Enabling Single Webcam for Multiple Applications Access in Linux

A webcam can not be accessed by two or more applications simultaneously. The solution is you can duplicate the video stream and make it available for any application. In short, you create virtual webcam.
First, a webcam is commonly detected on /dev/video*. Before you go through the steps to duplicate video stream, you should check whether your webcam is working. You can try to capture video using VLC by this command. (For example, your webcam is on /dev/video0)

$ vlc v4l2:///dev/video0

If it doesn't work, you can try to change its mode to 0777 and make sure there's no other applications accessing it. If it still doesn't work, you can buy a new webcam. Seriously. Don't buy cheap and unknown-brand webcam. I have $5 webcam and it had wasted my time.

$ apt-get install ffmpeg linux-generic v4l2loopback-dkms

FFmpeg is main application that will access your webcam and duplicate its video stream. V4L2loopback is needed to create multiple virtual capture devices (loopback devices) in Linux which is used by FFmpeg to store duplicated video stream and accessed by other applications. For example, I want to enable two loopback devices. The new devices will be available on /dev/video* in a sequence.

$ modprobe v4l2loopback devices=2

Then, you can duplicate your webcam.

$ ffmpeg -f v4l2 -i /dev/video0 -f v4l2 /dev/video1 -f v4l2 /dev/video2

Or, you can also set the video resolution.

$ ffmpeg -f video4linux2 -s 800x600 -i /dev/video0 -codec copy -f v4l2 /dev/video1 -codec copy -f v4l2 /dev/video2

After you don't need the loopback devices, you can remove it.

$ modprobe -r v4l2loopback

If there any question or suggestion about this article, just leave it at comment field below. If you think this article is usefull, please share it with your colleagues.

Comments

Rangkaian Sensor Infrared dengan Photo Dioda

Keunggulan photodioda dibandingkan LDR adalah photodioda lebih tidak rentan terhadap noise karena hanya menerima sinar infrared, sedangkan LDR menerima seluruh cahaya yang ada termasuk infrared.
Rangkaian yang akan kita gunakan adalah seperti gambar di bawah ini.

Pada saat intensitas Infrared yang diterima Photodiode besar maka tahanan Photodiode menjadi kecil, sedangkan jika intensitas Infrared yang diterima Photodiode kecil maka tahanan yang dimiliki photodiode besar.
Jika tahanan photodiode kecil maka tegangan V- akan kecil. Misal tahanan photodiode mengecil menjadi 10kOhm. Maka dengan teorema pembagi tegangan:
V- = Rrx/(Rrx + R2) x Vcc V- = 10 / (10+10) x Vcc V- = (1/2) x 5 Volt V- = 2.5 Volt
Sedangkan jika tahanan photodiode besar maka tegangan V- akan besar (mendekati nilai Vcc). Misal tahanan photodiode menjadi 150kOhm. Maka dengan teorema pembagi tegangan:
V- = Rrx/(Rrx + R2) x Vcc V- = 150 / (150+10) x Vcc V- = (150/160) x 5 Volt V- = 4.7 Volt
Sekarang kita akan melihat trimp…

Sariawan dan Vitamin B12

Beberapa hari yang lalu, saya yang kebetulan sedang sariawan diminta teman saya di FKG Unpad yang sedang mencari pasien sariawan, untuk datang ke tempat praktek FKG yang berada di Sekeloa (dekat Dipati Ukur). Awalnya sempat malas, tapi karena saat itu saya sedang tidak ada kerjaan dan FKG tampaknya cukup 'menarik', akhirnya saya memutuskan pergi ke sana. Saya mendaftar jadi pasien di rumah sakit FKG terlebih dahulu, kemudian baru saya diajak ke tempat prakteknya. Saat ditanya apa penyebab sariawan saya, saya tidak ingat. Mulut saya pun kemudian diperiksa. Kaca mulut, sonde, pinset, dll sudah masuk ke mulut saya. Beberapa kali seriawan saya tersentuh. Seorang temannya Gema membantu mencatat data hasil pemeriksaan. Setelah itu, giliran dosennya yang memeriksa mulut saya. Pada bagian akhir sariawan saya diberi suatu obat cair. Pesan dari teman saya untuk memperbanyak minum air dan konsumsi vitamin B12.
Menurut Dosen Gizi dari Departemen Gizi Masyarakat Sumber Daya dan Keluarga, …

Beli Bahan Tekstil dan Jasa Jahit di Bandung

Acara wisuda akan dilaksanakan pada Juli 2012 dan untuk acara tersebut saya memerlukan jas. Saya langsung googling untuk mencari tempat yang menjual jas. Sebelumnya saya sempat berpikir untuk menyewa jas saja namun karena tampaknya jas akan cukup penting nantinya dan harga penyewaan yang umumnya tidak murah maka saya memutuskan membeli. Saya mencari tempat yang menjual jas yang murah di Bandung. Hasilnya beberapa artikel menyebutkan Pasar Baru Bandung menjual berbagai bahan tekstil dan pakaian termasuk jas. Saya langsung membuka Google Maps dan mencari lokasi Pasar Baru Bandung. Berikut adalah lokasi Pasar Baru Bandung.

View Pasar Baru Bandung in a larger map

Setelah mengetahui lokasi tersebut, saya memutuskan pergi sendiri ke Pasar Baru Bandung. Tidak lupa saya menyiapkan GPS berhubung sangat lemah soal arah jalan. Alhasil, setelah sampai di dekat jembatan, sebelum jalan Suniaraja saya sempat mengambil arah yang salah dan akhirnya berputar-putar di daerah sekitar Pasar Baru (Jalan St…

Raspberry Pi Bluetooth Connection

Raspberry Pi 3 provides built-in bluetooh module. Latest Raspbian has been bundled with tools for enabling bluetooth connection. Bluetooth icon will be showed up on top right corner of the desktop. It's a tool to discover available bluetooth devices and connect Pi with bluetooth devices. It is easy to connect any bluetooth-enabled electronic device with Pi. But, sometimes Pi will fail to make a connection especially for bluetooth device which has no standarized services.

From terminal, we can use bluetoothctl tool to scan and connect with a bluetooth device. You should make sure that BlueZ protocol stack has been installed by running $ apt-get install bluez
Run bluetoothctl to enter the tool command windowTurn the power on by running power on(Optional) You can set AutoEnable=true in /etc/bluetooth/main.conf if you want to make the bluetooth auto power-on after reboot.Run devices to see which devices have been pairedRun scan on if your desired device has not paired yet.Run agent o…

My Review for Free Project Management Tools

For about a year I had used Trello as my team project management tool. It helps my team to maintain our "to do" lists. But after increasing of project numbers, as operation manager, I feel hard to maintain each of team jobs on some projects. Some tasks become untouched. After a meeting, our team realize that what team need is clear detail about "What should I do today?" or "What should my teammates do today?". We need find another project management tool. Trello uses Kanban scheme which is very adaptive. I feel it's not suitable for my team which consist of some people with different level of expertise and work on multiple projects. We need tool which is better for more prescriptive process to maintain our projects. Other features of project management tool that we need are free, simple, secure, fast, and has mobile support. First, I search on Google for "Best Free Project Management Tool". After that I decided to try four free tools, they …

How To Use Git in Netbeans

Git is a popular version control application nowadays. Recently I have created a note about its differences with SVN and how to use it in Eclipse. There are many Git client tools. But I just want to show how to use Netbeans built in Git tools. It makes development process easier because it has been integrated with the IDE.
Create Remote Git Repository We need remote Git repository so everyone can store or receive any revision or updated files through the networks. We can setup our own Git server or use public Git server like Github. In this note, I use Github. 1. Create an account in Github and create an empty Git repository
2. Get the remote repository link
Create a New Project in Netbeans and Create Local Git Repository After we have a remote Git repository, we can create a project which will be stored to remote repository. We also need to create local repository before we can push any revision and files to remote repository. 1. Create a project. For example, I create PHP Application…

LUKI NOTES

Search This Blog