Voodoo Business

Combine video and audio (yt-dlp)

First of all, after using yt-dlp to download 2 webm files for a video, you can combine them without reencoding using the following command (See here), Just make sure both files are VP8 or VP9

ffmpeg -i ao.webm -i vo.webm -c:v copy -c:a copy output.webm

Extract segment from video

To extract the section from the file resulting from the first command above

1- From second x, and duration in seconds

ffmpeg -ss 285 -i g_in.mkv -t 5475 -map 0 -c copy g_out.mkv

2- From second x to second y

ffmpeg -copyts -ss 4633 -i g_in.mkv -to 5470 -map 0 -c copy g_p2.mkv

Convert file

Converting a file you have downloaded using 1 or any other file into MP4 (H264), since some windows computers will not play a webm file !

ffmpeg -i source264.mp4 -c:v libx265 -crf 28 -preset fast -c:a aac -b:a 128k  -filter:v fps=25 out265.mp4

If you want to cut a part of the video, without re-encoding it

ffmpeg -i input.mp4 -vcodec copy -acodec copy -ss 00:01:00.000 -t 00:00:02.000 output.mp4

nVidia (GPU) : Convert H264/H265

Nvidia graphics card to convert H265 (MKV) to H264 MP4, Using nvidia hardware encoder to encode video into H264 or H265 !

To checks whether hardware encoders are available or not, run the command

ffmpeg -encoders | findstr /ic:"NVIDIA"

If the following two lines are in the command, you can use the nVidia encoder, the first codec is H264, and the second is for H265 (HEVC)

V....D h264_nvenc           NVIDIA NVENC H.264 encoder (codec h264)
V....D hevc_nvenc           NVIDIA NVENC hevc encoder (codec hevc)

ffmpeg.exe -vsync 0 -hwaccel cuda -i <input_file> -map 0  -c:a copy -c:v h264_nvenc -pix_fmt yuv420p -preset hq <output_file>

-vsync : Synchronize video audio and metadata using the video timestamp
-hwaccel cuda : Use nVidia’s cuda for hardware accelleration

Example, Convert mkv to mp4 (Tested OK)

Now, with the above out of the way, the following command should encode your 1080P mkv H265 video to H264 ! all within GPU, so this re-encodes an nVidia compatible format to another nVidia compatible format, on my 1650 card, it was encoding at 12x. this provides better compatibility, if smaller file size and quality are what you seek, then you should do it the other way around

ffmpeg -i "1080p.mkv" -c:v h264_nvenc -pix_fmt yuv420p -minrate 500k -maxrate 1000k -c:a mp3 -b:a 128k "1080p.mp4"

The other way around

ffmpeg -i "1080p.mp4" -c:v hevc_nvenc -pix_fmt yuv420p -minrate 200k -maxrate 1000k -c:a aac -b:a 128k "1080p.mkv"

NOTE: The above does everything within the GPU, if for example you wanted the decoding on CPU, that will make things much slower because the decoded video (Huge) will still need to be copied to the GPU,

nVidia : DVD to H265

Now one very common task people want to execute is converting their old, bulky DVD collection to H265 (Or H264 if they value compatibility over size and clarity), DVD files are usually on a DVD in the Video_TS folder, and the AudioTS folder, So this will create a few cases

Case 1: Audio_ts folder is empty, Video TS folder has files that you know the order they should be displayed in, the objective is to put them all in one video file (Assuming MKV but the container is your choice), in this case, I usually start by converting all the videos to H265, then combine them, here, most of my videos are interlaced (that will be dealt with with yadif), and sometimes, they are files of different resolutions, so I will unify their size

ffmpeg -i "v1.VOB" -c:v hevc_nvenc -c:a aac -b:a 256k -vf yadif,scale=1920:1080 -x265-params "crf=22:min-keyint=25:keyint=50" -preset slow "d1.mkv"

Now, create a list of the files

(for %i in (*.mkv) do @echo file '%i') > mylist.txt

And concatenate the videos

ffmpeg -f concat -i mylist.txt -c copy output.mkv

Now, to batch process a folder on the command line... in this example i am lowering the resolution of files to FHD from 4K

for /f "tokens=1 delims=." %a in ('dir /B *.mp4') do ffmpeg -i "%a.mp4" "%a.1080.mp4"

And here is one meant to extract the audio from all the MP4 files

Windows

for /f "tokens=1 delims=." %a in ('dir /B *.mp4') do ffmpeg -i "%a.mp4" -vn -acodec copy "%a.aac"

Linux

for i in *.mp4; do ffmpeg -i "$i" -vn -acodec copy "${i%.*}.aac"; done

Split audio file

ffmpeg -i 2024-07-27_20_38_2.m4a -f segment -segment_time 1740 output_%03d.m4a

Converting MKV to MP4

Here is a case where my MKV file contains the audio in AAC, and the video in H264, As you slide the slider in VLC media player, it tells you what the section is about, i should be able to copy the streams exactly as they are, but I was concerned that the “Slider Hints” would disappear, hence I split it into audio and video without re-encoding, checked that the hints are still there in the video, then combined them into an MP4, also without encoding, the reason I wanted the container to be MP4 is that sometimes I access my network files in a browser, and browsers seem more comfortable playing MP4 files than MKV

* ffmpeg -i My_Dinner_With_Andre_1981.mkv -vn -acodec copy ao.aac
* ffmpeg -i My_Dinner_With_Andre_1981.mkv -an -c:v copy vo.mp4
* ffmpeg -i ao.aac -i vo.mp4 -c:v copy -c:a copy My_Dinner_With_Andre_1981.mp4

Reload

firewall-cmd --reload

Dealing with zones

* firewall-cmd --get-zones <- Show all zone names
* firewall-cmd --list-all-zones <- Detailed info about all zones
* firewall-cmd --zone=zone-name --list-all <- show everything about a certain zone
* firewall-cmd --get-default-zone <- What is the current default zone
* firewall-cmd --set-default-zone zone-name <- set new default zone
* firewall-cmd --get-active-zones <- List the active zones and the interfaces assigned to them
* firewall-cmd --permanent --zone=public --change-interface=enp1s0 <- connect the public zone to eth0, REQUIERS RELOAD

In this mini tutorial, I will be adding the user kareem to the system, and allow kareem to sftp into a web directory where he can post his web design work, as usual, the steps first, then whatever explanations !

There are two ways to do this, one to add one user, the other to add a group of users, you can either pick one, or do both !

The part in common between both solutions

apt-get install openssh-server
adduser kareem
Then enter a new password twice for kareem

The interesting thing about this sftp user business is that the directory we will specify as the root for the user kareem has to be owned by root ! so go ahead and create the directory /var/www/html/usr/kareem, then execute the following commands

chown root:root /var/www/html/usr
chmod 755 /var/www/html/usr

chown kareem:kareem /var/www/html/usr/kareem

Now, the user kareem owns a directory within his root directory that he can write to, and can not write outside that directory since he does not have the OS permissions, Now, let us add kareem to the list of people who have sftp access but not ssh access.

Edit /etc/ssh/sshd_config and append the following to the document

Match User kareem
ForceCommand internal-sftp
PasswordAuthentication yes
ChrootDirectory /var/www/html/usr
PermitTunnel no
AllowAgentForwarding no
AllowTcpForwarding no
X11Forwarding no

Now, restart the service by executing the following command

systemctl restart ssh

You are done, try connecting with something like winSCP

Besides winSCP, you can also simply mount the linux filesystem where you have permissions on your windows machine, here are the complete instructions on how to do that https://www.qworqs.com/2022/10/09/mounting-a-remote-linux-file-system-as-a-windows-drive/

I haven’t played any games in 20 years, up until early this month, I played a simple game on my phone, nice, but I’m not addicted, no urge to pick up the phone

So, having no windows PC of my own, i decided to install the open source supertuxkart on my debian (gnome) machine

the game is a joke compared to modern day graphics and physics, but it is fun, with things like bombs and banana skins and stuff, i don’t think i will be playing it often, but there you have it

The answer to this should be simple, I initiated the test with

badblocks -nsv /dev/sdb

, first, interrupt bad blocks with ctrl+c, the output should be

Checking for bad blocks in non-destructive read-write mode
From block 0 to 1953514583
Checking for bad blocks (non-destructive read-write test)
Testing with random pattern:   0.92% done, 49:38 elapsed. (0/0/0 errors)
 21.32% done, 18:49:24 elapsed. (0/0/0 errors)

Interrupted at block 416437376

Interrupt caught, cleaning up

Okay, so we know what blocks it was supposed to check (1 through 1953514583), and where it was interrupted (416437376)

So i will ask it to resume testing from where it finished (-1), up to the end

badblocks -nsv /dev/sdb 1953514583 416437375

n = Non destructive
s = Show progress
v = tell us about what you find !

The new run should tell you the percentage correctly, but the time counter will be reset to zero, as it is only counting how long this run has been running for

One thing to note is that bad blocks can be used to instruct the filesystem to avoid the bad blocks, but it also allows the disk’s firmware to substitute bad blocks with spare blocks, so that the disk works again with no intervention from your end !

So for my 2TB hard drive…

416437375 = 21% (13 hours)
619014719 = 31.6% (+23:22)
627995199 = 32.15% (+1:04)
667782398 = 34.18% (+4:46)
715469885 = 36.62% (+5:44)
827834875 = 42.38%

While running the tests, you might want to keep an eye on the hard drive temperature with a command like

hddtemp /dev/sdb

To create a log file of the bad blocks, every run should have it’s own file !

badblocks -nsv -o /root/badblocks3.txt /dev/sdb 1953514583 627995198

The concatenation of those files you are creating is very useful in creating a file system if you ever decide to format the drive later !, but the recommended way is using badblocks with the other disk tools directly

while the test is running, you will see 3 numbers that correspond to readerror/writeerror/corruptionerror

To begin with, the links here are Amazon associate links, what this means is that buying things using those links will result in a commission for me ! to recap. “As an Amazon Associate I earn from qualifying purchases.”

What I am trying to do is to create a cover that allows me to switch between USB OTG devices easily at the workshop, so i created a 3D printed connector that fits with the following parts, the STL for that model will be provided once I use it and make sure it works, In addition to the pixel 6 pro, have made the 3D printed connector holder for the Samsung Galaxy S10, S10+, Ulefone Power 5, Ulefone Armor 3,

The external camera also has a 3D printed case design which I will also share… the screen protector has nothing to do with the project, but i am getting it anyways because it is nice if you have screen protection at the workshop, the screen protection uses UV curing adhesive ! which may or may not ruin your oleophobic coating on your screen (remains to be seen)

Things that I am getting

Screen protector Here said to work best with the fingerprint sensor (Once you use the penny trick), and tough enough to stay put with those curved edges !

2 phone covers here (Shaded Spurce (Green) and Slate (Grey))

4 of USB C Magnetic Adapter here, 2 Elbow and 2 Flat Elbow

Things that I don’t want to buy but are worth mentioning

Google’s Air Buds (Pixel) are on sale for $99 (here) and the pro are discounted at $199 (Here), I personally like my ugreen with qualcom chipset, So i don’t think i will get the google ones any time soon, but they are here for ref.

A couple of hours ago, i received a video that is 50 frames per second, and compressed in H264, the video was 58MB, and she wanted it less than 15 to send it via email, the video was 1:45 long, so i re-encoded it in H-265 but she had a problem playing it (No codec), so i decided to re-encode it with VP9 (webm).

to arrive at a number less than 10, i needed to be encoding at around 1 MegaBIT per second, now, to do this, I made a 2pass encoding with ffmpeg as follows

ffmpeg -i source.mp4 -c:v libvpx-vp9 -b:v 1M -filter:v fps=25 -pass 1 -an -f null /dev/null && \
ffmpeg -i source.mp4 -c:v libvpx-vp9 -b:v 1M -filter:v fps=25 -pass 2 -c:a libopus out.webm

The first pass collects statistics about the source video in a text log file, the second pass encodes the new video, from the options above, i have taken the frame rate to 25fps (from 50), and instead of defining the crf, i simply told ffmpeg what the biterate I need is, which is 1Mbit per second (Every 8 seconds, 1 MBYTE)

The previous one, H-265 was done with the command

ffmpeg -i source264.mp4 -c:v libx265 -crf 28 -preset fast -c:a aac -b:a 128k  -filter:v fps=25 out265.mp4

the H265 was smaller due to the crf factor used, as well as the lower frame rate

Like the name implies, this is a cheat sheet to quickly find the command you need, they are ordered by the frequency a command is used, or at least what i think is going to be needed more frequently, I have also grouped them by function

The container name in the examples is mycontainer, it is just a name that you will need to replace with your own container name, the container ID here is always 12345abcdef

Command	Arguments	What it does
============>	Containers – list
docker container ls		Display running containers
docker container ls -a	a: also show containers that are not running	Display all containers, running or not
docker ps	Show running containers	PS is the same as LS but older
============>	Containers – Run
docker run --name mycontainer -i -t imagename	1- The name of the container to run (mycontainer) 2- The i flag indicating you’d like to open an interactive SSH session to the container. The i flag does not close the SSH session even if the container is not attached. 3- The t flag allocates a pseudo-TTY which much be used to run commands interactively. 4- The base image to create the container from (imagename).	Runs the container, and leaves you on a shell prompt that executes commands on that container (As if you have ssh-ed into it)
docker run --name mycontainer -d imagename	-d for running the container in the background
docker stop my_container		Stop the running container
docker exec -it mycontainer /bin/bash	-it flag allows you to run a container in interactive mode	If this doesn’t work, you may not have bash installed, you can try the next command Gives you access to the shell, much like opening an SSH session to the container
docker exec -it username/mycontainer /bin/sh
ctrl+p followed by ctrl+q		Detach from container

Sometimes, accessing a container throght the command line may not be enough, there is a chance you want to access it for file transfer for example, in that case, you want port 22 exposed, and you want to be connected to it like you would connect to a virtual machine

Superior in both Lossless compression, and Lossy compression, webp is the new image format by google

Already supported by all web browsers *(that i have tested it with), webP is indeed a promising format, so let us get to compressing our images

I have a big bunch of bitmaps that my scanner spits out (To avoid lossy jpeg compression the scanner’s driver produces), and i need them converted to lossless webp to save space (the first image I compressed went from 552MB bitmap to 183), that is 33% of the original size

So, under linux, this is how i would convert all BMPs into webp images, I think it is exectly the same on windows

on the command line, the command for compressing one image looks like

cwebp -lossless 00.bmp -o 00.webp

Now, the next step is to run them in a batch, copy the following text into a file and name it with the extension

To install Hyper-v, you typically open the add features menu in windows and add Hyper-v, this works in Windows Pro, but does not work in windows Home

In Windows Home, it is a very simple process

Create a file and name it (hv.bat), mind you, this is the whole name, where bet is the new file extension, make sure you don’t have an hv.bat.txt undreneath (Make sure windows is showing you the extensions)

Now, All you need to do is put the following text in the batch file (hv.bat), then Run it as administrator

     pushd "%~dp0"
     dir /b %SystemRoot%\servicing\Packages\*Hyper-V*.mum >hv.txt
     for /f %%i in ('findstr /i . hv.txt 2^>nul') do dism /online /norestart /add-package:"%SystemRoot%\servicing\Packages\%%i"
     del hv.txt
     Dism /online /enable-feature /featurename:Microsoft-Hyper-V -All /LimitAccess /ALL
     pause

Once done, the command prompt will ask you whether you would like to restart your computer to apply changes, I would suggest you respond with N (For no) and take your time closing all your applications etc… then restart manually

Right after the restart, hit the windows key on your computer, and type hyper-v, the application should appear and you can run it, it works just like it does on the pro version

Happy computing 😉