

Open the project in SigmaStudio, everything is much clearer there. You can view and check/change various settings for a hall or small room. You can experiment with them to tailor the sound to the room the system is in and personal preferences. But be aware that there is no “correct” setting for ADISurround algorithms.

ChipStudio

SigmaStudio's interface is a powerful program. All changes and settings for the correct (your) sound can be done on the fly by connecting to the DSP via the I2C or SPI interface. It's free, which is important. But there is one drawback for users without DSP programming experience. SigmaStudio does everything only if it is running on a PC. When you disconnect DSP from SigmaStudio, the project stops and the DSP as an independent device does not work. To transfer the project to a microcontroller, for example installed on Reflex, the ChipStudio environment was created. This is also a graphical interface that understands the saved SigmaStudio file and, when connected via USB to the Reflex transport, correctly transfers the project into memory for offline operation. In the project file you will find the so-called combo project for the cinema. ChipStudio is also a free program. Open the cinema combo project in it, connect Reflex in download mode and transfer it to memory. Now Reflex will control the ADU1452 DSP and AD1934 DAC connected via SPI interfaces. All adjustments from this project placed on the control panel are connected to GPIO Reflex.

This is what the project looks like in ChipStudio

This article is just a guide. I just want to bring your attention to some amazing projects in digital audio management. If you download SigmaStudio and look at its capabilities, you will simply be shocked: Well, how did they (AD) come up with all this? Such complex processes and such simple controls. And if you get to practice and open ChipStudio, I will be simply happy.

Make a real home theater yourself, stock up on popcorn! Relax!

Instructions for SigmaStudio – ADI Algorithms [Analog Devices Wiki]

Instructions for ChipStudio, the program itself in the Technical documentation section – Reflex 3.0, USB Hi-Res transport PCM up to 32bit/384kHz, DSD512, SPDIF Out 384kHz, Surround 4xI2S, TDM

Sigma Studio and ChipStudio projects for cinema in archive.