A caveat in using ‘ffmpeg’ to produce consumer-ready streams, from individual frame-files.

It recently happened to me, that I had used ‘Blender’ to create a very short animation, with 144 frames, but where I had instructed Blender to output this animation as a series of numbered .PNG-Files, which I would next use an ‘ffmpeg’ command, to compile into a compressed stream, the latter being an .MP4-File, using H.264 video compression. ( :1 )

But unexpectedly, I had obtained an .MP4-File, which would play on some of my player applications, but not on others. And when I investigated this problem, I found that player-applications which used a feature under Linux named ‘VDPAU‘, were Not able to play the stream, while player-applications which used software to decompress the stream, were able to play it.

The very first assumption that some people could make in such a situation would be, that they do not have their graphics drivers set up correctly, and that VDPAU may not be working correctly on their Linux-based computers. But, when I looked at my NVidia settings panel, it indicated that VDPAU support included support for H.264 -encoded streams specifically:

screenshot_20180720_154326

BTW, It’s not necessary for the computer to have an NVidia graphics-card, with the associated NVidia GUI, to possess graphics-acceleration. It’s just that NVidia makes it particularly easy, for users who are used to Windows, to obtain information about their graphics card.

Rather than to believe next, that VDPAU is broken due to the graphics driver, I began to look for my problem elsewhere. And I was able to find the true cause for the playback-problem. Ultimately, if we want to compress a stream into an .MP4-File, and if we want the recipient of that stream to be able to play it back, using hardware-acceleration, which is the norm for high-definition streams, then an ‘ffmpeg’ command similar to the one below would be the correct command:

 


ffmpeg -framerate 24 -i infile_%4d.png -an -vcodec libx264 -pix_fmt yuv420p -crf 20 outfile.mp4

 

But I feel that I should explain, how my first attempt to compress this stream, failed. It did not contain the parameter shown above, namely ‘-pix_fmt yuv420p‘. There are two WiKiPedia articles, which explain the subject of what ‘YUV’ means, and that may explain the subject better than I can, and that I recommend my reader read:

https://en.wikipedia.org/wiki/YUV

https://en.wikipedia.org/wiki/Chroma_subsampling

I am now going to paraphrase, what the above articles explain in detail.

Continue reading A caveat in using ‘ffmpeg’ to produce consumer-ready streams, from individual frame-files.

Are Chromosomes Magnetic?

It’s a valuable asset to Scientists as well as other analytical thinkers, to be able to distinguish between ionizing and non-ionizing radiation.

Ionizing radiation won’t just alter some molecules within the human body, but will alter any molecule in our bodies, including genes. And this last phenomenon, is one reason for which ionizing radiation, at low, prolonged exposures, causes an increase in the risk of cancer. This includes neutrons and gamma-rays, but also, if originated within the body, alpha and beta radiation as they were originally named: Energetic Helium Nuclei and Electrons.

On the other hand, radio-waves including microwaves are non-ionizing radiation. This means that although in some cases correlation with leukemia and other cancers were noted, nobody has yet explained how radio-waves and microwaves could cause cancers, because we don’t really know what these waves do within our bodies, other than ‘To increase the amount of vibration between our molecules.’ This last excuse is quite non-factual, because the very temperature of our bodies is already causing its molecules to vibrate. Hence, an adult male who takes a 10 minute bath in 40⁰C hot water, is unlikely to be able to conceive directly afterward, but also won’t get leukemia either.

And yet, the simple fact that we don’t know the explanation for a phenomenon, is not itself proof that the phenomenon does not exist, or that it never takes place.

What caused me to pause and think, was the fact that women are considerably more likely to develop breast-cancer in their left breasts, than they are in their right breasts. Why would that happen? I’ve seen people pounce on such explanations, as the fact that statistically, woman’s left breasts are also slightly larger than their right breasts. But in fact, this sort of explanation is equally nonsensical, because on the average, woman’s left breasts would need to be at least twice as large as their right breasts, in order to cause such a large deviation. Are they?

A basic question which I’d like an answer to next would be, ‘Is it possible that actual genetic material, such as chromosomes, are paramagnetic?’ If they are, then they will be vibrating in response to EMFs, radio waves and microwaves, much more strongly, than the rest of the cell’s physical substance, and more strongly, than as a result of thermal agitation alone.

I think that what most right-handed people tend to do – who wear shirts – is just to slip their cell-phones into their left shirt-pockets.

(Update 07/21/2018 : )

Continue reading Are Chromosomes Magnetic?

Planned Power Cut Today

One of the subjects I wrote about in past months, was that My power utility had been planning to cut power to my home, briefly, to perform work on the -distribution system. This had to do with our wireless power meters, that needed to be replaced.

Because the linemen knocked on my door, and forewarned me of the power cut, in order to avoid any file-system corruption, I actually shut down all my computers, one of which acts as my Web-server.

As a result of my shutting the computers down, my site and blog were off-line from about 13h30 until 14h20 this afternoon. I apologize for any inconvenience to my readers.

The actual power-cut only lasted approximately 5 minutes, but because I did not know the exact timing with which it would take place, I was cautious and shut down my computers at 13h30 already.

This time around, the X-server on the computer named ‘Phoenix’ took 2 attempts to restart.

At least this power-cut resolved an outstanding issue.

Dirk

 

Major Update, On Computer ‘Plato’

(As of 20h30 : )

One fact which may confuse some of my readers, is that I have more than one computer. The server of my Web-site and blog, is a Debian / Jessie, Debian 8 system called ‘Phoenix’.

But a much-more interesting computer is a Debian / Stretch, Debian 9 system called ‘Plato’. That is an early, 8-core machine with 12GB of RAM, which does not act as much of a server, but that has an NVidia GeForce GTX460 graphics card, with proprietary drivers.

This evening, ‘Plato’ received a set of updates, that both upgraded its Linux version from Debian 9.4 to Debian 9.5, as well as upgrading its graphics drivers. Aside from some minor misbehavior before the required reboot, the updates seemed to take place smoothly. However, I must now test my graphics capabilities, and all things related to its GPU.

‘Plato’ also received an update to its CUDA drivers.

(Update 21h10 : )

On the computer I name ‘Plato’, I can still play the game ‘Quern – Undying Thoughts’ (through my Steam account), and The LuxCore Render still works, which verifies my OpenCL capabilities.

I never did a thorough test of the CUDA capabilities, but because my NVidia control panel still tells me I have 336 CUDA cores, I’m assuming its basic functionality is still intact.

Dirk