Voyandz

Voyandz is a real-time AV streaming server akin to the discontinued ffserver. Its primary purpose is to enable network streaming of audio, video or audio & video in form of continuous, non-seekable streams. The source feed can be any feed that can be provided in a streamable form through a preinstalled program such as ffmpeg. The output stream can be any stream that can be produced by a preinstalled program such as ffmpeg. Voyandz itself doesn't delve into codec details, but merely deals with piping.

ffmpeg not attached.

Home page: https://github.com/Zalewa/voyandz/

Installation

  pip3 install voyandz

Then run:

  voyandz -h

Current State

At current stage voyandz is already usable. It is possible to prepare configuration file that will create a usable pipeline. HTTP clients, such as browsers or command line downloaders, can be used to connect to stream endpoints and download the data produced by voyandz. voyandz will work with as many input feeds and HTTP clients as possible until it hits soft limits such as CPU power or throughput.

It is currently untested how voyandz will behave during long-time operation or under heavy usage.

What works

• Home page, stats page - HTML, config dump - dumps config in JSON format.
• Reading and parsing a config-file with defined streams and feeds.
• Piping feeds to streams and then to HTTP clients; creating pipelines.
• YAML configuration files allowing to define transcoding commands, mimetypes, client exclusive or shared streams, listen port, listen host.
• A "screenshot" stream that produces one picture and closes connection.
• Logging stderr of commands to a configured logdir.

Unstable

• Config format.
• API.

TODO

• Config documentation.
• Config command templating; command args; allow to declare multiple similar feeds and streams without having to copy and paste the same text all over the config file.
• Code documentation (docstrings).
• Limit stderr logfiles to a set size, even though it should be logrotate's job.
• Daemon mode (in the systemd era, should I even be concerned?)
• Dead feed resurrection.

Development

Requirements:

• Python 3
• virtualenv
• make (optional)

Create virtual env, install dependencies, link the application:

  python3 -m venv venv
  . venv/bin/activate
  make init
  make dev

To start in development mode:

  FLASK_ENV=development voyandz -f config/minimal

Cleaning:

  make clean
  rm -rf venv

Repository Structure

Project file structure should adhere to the practices recommended for Python and Flask projects.

The src layout is used.

  .
  |- config - example configuration files
  |- sandbox - development scraps, experiments
  \- src/voyandz - application code

Name

The name is voyandz, all lower-case. V stands for video, A stands for Audio, the rest is gibberish.

Troubleshooting

Problem: Running on Linux and getting "cannot modify pipe size: [Errno 1] Operation not permitted" error upon heavy load.

Solution:

voyandz makes extensive use of pipes. To improve piping performance, the size of those pipes is increased using F_SETPIPE_SZ fcntl calls. However, Linux kernel imposes a limit on non-root users on how much memory can be consumed by the pipes by each user. This limit is controlled through a kernel parameter

  fs.pipe-user-pages-soft

The value of this parameter is expressed in pages, which means the total allowed size is at least 4kB times this value. You can read more at: https://patchwork.kernel.org/patch/8055531/

voyandz will continue to operate even if the limit is breached, but all pipes that try to go above the limit will actually be limited to the size of one page. Once usage drops and old pipes are closed, new pipes recover the capability to increase their sizes.

To allow more pipes to be opened with increased size do one of those:

• sudo sysctl fs.pipe-user-pages-soft=65536 to increase the limit; Choose a value right for you if you think 65536 is still not enough.

• sudo sysctl fs.pipe-user-pages-soft=0 to disable the limit completely

To persist this value between reboots add it to /etc/sysctl.conf or /etc/sysctl.d/.

More info: http://man7.org/linux/man-pages/man7/pipe.7.html

Keywords: pipe-user-pages-soft, PermissionError, Operation not permitted