Emily Locke lemonieLemonie

A guide to writing a language grammar (TextMate) in Atom

Tree sitter

Atom is transitioning to an entirely new way of defining grammars using tree-sitter. This will be enabled by default quite soon now. It is theoretically faster and more powerful than regex based grammars (the one described in this guide), but requires a steeper learning curve. My understanding is that regex based grammars will still be supported however (at least until version 2), so this guide can still be useful. To enable it yourself, go to Settings -> Core and check Use Tree Sitter Parsers

Links for tree-sitter help:

tree-sitter: the main repo
tree-sitter-cli: converts a JavaScript grammar to the required C/C++ files
node-tree-sitter: module to use Tree-sitter parsers in NodeJS
[My guide on starting a Tree-sitter grammar

Encoding high-quality HEVC content with FFmpeg - based NVENC encoder on supported hardware:

If you've built ffmpeg as instructed here on Linux and the ffmpeg binary is in your path, you can do fast HEVC encodes as shown below, using NVIDIA's NPP's libraries to vastly speed up the process.

Now, to do a simple NVENC encode in 1080p, (that will even work for Maxwell Gen 2 (GM200x) series), start with:

ffmpeg  -i <inputfile>  \
-filter:v hwupload_cuda,scale_npp=w=1920:h=1080:format=nv12:interp_algo=lanczos,hwdownload \

-c:v hevc_nvenc -profile main -preset slow -rc vbr_hq \

Encoding high-quality HEVC content in a two-pass manner with FFmpeg - based NVENC encoder on supported hardware:

If you've built ffmpeg as instructed here on Linux and the ffmpeg binary is in your path, you can do fast HEVC encodes as shown below, using NVIDIA's NPP's libraries to vastly speed up the process.

Now, to do a simple NVENC encode in 1080p, (that will even work for Maxwell Gen 2 (GM200x) series), start with:

ffmpeg  -i <inputfile> -pass 1 \
-filter:v hwupload_cuda,scale_npp=w=1920:h=1080:format=nv12:interp_algo=lanczos,hwdownload,format=nv12 \

-c:v hevc_nvenc -profile main -preset slow -rc vbr_2pass \

Compilation FFMpeg / NVENC + NVRESIZE + QSV + VAAPI + VDPAU + OpenCL

This gist will help you to compile ffmpeg with NVENC, QSV, VAAPI, VDPAU, and OpenCL support.

nVidia nvresize patch is outdated and not more compatible to the latest version of FFmpeg, so it's not included in this documentation.

(even if I've passed a lot of time at trying to make it compile... without any success)

Please don't rely on this page: https://developer.nvidia.com/ffmpeg, the implementation is a hack and was never been added to the main FFmpeg tree.

Useful Examples of ffmpeg and GNU parallel on the command-line:

Transcoding FLAC music to Opus:

ffmpeg is a highly useful application for converting music and videos. However, audio transcoding is limited to a a single core. If you have a large FLAC archive and you wanted to compress it into the efficient Opus codec, it would take forever with the fastest processor to complete, unless you were to take advantage of all cores in your CPU.

parallel 'ffmpeg -v 0 -i "{}" -c:a libopus -b:a 128k "{.}.opus"' ::: $(find -type f -name '*.flac')

Transcoding Videos to VP9:

Spawning multiple ffmpeg processes with xargs:

On standard NVIDIA GPUs (Not the Quadros and Tesla lines), NVENC encodes are limited to two simultaneous sessions. The sample below illustrates how to pass a list of AVI files to ffmpeg and encode them to HEVC on two encode sessions:

$ find Videos/ -type f -name \*.avi -print | sed 's/.avi$//' |\
  xargs -n 1 -I@ -P 2 ffmpeg -i "@.avi" -c:a aac -c:v hevc_nvenc "@.mp4"

This will find all files with the ending .avi in the directory Videos/ and transcode them into HEVC/H265+AAC files with the ending .mp4. The noteworthy part here is the -P 2 to xargs, which starts up to two processes in parallel.

FFmpeg and libav's playbook: Advanced encoding options with hardware-based acceleration, NVIDIA's NVENC and Intel's VAAPI-based encoder.

Hello guys,

Continuing from this guide to building ffmpeg and libav with NVENC and VAAPI enabled, this snippet will cover advanced options that you can use with ffmpeg and libav on both NVENC and VAAPI hardware-based encoders.

For ffmpeg:

	# inspired by https://gist.github.com/rjnienaber/af47fccb8410926ba7ea35f96c3b87fd

	# remove bundled ImageMagick
	sudo apt remove imagemagick -y

	# install base dependencies
	sudo apt-get install -y \
	build-essential \
	git \
	libde265-dev \

	Encoder hevc_nvenc [NVIDIA NVENC hevc encoder]:
	General capabilities: dr1 delay hardware
	Threading capabilities: none
	Supported hardware devices: cuda cuda d3d11va d3d11va
	Supported pixel formats: yuv420p nv12 p010le yuv444p p016le nv16 p210le p216le yuv444p10msble yuv444p16le bgr0 bgra rgb0 rgba x2rgb10le x2bgr10le gbrp gbrp10msble gbrp16le cuda d3d11
	hevc_nvenc AVOptions:
	-preset <int> E..V....... Set the encoding preset (from 0 to 18) (default p4)
	default 0 E..V.......
	slow 1 E..V....... hq 2 passes
	medium 2 E..V....... hq 1 pass

	#!/bin/bash

	# for a blogpost on this, check: http://www.aktau.be/2013/09/22/detecting-interlaced-video-with-ffmpeg/

	# detect interlacing with the ffmpeg "idet" filter, the longer
	# you let this run, the better, though it's never 100% accurate

	# flags:
	# -an = discard audio, we don't need it
	# -f rawvideo = output raw video