By Arnon Weinberg, on May 30th, 2022
Machine learning algorithms for video processing typically work on frames (images) rather than video.
In a typical use-case, FFmpeg can be used to extract images from video – in this example, a 50-frame sequence starting at 1:47:
>ffmpeg -i input.vid -vf “select=’gte(t,107)*lt(selected_n,50)'” -vsync passthrough ‘107+%06d.png’
Omit the -vf option if extracting the entire video. . . . → Read More: Using FFmpeg to replace video frames
By Arnon Weinberg, on May 20th, 2022 Preserving Data
Running a simple FFmpeg filter command:
>ffmpeg -i input.vid -filter_complex “[v:0]copy” output.vid
… one might expect the output video to be the same as the input video. Note that both input and output videos use the same container format (file name extension), and the command just uses the “copy” (do nothing) filter, . . . → Read More: FFmpeg lossless filtering
By Arnon Weinberg, on January 31st, 2015 While Google promotes HTTPS Everywhere, browsers have been working with a certifying authority oligopoly for many years promoting and enforcing an industry based on perception.
https: The good and the bad
The ‘s’ in https stands for ‘secure’ and indicates use of the SSL or TLS protocol. The SSL protocol serves 2 primary purposes:
Verification: . . . → Read More: https and the browser conspiracy
By Arnon Weinberg, on June 25th, 2014 Our servers were attacked recently by a constant stream of HTTP POST requests. The requests were coming in from a large range of IP addresses, at a rate of about 5-10 per second, with random POST data. However, all the requests had the same UserAgent, they always accessed the non-www form of the same domain, . . . → Read More: HTTP DDoS: “Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)”
By Arnon Weinberg, on October 8th, 2012 This guide examines setting up chroot’ed SFTP-only user accounts under Virtualmin.
The Rationale:
SFTP is a secure alternative to FTP and FTPS that uses SSH. With this setup, no FTP server is needed, as the native sshd server is used instead, SSH does not require an SSL certificate (like FTPS), and is usually considered more . . . → Read More: Virtualmin + SFTP + chroot
By Arnon Weinberg, on March 15th, 2011 Tracking down the source of a memory leak in Linux is not always straightforward…
Signs of a Memory Leak:
Typically, the first sign of a memory leak is the oom-killer. If programs start dying inexplicably, check the system log (usually /var/log/messages) for evidence of the oom-killer in action. This should be accompanied by low memory . . . → Read More: Linux memory leak detection
By Arnon Weinberg, on February 7th, 2011 Say you want to install a program in Fedora…
Before Compiling:
Many programs are available easily in the Fedora repositories via yum.
If you don’t already have a graphical package management tool, then install PackageKit or yumex. If you prefer the command-line, then (as root / under sudo) use: >yum search <program> to see if . . . → Read More: Compiling programs in Fedora
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