Why OpenShot will Not Run on my Linux Tablet

In This earlier posting, I had written, that although I had already deemed it improbable that the sort of Linux application will run on my Linux tablet, I would nevertheless try, and see if I could get such a thing to run. And as I wrote, I had considerable problems with ‘LiVES’, where, even if I had gotten the stuttering preview-playback under control, I could not have put LiVES into multi-tracking mode, thereby rendering the effort futile. I had also written that on my actual Linux laptop, LiVES just runs ~perfectly~.

And so a natural question which might come next would be, ‘Could OpenShot be made to run in that configuration?’ And the short answer is No.

‘OpenShot’, as well as ‘KDEnlive’, use a media library named ‘mlt’, but which is also referred to as ‘MeLT’, to perform their video compositing actions. I think that the main problem with my Linux tablet, when asked to run such applications, is that it is only a 32-bit quad-core, and an ARM CPU at that. The ARM CPUs are designed in such a way, that they are optimal when running Dalvik Bytecode, which I just learned has been succeeded by ART, through the interpreter and compiler that Android provides, and in certain cases, at running Codecs in native code, which are specialized. They do not have ‘MMX’ extensions etc., because they are RISC-Chips.

When we try to run CPU-intensive applications on an ARM CPU that have been compiled in native code, we suffer from an additional performance penalty.

The entire ‘mlt’ library is already famous, for requiring a high amount of CPU usage, in order to be versatile in applying effects to video time-lines. There have been stuttering issues, when trying to get it to run on ‘real Linux computers’, though not mine. My Linux laptop is a 64-bit quad-core, AMD-Family CPU, with many extensions. That CPU can handle what I throw at it.

What I also observe when trying to run OpenShot on my Linux tablet, is that if I right-click on an imported video-clip, and then left-click on Preview, the CPU usage is what it is, and I already get some mild stuttering / crackling of the audio. But if I then drag that clip onto a time-line, and ask the application to preview the time-line, the CPU usage is double what it would otherwise be, and I get severe playback-slowdown, as well as audio-stuttering.

In itself, this result ‘makes sense’, because even if we have not elected to put many effects into the time-line, the processing that takes place, when we preview it, is as it would be, if we had put an arbitrary number of effects. I.e., the processing is inherently slow, for the eventuality that we’d put many effects. So slow, that the application doesn’t run on a 32-bit, ARM-quad-core, when compiled in native code.

(Updated 10/09/2017 : )

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Google Pixel C does not have NEON.

I have been thoroughly enjoying my Google Pixel C, which I ordered only recently, and which I ordered because the actual tablet I have been using before, was only a first-generation Samsung Galaxy Tab S.

Sometimes we obtain many new features, but also at the expense of losing some feature. Because the ARM CPU is a RISC-Chip, the manufacturers of Android devices have sometimes made up for this by including a coprocessor called NEON. NEON is an SIMD – a Single-Instruction, Multiple-Data – coprocessor – aka a Vector-Processor, which is often useful to allow the decoding of high-definition video streams in real-time, without placing the burden of doing so on the main CPU.

(Edit 04/08/2017 : I have given my own definition of what “Hardware Acceleration” means, Here. )

What has happened with the Pixel C, is that Google has decided to put a Tegra X1 CPU into it, which is an SoC that also has a big coprocessor – its mighty GPU. With this tablet, real-time video-decoding is meant to be performed by the GPU, which advertizes several system-installed Codecs. Therefore, watching videos in high definition should not require a NEON coprocessor, and the Tegra X1 does not have one. (And, when I scroll further down the list of Codecs, that list includes two of the corresponding Encoders, from Nvidia, not only the Decoders. )


In fact, the Pixel C only has a 4-core main CPU!

Continue reading Google Pixel C does not have NEON.